Can Robber Screens Reduce Mite Immigration? Part 3

Contents

The Effect of Mite Immigration Upon the Efficacy of OAE. 1

Trial B –– A Comparative Trial of Effect of Robber Screens Upon Mite Buildup. 4

Experimental Design. 4

Materials and Methods. 5

Results. 7

Discussion. 10

Next 10

Acknowledgements. 10

Citations and Notes 1

Can Robber Screens Reduce Mite Immigration?

Part 3

First Published in ABJ September 2024

Randy Oliver

ScientificBeekeeping.com

Concurrent with the field trial of robber screens that I wrote about last month, we ran a completely different sort of test –– to see whether having robber screens in place would increase the efficacy of extended-release oxalic acid (OAE) treatment in late summer.

The Effect of Mite Immigration Upon the Efficacy of OAE

I’ve previously found that extended-release oxalic (due to its relatively slow action) appears to perform best when colonies are located in isolated yards with no other hives in the neighborhood (Figure 1) —the assumption being that the increase in efficacy was due to lack of immigration of mites from other hives.  It occurred to me that I could use this observation to test whether robber screens would improve the efficacy of an OAE treatment.

Fig. 1  In the summer of 2019 I was asked by a grad student to place hives next to high-elevation meadows in the Sierra Nevada (where there were no resident honey bees; our brown hives are barely visible in the background), to see whether adding honey bees to the landscape would have an effect upon the seed set of a native flower (the results were inconclusive).

For the project, we placed hives next to three meadows.  Since there was a good nectar and pollen flow occurring, we expected that the mite infestation rates of the colonies would explode without treatment.  So we took mite wash counts, and treated 45 hives with elevated mite levels with shop towels soaked in 1:1 OA:gly (this was before we discovered the advantage of using thicker matrices).  Nevertheless, the treatments were astoundingly efficacious [[1]].

We were again asked to restock the meadows in 2020, so used the opportunity to test two doses of OAE on Swedish sponges –– either a half sponge (25 g OA) or a full one (50 g OA, 1:1 glycerin).  Despite the colonies engaging in the copious rearing of drones over a long duration, the degree of mite control by the treatments again amazed us (Figures 2 & 3).

Fig. 2  This trial ran from 16 June through 18 August.  Without treatment, the mite counts would have been expected to quadruple (if they had done so, the red columns (ending counts) would have been four times as high as the blue ones).

Fig. 3  We waited even longer to take final wash counts in these two yards (16 June through 1 September).  Note the very high starting counts (from which colonies often can’t recover), going down to zeroes.  Despite that, by the end of 77 days of treatment, the mites had nearly disappeared!

We got similar results (not shown) from a pumpkin pollination apiary that we stocked in an isolated valley in Nevada (ours were the only colonies present) –– instead of the usual major increase in mite infestation that we’d experienced in previous years (with our colonies going downhill), the hives came back strong and full of honey, with mite wash counts of zero.

Practical application:  The results from the above isolated apiaries strongly suggest that OAE treatment can be extremely efficacious when colonies are not exposed to the immigration of mites from surrounding colonies (managed or unmanaged) in the neighborhood.

Trial B –– A Comparative Trial of Effect of Robber Screens Upon Mite Buildup

Experimental Design

The above finding regarding the apparent effect of mite immigration upon OAE efficacy gave me an idea for another way to test whether robber screens would reduce mite immigration –– by seeing whether they would improve the efficacy of an OAE treatment.  We had a number of available test yards near home, surrounded by neighborhoods containing plenty of hobby and feral colonies, from which mite immigration would be expected.

For the trial, I didn’t want the OAE treatment to be so strong as to eliminate any observable impact from immigrated mites, but also didn’t want the mites to build up excessively in the Control hives not receiving robber screens.    So we treated all the hives with only a half dose of OAE.  We knew from previous trials [[2]] that a 25-gram dose of OAE on a half sponge would not be expected to be fully efficacious in our local outyards, especially with the expected immigration of mites from the neighborhoods surrounding our test yards.  My hope was that the low OAE dose would allow the effect of immigrated mites to show in our unscreened Controls, while still holding back mite buildup enough that we could save them once the trial was over.

This experimental design would be an indirect method of testing the effect of robber screens, since we wouldn’t be directly measuring mite immigration.  But since it would save us from performing tedious stickyboard counts, we could include a lot of colonies, and replicate the trial in a number of yards.

Practical application:  This experimental design would actually be more relevant to beekeepers than Trial A, since instead of merely providing incoming mite numbers from stickyboard counts, it would demonstrate whether installing robber screens would improve the efficacy of a treatment with a miticide.

Materials and Methods

We replicated the trial in six yards in the foothills (133 hives in total), in the expectation that the colonies in at least some of the yards would experience appreciable immigration of mites from outside.  We treated every hive with a half sponge to retard mite buildup, but still allow an opportunity for robber screens to prove their benefit over the course of 51 days (from 9 August and 29 September –– a period during which mite populations typically explode in our area) (Figures 4 & 5).

Fig. 4  After first taking mite wash counts from every hive, we flipped a coin to determine which of each adjacent pair of hives would get an entrance screen (wide opening up), adjusting treatment assignment if necessary to even out the starting mite counts.

Fig. 5  Many of our outyards are squeezed into property corners in semi-rural wooded neighborhoods.  In most of the test yards the hives were closely spaced, which would favor between-hive bee and mite drift.  All the test yards were in areas with an abundance of hobby beekeepers and plenty of tree cavities for feral colonies.

We ran the trial for 51 days, after which we took final mite counts to compare to the starting counts.

Results

To our surprise, despite the half-dose OAE treatment, there was very little overall increase in mite infestation in any of the six yards (A – F); in fact the counts actually went down in many of the hives!

Practical application:  This result confirmed our findings from our 2020 trial [[3]] –– that a half sponge would generally “hold” the starting mite count (of unscreened hives) at 50 days.  In retrospect, we should perhaps have applied an even lower dosage (but, my sons aren’t crazy about me allowing mites to build up in hundreds of experimental hives).

Since the mite wash counts were very low and barely increased in the vast majority of the hives (going from an average of 2.3 to 2.4 mites per half cup of bees), I calculated the mean and median absolute changes in count (as opposed to proportional changes) per yard in Table 1.

As usual, the median values are more relevant than the means, because they aren’t influenced by a few wild outliers.  Since the results were similar for all yards, I combined the data in Table 2.

The median values for mite wash counts in Table 2 did not differ between the Control and Screened hives.  More visually, look at a histogram comparing the distributions of counts from the two test groups (Figure 6).

Fig. 6  Since the final mite counts averaged only around 2 mites per half cup of bees. I plotted the distribution of absolute change in mite count (rather than proportional change).  For both test groups, mite counts mostly either did not change, or went up by 5 or fewer mites.  Although the Screened columns are both slightly lower the those for the Controls, they were not significantly different (t-test p = 31%). The distribution of outliers was similar whether screens were installed or not, other than that two control colonies exhibited unusually high ending counts –– perhaps from being highly attractive to drifting bees, or from robbing out collapsing colonies in the neighborhood.

The histogram again suggests that having robbing screens on a hive didn’t make much difference.  Not giving up, I worked hard to try to tease out evidence that the robber screens were of benefit, by graphing the data out in a number of different ways.  For example, I wondered whether there was a relationship between a hive’s starting and ending mite counts (Figure 6).

Fig. 7  Columns going upward from the 0 baseline indicate that the mite count increased, those going downward that it decreased.  There were more changes up or down in hives with higher starting counts (increasing from left to right), but there was no clear correlation between starting mite count and ending count (keep in mind that there can be no decrease in a hive that starts with a zero count), nor obvious benefit from having a robber screen on.  As we’ve found in previous field trials, some colonies are mite drift magnets, and this could be the case for the four hives (two in each treatment group) whose mite counts increased appreciably.

Discussion

I was surprised by the lack of mite buildup across the board.  Could it have been that the half-sponge OAE treatments performed better than expected? Or, as I elaborated on in a recent article [[4]], one factor might have been that we are finally showing some success from our selective breeding program for mite-resistant bees.  This is making it more difficult for me to set up field trials of mite control methods, since I can no longer assume that the mite infestation in a colony will increase without treatment –– I now need to first confirm that any test colony is not innately resistant.

Next

Doing all this work without clear results was frustrating, and try as I might, we’ve so far been unable to produce evidence that robber screens reduce mite immigration.  But I decided to stick with it, and the next year gave robber screens one more chance to prove that they could reduce mite immigration.  Read about it next month!

Acknowledgements

My great appreciation to my helper Rose Pasetes.

Citations and Notes

[1]https://scientificbeekeeping.com/extended-release-oxalic-acid-progress-report-2019/  ABJ December 2019

[2] https://scientificbeekeeping.com/mite-control-while-honey-is-on-the-hive-part-2/ ABJ December 2020

[3] Ibid, Figure 12.

[4] https://scientificbeekeeping.com/selective-breeding-progress-report-2023/ ABJ September 2023

Can Robber Screens Reduce Mite Immigration? Part 2

Contents

Trial A –– A Crossover trial, No Mite Donor Hives 1

Materials and Methods. 2

The Robber Screens Used. 2

The Trial Yard. 3

Preparation for the Trial 3

Experimental Design. 6

Treatment Assignment 7

Stickyboard Counts 7

Results and Interpretation. 9

Conclusions 12

Acknowledgements. 13

Citations and Notes 13

Can Robber Screens Reduce Mite Immigration?

Part 2

First Published in ABJ August 2024

Randy Oliver

ScientificBeekeeping.com

In 2022 we ran two independent and completely different field trials to test whether installing robber screens would be of benefit for reducing the number of mites that hitchhike their way into a hive.

Mites don’t invade a hive on their own –– they need to be carried in on a bee, either a returning forager or robber, or by a drifted or robbing bee from another colony.  In my Mediterranean climate –– where robbing typically doesn’t occur at colony collapse [[1]] –– most mite immigration appears to be due to the normal “drifting” of bees between hives.  The net result is a “diffusion” of mites from colonies with high infestation levels to those with fewer mites, with some colonies appearing to be far more “attractive” to drifted bees than others [[2]].

The Question:  Could installing “robber screens” reduce the amount of bee and mite drift?

Trial A –– A Crossover Trial, No Mite Donor Hives

Materials and Methods

The Robber Screens Used

There are a number of different styles of anti-robbing screens/entrance guards on the market.  For my field trials, I chose to use one manufactured by Beequip in New Zealand (Figures  1 & 2), since I liked several of its features: the simple reversible design (with the option of an offset very small entrance), the fact that they stack neatly for storage in minimal space, and especially that they were made of stainless steel (which would last forever; I have a preference for equipment that I can hand down to my grandkids).  This is not a sales pitch for this product –– I haven’t run any comparative tests of the various robber screens available on the market.

Fig. 1 For this trial, I used the stainless steel RobberGards™ from New Zealand.  These screens can be flipped to provide a full-width top entrance, or a very small offset top entrance.  Due to the high ambient temperatures, for this trial we installed them with the full-width opening, that has a lip below it, which (as you can see) keeps incoming bees from going over it to the entrance.

As with any robber screen, it takes the foragers of a hive a few days to figure out where the entrance is.

Practical application:  Since the “home” bees are eventually able to figure out how to enter the hive, the question then is, will drifting bees (carrying mites) “give up” before they find a way in?

Fig. 2 Any investigating robber or drifted bee would be attracted to the odor emanating through the punched screen, but be unable to directly enter (the assumption being that it would eventually give up).  And even if it attempted to enter from the top opening, it might be met by unwelcoming guards.

The Trial Yard

We set up this trial of robbing screens in one of our yards near town, which had lots of hobbyists and feral colonies in the neighborhood.  In previous years, we suspected that our hives there received considerable mite immigration (a common assumption by beekeepers when their mite wash counts explode late in the season).  We also had a number of our own hives, not involved in the experiment, in the same yard, which got moved out partway through the trial.

Preparation for the Trial

To determine the number of mites being carried into a hive from other colonies (“mite immigration”), one must first attempt to eliminate any resident mites in that colony.  To do so isn’t easy.  In previous immigration studies that I’ve performed, I’ve found a combination of amitraz and fluvalinate to be effective, since we haven’t used any synthetics in our operation for over twenty years (and our mites test to be highly susceptible to amitraz).  So we prepared these test hives by treating them with a combination of Apistan and Apivar strips (to hit them with two different modes of action) (Figure 3).

Fig. 3 We got a late start in preparing for this trial (not beginning until June) –– too late to completely eliminate all the mites by our intended start date in early August.  We applied a combination of Apivar, Apistan, and for good measure, and extended-release oxalic acid pad.

We applied additional fresh miticide strips from time to time, to ensure than any incoming mites would be quickly killed before they could enter a cell to reproduce.  By the time we started taking stickyboard counts in late August, half the hives exhibited daily mite drops of 2 or less, but some were considerably higher.  Since there weren’t any rainy days to see whether their mite counts had dropped to zero (which would have validated that they were essentially free of mites), we checked for the locations of the mites on the stickyboards (Figures 4 & 5).

Fig. 4 In a mite-free hive, most of the fallen mites drop in the outer perimeter of the stickyboard, not in the capping debris beneath the broodnest (the dark rows of debris to the right).  I took this photo in the field, so while I had my magnifying glasses on, I placed pieces of straw pointing to each mite.

Fig. 5 On the other hand, in suspected mite-producing hives, most mites typically fall in the debris beneath the broodnest.

Based upon our experience from counting mites on hundreds of stickyboards, and “getting to know” each receiver hive in various trials, we find the above observation to be consistent.  So unless we get rainy no-flight days for validation, we typically exclude suspect hives from quantification of mite immigration.

Experimental Design

In this trial, we needed to account for the residual mites apparently present in some of the test hives.  Since our objective was not to quantify the absolute value of mites entering, but rather only to see whether installing robber screens would make a difference, I decided to use a “crossover design.”

Crossover design trials are widely used in medical research for testing the effect of drugs or other medical procedures, since they help to account for each subject’s innate differences (health, age, lifestyle, environment, etc.), which make it hard to compare one test group to another (similar to trying compare the results between individual bee colonies).  On way to get around this problem is to randomly divide the test group in two, and have one half take the med each day, and the other half a placebo.  Record any apparent observed effects over a period of time, and then switch their pills to the reverse.  Do this back and forth, so that each subject is observed for any effects of being on the drug versus when off it (without them knowing whether they were on or off).

Practical application:  From previous research, we already knew that there would likely be a huge degree of hive-to-hive variation in mite immigration.  By running a crossover design, each individual hive would toggle back and forth between having a screen on or off, minimizing the variables of hive-to-hive immigration intensity and background residual mite drop.

Treatment Assignment

Most of the hives in the test yard were in set in pairs near each other, so we simply flipped a coin to assign one hive of each pair to either of two treatment groups (A or B), the treatments being either installing a robber screen or leaving the entrance open.  Once we’d collected enough stickyboard counts over time, we then “crossed over” the treatments by swapping the guard to the other hive of the pair (and then later, reversed them again).

Stickyboard Counts

We placed each hive on full-width screened bottoms, with reusable stickyboards made from fiberglass-reinforced plastic (FRP) shower board, on which I draw gridlines with a Marks-a-Lot felt pen [[3]].  This design of stickyboard works very well with a light coating of 1:1 mineral oil: petroleum jelly, and can be used for many years (Figures 6 & 7).

Fig. 6 We set up the bottom boards so that we could pull the stickyboards out from the rear, to avoid disturbing the entrances.  Despite inserting wedges to seal the rear opening, the occasional bee would sneak in (not a problem, since any mites that it was carrying would still likely wind up in the count).

Fig. 7 We pulled the stickyboards twice a week to count the mites.  Even youthful Rose found that using reading or magnifying glasses helped to differentiate mites from the hive debris.  We confirmed the accuracy and consistency of our counts by often recounting the others’ board.

Due to our late start at colony preparation to eliminate their mite, we had to hold off until late August to begin stickyboard counts.  At that time, half the 24 hives were dropping fewer than 3 mites per day, with only two showing over 10 per day (one of which we excluded from the trial [[4]]), leaving us 23 test hives.  Since the objective of this trial was to determine whether the installation of robbing screens would reduce mite immigration (as opposed to quantification of the absolute amount of immigration), the crossover design would correct for any background drop of residual mites.

We wound up recording 18 semi-weekly stickyboard mite counts from 24 hives over the course of 49 days (a total of 432 stickyboard counts), each hive receiving three alternating treatment regimens.

Results and Interpretation

Based upon past observations and assumptions, we expected considerable mite immigration into the hives to occur in the month of September.  That did not occur.  That may be partly due to a miscommunication which resulted in my sons moving the extra hives not in the experiment to another yard on the first of September (which appeared to cause a considerable decrease in the mite drop counts).  Anyway, the low amount of mite immigration made it difficult interpret the results (Figure 8).

Fig. 8 One of each pair of hives was assigned to Group A, the other to Group B (most pairs sitting side by side).  Unfortunately, roughly half the hives exhibited very low mite drop counts over the entire course of the trial (whether or not they had screens on), indicating low mite immigration.  That said, the hives with higher mite drop counts generally exhibited a similar pattern of mite count intensity (apparently due to environmental factors), independent of whether they had screens on or not –– since there was no noticeable change in counts due to reversing the treatments (swapping the screens).  Note: we did not take counts during the cold rain from September 18-22, so any decrease in mite drop during that time period would not show on these graphs.  We also excluded the data from one of the 24 hives, which initially had a very high mite drop count (although its pattern of drops followed the trend).

The data may be clearer if we look at the average semi-weekly counts for each test group (Figure 9).

Fig. 9  Pooling all the counts into group averages, we can look for any overall changes in mite drop counts resulting from a change in robber screens (due to our random treatment assignment, Group A happened to start with higher counts).  Pay attention to the expected inflections up or down (circled), following when screens were installed or taken off.  For the August 29 and September 30 inflections, there didn’t appear to be an effect.  For the September 8 inflections, the slopes were contrary to what one might expect!

Conclusions

As we’d observed in previous experiments, roughly half of the hives exhibited minimal mite drop counts (which made them worthless for looking for a change in immigration due to treatment).  We also noted that there was a major drop in mite counts when potential “mite donor” hives were removed from the yard.

We felt that the results of this trial were frustratingly inconclusive.

Practical application:  Scientific experimentation is a learning process, and we don’t expect to always “get it right” the first try.  So we replicated this trial the next year in another yard, improving the design by starting mite treatment preparation well beforehand (which allowed us to begin the trial earlier in the season), running the trial for a longer duration, moving in collapsing mite-donor hives, and doing an additional crossover swap of screening.

I’ll write about that trial later in this series, but next month I’ll show a different trial that we ran with robbing screens concurrent with the one in this article.

Acknowledgements

My great appreciation to BeeQuip^NZ for supplying the RobberGards, and to Rose Pasetes, for helping me with all the tedious mite drop counting.

Citations and Notes

[1] Oliver, R (2023) A Survey on Robbing at Collapse.  ABJ Feb 2023 https://scientificbeekeeping.com/a-survey-on-robbing-at-collapse/

[2] Oliver, R (2023) A Study on Bee Drift and Mite Immigration: Part 4.  May ABJ https://scientificbeekeeping.com/a-study-on-bee-drift-and-mite-immigration-part-4/

[3] https://scientificbeekeeping.com/scibeeimages/@Citizen-Science-Mite-Drift-Instructions.pdf

[4] This extreme outlier, which although showing mite wash counts of zero, was still dropping over 30 mites a day in late August.

Robbing Behavior in the Honey Bee by Dr. Norm Gary 1966

RVM test

Can Robbing Screens Reduce Mite Immigration?: Part 1

Can Robbing Screens Reduce Mite Immigration?

Part 1

Randy Oliver
ScientificBeekeeping.com

First published in ABJ July 2024

After writing about my investigations into bee drift and mite immigration, I was asked whether the use of robber guards (aka robbing screens) could decrease the amount of mite immigration into hives. So I ran some controlled field trials to find out.

Mite Immigration and Bee Drift

In order for any parasite to survive as a species, it must not only reproduce, but also transmit itself or its offspring to fresh hosts before the original host dies. Not only that, a successful parasite must also spatially disperse to new locations or host populations.

The varroa mite enjoys vertical transmission from a mother hive to a daughter hive when that colony swarms (for the record, it’s the parent queen and a portion of her colony’s adult workers that swarm, leaving behind what will become a daughter colony if one of her daughter queens successfully mates).

Mites can also engage in horizontal transmission when some individuals hitch a ride on a flying bee to a different colony. Such horizontal transmission also results in spatial dispersal of a mite bloodline to different locations than where it was genetically created or the mite was born (hence the rapid spread of varroa after introduction to an area, or the dispersal of miticide-resistant mite genotypes). These rides take place during the mite’s dispersal phase, which occurs between its reproductive phase(es), during which it is trapped beneath the cell capping.

Terminology change: We originally incorrectly used the term “phoretic” to describe mites riding on adult bees. But that term only applies to parasite using a temporary host solely for transportation, without feeding upon it. We’re now using the more accurate term “dispersal” phase.

During this dispersal phase, mites not surprisingly exhibit a preference for riding on nurse bees [[1]], since they not only need to feed upon the well-developed fat bodies of nurses in order to effectively reproduce [[2]], but it is only nurses that stick their heads into the cells of the 5th-instar larvae that a mite must transfer to in order to reproduce.

I find it fascinating that Nolan and Delaplane [[3]] found that mites that have not yet reproduced to exhibit a stronger preference for nurse bees over foragers, than those that have already reproduced at least once. Riding on a forager increases a mite’s risk of death, but may result in them catching a ride to another hive. It appears that evolution has rewarded this risky behavior. In addition, Cervo [[4]] found that the differences in the cuticular odor profiles of nurse vs. forager bees disappeared when their colonies suffered from a high varroa infestation rate –– which increased the proportion of mites riding on workers that exit the hive.

Practical application: Due to the above changes in cuticle odor and behaviors, colonies suffering from a high mite infestation rate become “mite diffusing varroa factories” [[5]], which results in the out-of-hive emigration of mites on the foragers, and immigration (via drifting) of some of those mites into surrounding colonies (into some colonies more than others).

Side Note: An Observation of Potential Varroa Transfer Host?

Varroa destructor relatively recently jumped host species when humans brought Apis mellifera into contact with its native host, Apis cerana. Apis mellifera could now be considered as varroa’s preferred host — at least until European honey bees evolve more resistance to this nasty parasite. Honey bee pupae are the obligate host of varroa –– the only host upon which the mite can reproduce. But the mite also uses adult honey bees as transfer hosts for dispersal, with the advantage that the mite can benefit from being able to feed on its ride.

However, the mite could conceivably use a different animal species as a temporary transfer host, upon which the mite would be called a phoretic, since that host would function solely for mechanical transfer, rather than providing any nourishment to the mite.

Varroa (being blind) choose their appropriate honey bee hosts (whether nurse bee, 5^th-instar larva, or forager bee) by smell. So to abandon its host honey bee and jump onto a different species for phoretic transport, a mite would need to find that other species to be more olfactory-attractive.

I may have observed an example of this very (and previously unreported) behavior last July, when a bee landed on the arm of my assistant Rose Pasetes (not an unusual occurrence). I happened to notice that a varroa mite immediately abandoned that host bee in preference for a human! I whipped out my cell phone to document this surprising phenomenon (Figures 1 & 2).

Fig. 1 I snapped this photo moments after the mite hopped off the bee and onto Rose’s skin. Could we have been witnessing an attempt by a mite to use a human as a transfer host?

Practical application: Paenibacillus larvae, the causative parasite for American Foulbrood disease routinely passively benefits from humans transferring their spores to other hives. Could varroa benefit by actively using us to do the same?

Fig. 2 The mite (visible at 7:00 below the bee) made no effort to feed upon Rose, but also no inclination to return to the bee. Fearful that we may have been witnessing the evolution of a novel means of varroa phoretic behavior, we euthanized the mite. We didn’t have a cup large enough to perform a mite wash, but Rose later confirmed that she was not hosting any additional phoretic mites.

Practical application: I was briefly involved in a mosquito-breeding laboratory in Brazil, where there were numerous female technicians. Some of the gals were clearly mosquito magnets, whereas others were unattractive to the bloodsuckers, again presumably due to their particular skin scent. We need to pay attention to determine whether varroa is evolving to take advantage of beekeepers as hosts for phoretic transmission!

On to robbing screens

OK, potential varroa transmission averted, let’s move onto how it might help to use robbing screens to decrease the immigration of mites into hives. I’ve previously written extensively on the subjects of bee drift and mite immigration [[6]].

Bee behavior: Scouts and foragers do use vision to identify potential floral sources of nectar, but it’s even easier for them to simply scout the neighborhood for a particular scent that they’ve associated with a nectar reward. And that scent may be emanating from a hive. As far as honey bees are concerned, undefended nectar or honey is fair game. “Robbers” are simply foragers following a floral scent that led them to a hive rather than to a flower (we must remember not to equate a honey bee’s exploitation of a potential food source with the morally repugnant plundering of one group of humans by another; a honey bee is incapable of evil intent).

If you put a window screen in front of a hive entrance, the resident bees will quickly learn to fly around it, whereas scout bees from other hives will show up on the screen where the stream of exhaust air from the hive passes through it –– investigating the source of a floral odor emanating from that hive [[7]].

Using that concept, robbing screens use a screen to separate the path of a hive’s exhaust stream of aromatic air from the location of the hive entrance. This makes it more difficult for scout bees, following the scent of ripening nectar, to find the intentionally offset and reduced entrance of the protected hive. The hope is that potential robbers will just give up trying to get in.

The design of robbing screens

All robbing screens that I’ve seen have similar designs (see some examples in Figures 3-5). All can also generally serve as mouse or shrew guards, and according to some beekeepers (I’d appreciate any observations), reduce predation by yellow jackets.

Fig. 3 Country Rubes sells a “traditional” wood-frame robbing screen using low-air-resistance hardware cloth for its screen (which minimizes any exhaust air being diverted through the entrance hole), and a step that separates the screen from the adjustable top entrance hole. It’s designed to be used on bottom boards that have the beeways flush with the hive body (a handy beekeeper can modify any type of entrance guard to fit their particular hive).

Fig. 4 BeeSmart produces a plastic robbing screen with two adjustable top entrances. This design will fit between extended beeways or on 8-frame hives.

Fig. 5 Beequip^NZ sells a stainless steel Robber Guard, which can be flipped upside down to offer a full-width opening across the top (the block below the guard in this photo was only necessary because I raised the entrance for a stickyboard). Since they were designed for the narrower New Zealand hive width, I did need to use a wedge at one side.

Although there may be some congestion when using a small entrance hole, even strong colonies tolerate them in hot weather in my environment.

Using entrance guards to minimize Mite Immigration during Overt Robbing

If a colony gets severely weakened by the varroa/virus complex while there is any fresh nectar inside, it may be quickly mobbed and robbed by other colonies. Like rats leaving a sinking ship, some of the mites in the collapsing colony may hitchhike rides on invading bees and be taken back to the robbers’ home colony (or colonies) [[8]].

An observation: Last year I was taking regular mite washes from a “mite donor” colony that I was nursing, and then one morning watched it get robbed out in a few hours. Once robbing subsided later in the day, I inspected the colony, now completely emptied of every drop of honey. There were only a few dead bees in front of the entrance (presumably guards that died fighting the robbers). On the emptied combs, there was a softball-sized cluster of presumably young (and hungry) workers that had apparently not engaged in fighting. Curious, I washed a half cup of them. The mite wash count taken two days earlier had been 44; it had now jumped to 117, which suggested that many of the mites preferred to remain on the young resident workers, rather than hitching a ride on a robber.

Practical application: Installing a robbing screen once robbing has begun is futile –– the robbers will quickly figure out how to get in.

Overt vs. Covert Robbing

“Overt robbing” of weak or collapsing colonies is one thing. But low-level “covert” robbing (aka “surreptitious” or “progressive” [[9]] robbing), is when robbers enter a hive without being stopped by the guards, help themselves to some stored nectar (or perhaps beg it from a returning forager), and then take it back home, later returning for more. Covert robbing can occur at a low level. On the other hand, I’ve watched yards of nucleus hives get robbed dry during a strong nectar flow by robbers from (presumably stronger) colonies elsewhere, with no signs of fighting taking place, despite dozens of robbers entering every minute.

Anyway, my data suggest that covert robbing may contribute to mite “diffusion” from high-mite hives to neighboring colonies. Robbing screens can reduce either covert or overt robbing from taking place. So could it be of benefit to install robbing screens on your own hives?

Practical application: A robbing screen does not prevent bees from exiting and reentering their own guarded hive and robbing other hives. Thus, it would not reduce immigration of mites brought back by its own robbers.

However, installing robbing screens on your own high-mite hives may help reduce mite diffusion from them to your low-mite hives. But if you’ve got varroa under control in all your hives, there would be little or no benefit to installing robbing screens, other than to keep your strong hives from robbing any weak ones.

But what if you have neighboring beekeepers or feral colonies with high mite levels?

Practical application: Installing robbing screens on your own hives would not prevent your colonies from robbing neighboring high-mite hives. If you have neighboring beekeepers who do not control their mites, you might benefit from giving your neighbors robbing screens for Christmas.

That’s not to say that robbing screens Couldn’t be of Benefit

Despite the fact that placing a robbing screen on your hive wouldn’t prevent your bees from bringing back mites from other colonies, it is still plausible that installing the devices might reduce mite immigration from drifting bees. (It could also conceivably reduce mite-carrying covert robbers from high mite hives from entering your low-mite hives and leaving their mites behind, but it’s not clear how often that actually takes place).

As detailed in my previous articles, late in the season when mite levels may be high in neighboring colonies, some hives may experience substantial mite immigration on days when the weather is favorable for flight (independent of overt robbing taking place). I found that a substantial amount of bee drift (and thus mite dispersal) can take place between high-mite donor hives and bee-attractive receiver hives up to a half mile away (not all hives are attractive to drifting bees, and some hives in a yard do not experience any mite immigration).

Practical application: I found that there can be a high correlation between incoming drifted bees and mite immigration [[10]], with some hives being far more attractive to drifting bees than others. So mite immigration into at least some of your hives could plausibly be reduced by using robbing guards –– provided that the guards actually prevent drifted bees from entering.

Testing whether Robbing Guards Reduce Mite Immigration

To determine whether installing entrance guards would reduce mite immigration, my helpers and I ran three different trials in 2022 and 2023, involving over 200 hives in total, and eight different apiaries. It wasn’t as easy a question to answer as I hoped it might be. Data collection involved some 300 mite washes and over a thousand stickyboard counts (taken on average twice a week) from mite-zeroed hives [[11]].

Trial A –– Crossover trial, No Mite Donor Hives

In this trial, we tracked mite immigration (via stickyboard counts) in 24 hives over 49 days, half with guards on, half without, swapping the guards back and forth from time to time (crossover design), so that each hive was tested with guards on or off (to account for the expected large degree in hive-to-hive variation in mite immigration, based upon our previous research).

Trial B –– Multiple Apiary Comparative Trial

Concurrent with Trial A, but in six different yards, we took starting and ending mite wash counts from 133 hives, then treated them all with a low-dose OAE (extended-release oxalic acid) pad to reduce mite buildup. We installed robbing screens on half of them (randomly blocked by starting mite count) to see whether having guards on made a difference in their final infestation rates 51 days later.

Trial C –– Crossover trial, With Mite Donor Hives

In this trial, we tracked mite immigration in 28 hives over 95 days, again alternating guards being on or off the test hives. But in this trial, we placed high-mite donor hives adjacent to the test hives to increase the amount of mite dispersal.

I’m out of space, so will continue with our findings next month.

Citations and notes

[1] Xie, X, et al (2016) Why do Varroa mites prefer nurse bees? Scientific Reports 6, 28228

[2] Ramsey, S, et al (2019) Varroa destructor feeds primarily on honey bee fat body tissue and not hemolymph. Proceedings of the National Academy of Sciences, 116(5): 1792-1801.

[3] Nolan IV, M & K Delaplane (2017) Parasite dispersal risk tolerance is mediated by its reproductive value. Animal Behaviour 132: 247-252.

[4] Cervo, R, et al (2014) High Varroa mite abundance influences chemical profiles of worker bees and mite–host preferences. Journal of Experimental Biology, 217(17), 2998-3001.

[5] A Study on Bee Drift and Mite Immigration: Part 1

[6] A Study on Bee Drift and Mite Immigration: Parts 1-6. ABJ February through July 2023

[7] A Survey on Robbing at Collapse. ABJ February 2023

[8] Peck DT & TD Seeley (2019) Mite bombs or robber lures? The roles of drifting and robbing in Varroa destructor transmission from collapsing honey bee colonies to their neighbors. PLoS ONE 14(6): e0218392.

[9] Mangum, W (2012) Robbing: Part 2: Progressive Robbing. ABJ 152(8): 761-764.

[10] A Study on Bee Drift and Mite Immigration Part 5. ABJ June 2023

[11] https://scientificbeekeeping.com/suggested-protocol-to-determine-amount-of-mite-immigration/

Effect of OAV on the Rearing of Brood

Effect of OAV on the Rearing of Brood

Ernie Daley and Randy Oliver

 First published in ABJ June 2024

  I have used OAV (oxalic acid vaporization) for varroa control for over ten years and have wondered whether (1) the treatment could be applied proactively prior to the introduction of package bees, and (2) whether the treatment would adversely affect the development and survival of larvae. So, with guidance by Randy Oliver, I ran a couple of experiments.

SET UP OF EXPERIMENT #1

I wondered whether I could apply oxalic acid vaporization to drawn combs (as a proactive “residual insecticide surface treatment”) to control varroa, applied prior to installing the bees. My first question was whether such a treatment would affect the first round of brood laid by the queen (perhaps due to oxalic crystals in the cells). To answer that question, Randy suggested that I run a test by covering half of a frame of empty brood cells with plastic wrap (to provide a Control group unexposed to OA) and then expose the comb to oxalic acid vaporization. Then afterwards remove the plastic wrap and return the treated comb to the hive for the queen to lay eggs in.

So, in late May I ran two replicates of the test, preparing the combs (Figure 1), then placing each of them in the center of a bee-free hive consisting of a medium super with empty drawn combs on either side, and then applying 2 grams of OA by vaporization (Figure 2).

 Fig. 1 Two frames of empty drawn comb, half wrapped with plastic wrap to provide both a treated Test and an untreated Control group on each comb.

Fig. 2 I used a 110 Volt OA vaporizer to heat two grams of oxalic acid to 315°F to vaporize and disperse it into a medium super containing 10 drawn frames (without bees) with the two Test frames in the center of the box, via a hole in the floor rim.

Ten minutes after applying the OAV, I peeled the plastic wraps off the Test combs, and placed them into individual excluder cages, which I then inserted back into the centers of their hives.  I then introduced a 3-lb package of bees (containing their mother queens, caged for transport) into each hive, after first releasing and confining their queens onto their respective Test combs (Figures 3 &4).

Fig. 3Releasing the caged queen from the package into the excluder cage in which she will be confined.

Fig. 4 The excluder cages (with queens) returned to their colonies.

RESULTS OF EXPERIMENT #1

Three days after confining the queens, I removed the Test frames from the excluder cages, and observing that plenty of eggs had been laid, returned them (uncaged) to their respective colonies. Six days later I observed larvae and capped brood on both Test frames (Figure 5 and 6). There was no noticeable difference in the brood patterns of the OAV and Control halves of the Test frames in either colony.

Fig. 5 Test frame from colony “A” 9 days after pretreatment with OAV showing brood development on both the Control and OAV halves.

Fig. 6 Test frame from colony “B” 9 days after pretreatment with OAV showing brood development on both the Control and OAV halves.

EXPERIMENT #2

Now that I had determined that OA pretreatment did not adversely affect the survival of eggs or newly emerged larvae, I was ready to test whether treatment of combs with eggs and growing larvae already present would affect their survival or development.

To answer this question, Randy suggested that I repeat the first test, but this time with eggs and larvae already present when I applied OAV to the combs.

Working in early July I again used an excluder cage to confine a queen on a frame of drawn comb for six days. When I returned six days after confining the queen, I observed eggs and larvae on both sides of the frame. I then wrapped half of the Test frame with plastic wrap (Figure 7) and returned it to the hive without the excluder cage.

Fig. 7 The Test frame with eggs and larvae 6 days after confining the queen onto the comb, prior to applying OAV. One half is wrapped with plastic wrap to provide a Control group unexposed to OA.

I then applied two grams of oxalic acid by vaporization to the double-medium colony (the usual dosage I would apply when treating a double medium for varroa). Ten minutes after ending the OAV, I removed the Test frame from the hive, peeled off the plastic wrap, and returned it to the colony for 11 days. The ages of the eggs and larvae prior to OA vaporization were 1-6 days.

RESULTS OF REPLICATE #1

Eleven days after the OAV application, I removed the Test frame and inspected both sides for brood survival. There was no noticeable difference in brood survival or development between the OA-exposed and Control halves of the Test frame (Figures 8 and 9).

Fig. 8 Side one of the Test frame 11 days after OAV, showing brood development on both the Control and OAV halves.

Fig. 9 Side two of the Test frame 11 days after OAV, showing brood development on both the Control and OAV halves.
Replicate #2

At Randy’s suggestion, I replicated the experiment with younger eggs and larvae, to see whether I would get comparable results.   I ran this replicate at the beginning of August, using the same double-medium hive. By now the colony had expanded and bees covered fourteen of the twenty frames. I confined the queen as before for 4 days. When I returned 4 days after confining the queen, I observed the queen laying (Figure 10) and eggs (Figure 11) and larvae on both sides of the frame.

Fig. 10 The queen laying an egg on the Test frame on the fourth day of confinement after removal from the excluder cage.

Fig. 11 Eggs and larvae observed on the Test frame 4 days after confining the queen.

As before, I wrapped half of the Test frame with plastic wrap and returned it to the hive. I then applied two grams of OAV, and after ten minutes unwrapped the plastic from the Control side and returned the Test frame to the colony for 13 days. The age of eggs and larvae prior to OAV treatment was 1-4 days.

RESULTS OF REPLICATE #2
When I returned 13 days after OAV application, I removed the Test frame and inspected both sides. Both the OAV and Control halves had similar brood patterns with no observable difference in development or survival (Figures 12 and 13).

Fig. 12 Side one of the Test frame 13 days after OAV showing brood development on both the Control and OAV halves.

Fig. 13 Side two of the Test frame 13 days after OAV showing brood development on both the Control and OAV halves.

DISCUSSION

As far as I could tell there were no adverse effects on the development of eggs or larvae whether brood frames had been pretreated with OAV prior to egg laying, or if OAV was applied when eggs and larvae were already present. The amount of brood, the pattern, and the development on the OAV half of the frame appeared to be the same as that of the Control half in both experiments.

OXALIC RESIDUES FOLLOW UP IN CALIFORNIA (by Randy)

Following the field experiments by Ernie, I was curious as to how much oxalic acid actually remained in each cell after Ernie performed his vaporizations (without or containing larvae).  I calculated how much total surface area there is in a medium super of drawn combs (including the woodenware (top, bottom, and sides) and ten frames (tops, bottoms, ends, and faces of combs): it worked out to 3736 square inches.  Dividing 2 grams of oxalic acid by that area, I got a theoretical result of 535 micrograms (µg) per square inch of surface area (83 µg pr cm²), or 23 µg per cell face.

Note on titrations:  I’ve done extensive work (as yet unpublished) on quantifying the amounts of oxalic acid on bees’ bodies after treatment with oxalic acid applied by different methods.  Since titration doesn’t identify the actual type of acid, my microgram values are for “OA equivalents.”

The theoretical dose from the registered application methods is ~100 µg per bee, but that amount is seldom achieved in the field.  An actual dose of ~30 µg per bee will kill mites.  An adult bee can handle 200 µg of oxalic acid applied as a dribble, but the theoretical 23 µg per cell face may have the potential to affect a newly-emerged larva.

So along with my helpers Rose Pasetes and Corrine Jones, we ran six separate tests on different days, each time applying 2 grams of oxalic acid by vaporization (using a ProVap 110) to different deep supers (since I didn’t have any mediums) of empty drawn brood comb (for which there would be theoretical residues of 17 micrograms per cell face).  We first confirmed that there were no preexisting acid residues in the cells by using a pipette and indicator solution.

Run 1, with plastic squares on the comb faces

For our first run, we also pressed 1 cm² pieces of plastic (cut from a deli container) into the comb surfaces to quantify the amount of residues on the comb surface to compare to the residues inside the cells.

After allowing a half hour for the OA vapor to settle, we removed the treated combs and again used a pipette to test haphazardly-chosen cells for acid residues (measured in OA equivalents) (Figure 14).

Fig. 14 We dropped 5 drops of indicator solution into each cell to test, then sucked it back out with a pipette.  Here, in a practice run, Rose has placed a Control drop in the center, and drops from tested cells around it.  The indicator dye turns green and then orange relative to the amount of acid residues. To our surprise, there were only 1-2 micrograms of OA equivalents per cell, and only 0-10 µg per cm² on the plastic test squares –– far less than the expected 83 µg!

Out of curiosity, I scooped some beebread out of three cells, knowing that bees use lactobacilli to preserve pollen with lactic acid.  The scoops of beebread titrated at 450, 360, and 860 µg OA equivalents of acidity!  Although lactic acid is not quite as reactive as is oxalic, it helps to explain how bees can tolerate treatment with OA.

Anyway, the low amounts in the cells and on the plastic surprised us, and when we later lifted the treated box, we noticed that a portion of the OA had crystallized at the entrance where the stream of vapor hit the bottom board (Figure 15).

Fig. 15 This pile of OA crystals amounted to only a fraction of a gram, but shows that it is important for anyone applying OAV to make sure that the stream of vapor does not directly hit anything inside the hive!

So we ran five more experiments:

Run 2, with dead bees pinned to the combs

In Run 2 we pinned dead bees on the combs (Figure 16) to compare the amount of OA that accumulated on each bee to the amount that we’d previously found when we titrated  bees from clusters after OAV treatment (there is typically ~10 µg per bee shortly after application).

Fig. 16 We pinned dead bees to the combs to see how much OA stuck to them as opposed to the plastic squares used in the first run.  See Fig. 17 for the results.

Fig. 17 The reference tube it to the left.  Most bees had less than 5 micrograms, but the yellow one tested at 60.  There was surprising variation, despite them all having been placed between central combs well above the vapor stream. Again we titrated minuscule levels of OA in the cells.

Run 3, with a handful of live bees loose on the combs.

So I decided to put a handful of young live bees loose on the ten combs of a different super.  I plucked off a batch of them ten minutes after OAV application (Figure 18), and then ten more after they had walked on the combs for an hour (Figure 19).

Fig. 18 At 10 minutes post application, most bees exhibited only slight amounts of acidity, although a few titrated at 40-50 microgram equivalents.  Again, surprisingly wide variation for a treatment applied as a fog.

Fig. 19 But by an hour, all the bees had picked up much more oxalic acid, presumably from walking over the treated comb surfaces.

Run 4, with a tiny cluster of live bees

Still intrigued by our findings, we went out to a stack of recently brought-home deadout supers to look for a cluster of dead bees to test, and to my surprise found a hand-sized cluster of live bees with a queen between the upper portions of two combs.  So we placed that box between a bottom board and cover, and applied 2 grams of OAV (Figures 20- 24).

Fig. 20 When we removed the cover after 10 minutes, we could immediately see that the bees had a “dusting” of white oxalic microcrystals on their setae (“hairs”).

Fig. 21 The bees were far more “frosty” looking than after a normal vaporization.

Fig. 22  A close up of a typical bee from the previous photo covered with oxalic acid crystals ‑‑ far more than I see when I OAV a full-sized cluster!  I hesitated to titrate them…

Fig. 23 I only titrated the first three bees, since it took so many drops of titrant.  Their OA equivalents were 630, 1330, and 150 micrograms!  I have no idea as to why this tiny cluster of bees got hit so heavily by exactly the same vaporization that we’d been giving for the other test runs.

Fig. 24 The cells also contained far more acidity than in the other runs: ranging from 5 to 20 micrograms. Go figure!

Intrigued again, we performed yet another experiment.

Run 5, live bees in push-in cages

This time I placed a few live bees into each of several push-in cages (wide Mason jar lids with 1/8” screen), located between different combs, near the top, and again applied the same amount of OAV via the entrance.  The results are shown in Figure 25 and Table 1.

Table 1 The acid residues on the bees were higher than those for Runs 2 and 3, but far less than those in Run 4.

Fig. 25 Despite the relatively-high amounts of acid on the caged bees, the amounts of residues in the cells were again barely detectable (reference drops below, test drops from the combs above).

Conclusions

To our great surprise, in the five experimental runs –– using the same vaporizer on the same stand, with nearly-identical boxes of combs –– there were large differences in the amounts of acid residues on bees on the combs, and within the cells.  The amounts of acid on the bees was generally far more that I observe when I’ve titrated full hives (mostly 8-10 frame clusters).  So I’m not surprised that Ernie did not observe any adverse effects from OAV upon eggs or larvae.

Experiment 6, Live bees introduced after vaporization

At this point of time, I realized that we hadn’t yet addressed Ernie’s first objective –– to determine whether he could preload boxes of drawn comb with oxalic acid by vaporization, prior to installing a package of bees, for the purpose of killing mites on the introduced package bees.  This was based upon the assumption that the acid residues on the combs would transfer to the bees.  The results of Run 3 certainly indicated that they would.

So we ran yet another experiment.  We again set up a box of acid-free drawn brood combs and vaporized it with 2 grams of oxalic, then allowed it to sit for an hour for all the acid to settle.  We then shook bees from an untreated colony, and confirmed by titration that they were free of acidity.  We allowed any older bees to fly off to ensure that when we introduced them onto the treated combs, that they would remain in the new “hive.”  We introduced a cupful of the presumably young bees, replaced the hive cover, and allowing them to remain in the “hive,” freely walking on the combs.  We took samples of them after 10 minutes, 1 hour, and two hours (by which time their acid levels ceased increasing (Table 2).

Table 2. Similar as in Run 3, the acid levels of the bees increased during the first hour, and then stabilized.  Our finding:  Bees can readily “pick up” a substantial amount of OA microcrystals by walking over treated combs for an hour.

Experiment 7, to be done

The acid levels on the bees above would be plenty to kill mites –– provided that the acid crystals were distributed over the bees’ bodies.  But in a prior preliminary experiment I had found that acid residues of this level, when only on the bees’ feet, did not cause any varroa mortality in an incubator trial.  Unfortunately, by this time it was already November and my dang sons had already treated any hive with measurable mites, so we need to wait until next season to test Ernie’s assumption –– which we’ll do by comparing mite drops on stickyboards after introducing high-mite packages to boxes of treated or untreated combs.  If anyone wants to join us in performing this experiment, we’d love to see your results!

ACKNOWLEDGEMENTS

I wish to thank Randy Oliver for his mentorship, assistance in experimental design, and the writing of this article.  And we thank Rose and Corrine for their help with all the titration experiments.

Time for Plan B?

Time for Plan B?

Randy Oliver

ScientificBeekeeping.com

First Published in ABJ June 2024

 The varroa mite invaded beehives in the U.S. nearly 40 years ago, and has been our major problem ever since. Until mite-resistant stock becomes readily available, we’re stuck with attempting to manage this parasite with an inadequate range of registered products. Keep in mind that the EPA’s mandate is not to help beekeepers, but rather only to prevent the sale or use of any pesticide deemed unsafe. This puts our industry in a frustrating situation regarding legal control of varroa, or (God forbid) Tropilaelaps.

Our situation is that we are dependent solely upon profit-motivated private enterprises (perhaps using research findings by the USDA or universities) to go through the tedious and expensive process of developing new or updated formulated products, and then “proving” to the EPA that they will not pose “unreasonable risk to the environment.”

Practical application: Due to our relatively small market, there is a lack of economic incentive for companies to bring new, reasonably-priced varroacides to market. This, coupled with the EPA’s high fees, abundance of caution, and hidebound bureaucracy, has not only resulted in a paucity of products on the market, but also with the approval and registration of new efficacious products sometimes lagging behind the mite’s ability to evolve resistance. This is not a criticism of the EPA, but rather a problem that I feel that we beekeepers need to proactively address.

As I explained in my article last month, this situation has sometimes left us in the lurch, forcing beekeepers who want to stay in business to creatively use other products not (perhaps yet) approved by the EPA.

Practical application: My fear is that the evolution of amitraz-resistant mites, coupled with enforcement actions by the EPA, is about to leave us in the lurch again. As someone who has long run a commercial operation without amitraz, I can attest that the few registered products currently on the market (save for perhaps the new VarroxSan) may not be up to the job.

Foreseeing this imminent problem approaching, I proactively (and perhaps naively) approached the EPA [[1]], to see whether they would exempt the natural products oxalic, formic, thymol, and food-grade plant oils from regulation for own use (as did New Zealand), since the Agency had already determined that they posed no unreasonable risk to the environment when applied in beehives. This would have allowed us to experiment and use these substances in more colony-friendly and efficacious ways.

A personal clarification: I’ve recently written about upcoming disruptions to our industry [[2]]. Humans are resistant to change. But sometimes it’s important to anticipate change and be proactive. I want to be clear that I have no criticism of any beekeepers, the EPA, or our industry leaders (and don’t want to get involved in politics), but am only trying to help our commercial and recreational beekeepers navigate through a changing world.

But my doing so upset some beekeepers, since they were hoping that if we just kept quiet, the EPA would keep “looking the other way” about their use of “imported” amitraz, despite the fact the Agency has been making very clear since 2022 that that was not to be the case. I apologize to any whom I may have offended, but in my experience, ignoring an imminent problem will not make it go away.

I’ve been talking with folk from the EPA since the infamous bee kill in Germany from neonicotinoid-treated seeds back in 2008, when some beekeepers started vociferously criticizing the EPA’s regulation of insecticides. Something that the EPA folk continually pointed out to me was the hypocrisy of beekeepers criticizing the Agency for not restricting and regulating pesticide use by others, while acting as scofflaws themselves by using Mavrik and Taktic “off label” in their own hives.

But, apparently sympathetic to us (perhaps due to the paucity of registered efficacious varroacides), the Agency appeared to be willing to turn a blind eye, until they got “the letter” from the Association of American Pesticide Control Officials in 2021.

The gears of enforcement action often move slowly, but after receiving that letter, the EPA acted quickly to fire a shot across the bow in 2022, warning us not by targeting beekeepers directly, but rather by busting one of the “suppliers” –– a California couple engaged in smuggling in amitraz products from Mexico (the Agency also monitored online sales offerings and shut them down). And to be sure that they made their point, instead of charging the couple the maximum penalty of $5000 for a pesticide violation, they charged them with conspiracy (although they didn’t yet charge any beekeepers as codefendants) — a violation that carries a maximum penalty of five years in prison and a $250,000 fine.

Despite that warning, beekeeper demand for inexpensive amitraz continued, and others took the risk of being “suppliers.” So the Agency cracked down on another couple in 2023, again charging them with conspiracy. As part of their plea agreement, the defendants agreed that the government could seek the forfeiture of up to $2.2 million in proceeds obtained from the sale of the smuggled goods.

Yet our industry still hungered for unregistered amitraz. So early this year, the Agency again made a show of busting a Central California beekeeper this time –– with a federal grand jury again charging him with conspiring to receive and sell smuggled pesticides into the United States and the unlawful distribution and sale of unregistered pesticides (Figure 1).

Fig.1 A federal grand jury returned a two-count indictment against a beekeeper, charging him with conspiring to receive and sell smuggled pesticides (primarily Taktic and Bovitraz) into the United States and the unlawful distribution and sale of unregistered pesticides [[3]]. An investigation and indictment such as this would have been in the works for some time.

Practical application: The EPA’s been ramping up enforcement action over the past couple of years. Beekeepers had better be thinking about their Plan B if the “normal” supply of amitraz dries up.

Update:  As of September, the EPA has stepped up their enforcement actions.

As far as the EPA is concerned, with their recent registration of Amiflex, there are now two approved amitraz products available to beekeepers, and they made clear in their recent Advisory that if a beekeeper wishes to use amitraz to control varroa, they must use a registered product.

Commercial beekeepers point out that any product applied within the confines of a beehive would exhibit minimal risk to “the environment.” However, the EPA and FDA are justifiably concerned about beekeeper use of unregistered amitraz, since amitraz can indeed potentially pose “unreasonable risk to man,” specifically those handling the raw product, or consumers of honey. Amitraz has the potential to increase reproductive, developmental, and neurological toxicity risks to the general population. The Agency is also concerned that employees handling unapproved amitraz on a long-term basis may increase their risk of cancer. The EPA and FDA are both likely concerned that as mites develop resistance, beekeepers may be tempted to “ramp up the dose,” which could lead to increased levels in honey.

So why question the EPA about clarification?

First a full disclosure: I am not in the least bit critical of beekeepers using amitraz, and have only asked the EPA for clarification regarding the natural products, since the last time that mites developed resistance to a miticide, our industry got left out to dry. Most of my commercial friends have long depended upon Taktic. But several of them have reached out to me in recent years for information on how my sons and I manage to control varroa without amitraz, since that product was no longer doing the trick for them (as well as wanting to get into compliance).

There are several reasons that I started asking the EPA for clarification:

1. I foresaw that beekeepers who have long been accustomed to depending upon Taktic or Bovitraz might see the supply dry up (it looks like this may now be happening).
2. And due to varroa finally developing resistance to amitraz, they were going to need to shift to alternative treatments for mite management anyway.
3. I’m distressed that oxalic acid is not yet registered for use in California [[4]].
4. There is a paucity of registered efficacious thymol and formic products on the market.
5. I personally want to be able to legally use oxalic acid, formic acid, and thymol in my hives using newer and more efficacious application methods than the currently registered products.
6. In my reading of FIFRA, it appeared that the EPA, under FIFRA, should exempt those natural substances from registration, since they had already concluded that they posed no unreasonable risk to the environment.

Practical application: Tropilaelaps is knocking on our door, and we have no products registered for its control. The synthetic miticides appear to be ineffective. Dr. Ramsey has found that formic acid can be efficacious, and I have thymol blocks on the way for testing. If tropi does arrive, we may not have time for a potential registrant to experiment and develop a product, and then go through EPA’s lengthy registration process. I’d hate to get caught with our pants down!

Our right to use products that do not pose risk to the environment

The EPA is strongly pushing agriculturalists to shift toward naturally-derived biopestides and their kin. Since the Agency has already made clear in writing that the application of oxalic acid, formic acid, or thymol in beehives poses no unreasonable risk to the environment, and since those substances are readily available over the counter for everyday use by any homeowner, one could justifiably argue that we beekeepers have the right to use them in our hives.

If a law is unreasonable, people tend to disrespect it. To some of us, the EPA appears to be acting unreasonably regarding our use of these natural, safe (as far as risk to the environment or honey consumer), and inexpensive substances in our hives for varroa management. Thus, I felt that it was in the interest of our industry to formally ask the Agency whether they were exempt from regulation.

In their recent Advisory, the Agency made clear that they were exempting “own use” of them, but they unfortunately left a number of other important questions unanswered, especially with regard to use by commercial beekeepers. Thus I asked our national organizations to formally present some questions to the Agency for clarification.

Our national organizations

I was of course disappointed that our national organizations declined to do so. When I explained to the Office of Pesticide Programs that they were hesitant, I received the friendly reply:

Thanks for reaching out. The Biopesticides and Pollution Prevention Division is the appropriate division to address any follow-up related to the recent beekeeping advisory. There is no “poking the bear” on our end — we are open to hearing feedback, but per [x’s] email, we are looking to the industry associations to consolidate any questions/feedback they are hearing from the industry and provide input on any potential next steps.

The EPA then invited the officers of the ABF and AHPA to an online meeting (from which I and Board members were excluded).

Practical application: As a federal agency, the EPA can be expected to give friendly replies, without clearly answering hard questions. So if you want answers as to what you are “allowed to do” regarding the use of generic oxalic, formic, or thymol, you apparently need to have your “industry association” present the questions to EPA or your State Lead Agency.

So please do not ask me –– contact your association of choice.

Advice from an Australian Secretary of Agriculture

A number of years ago, I was invited to a meeting that a group of Australian beekeepers were having with their Secretary of Agriculture (Figure 2). He told them that he was listening to them only because a sea change had occurred –– up ‘til that point he likened beekeepers to a “herd of cats,” with individuals and little groups approaching the agency with different (and sometimes conflicting) requests. He explained that this allows any governmental official to ignore them. But he told us that on that day he saw all the beekeepers in his state marching in the same direction like a herd of cattle –– resulting in him paying attention to them.

Fig. 2 A typical Aussie apiary in 2010 –– three deeps with a single brood chamber below an excluder. Every week or so, the top super was removed and taken for extraction, with a returning “sticky” then placed under the remaining lower super.

The EPA hears from many individuals and groups, such as farmers, ranchers, the Xerces Society, many litigious environmental groups, and beekeepers from various states. As far as with beekeepers, the Agency has apparently decided that they are going to respond only to our two national organizations (which consist of only a limited number of members, with minimal budgets and volunteer leadership).

Practical application: For some reason, beekeepers in general are loathe to support, seriously fund, and organize one national organization to represent us. In the last issue of this Journal [[5]], my friend Charles Linder (a shaker and mover if there ever was one), compared the beekeeping industry’s representation to government agencies to that of other livestock industries. His article was not a criticism of our national organizations (he and I belong to both), nor their volunteer officers (who do yeomen’s work for the benefit of our industry), nor of their many accomplishments, but simply a call to action for us beekeepers to not only join these associations (or better yet, combine them into a single national organization), but to also reach into our pockets and better fund them.

Although these two organizations have memberships responsible for the majority of managed hives in the country, they represent only a tiny fraction of the number of beekeepers in the country. So let’s do a little arithmetic: There are roughly 2.6 million beehives in the U.S. If every beekeeper donated a single dollar per hive each year to a national organization, that would be the sort of serious money to give us clout in the government!

Possible actions to take

It’s not currently clear to me how strongly our two national organizations are going to push the EPA for answers regarding our use of generic natural treatments (and the Agency will likely confuse things by passing the decision to each state anyway).

Democracies work only when we engage in the process –– if we speak up, our elected officials will listen. Similar as to how many states have now legalized the use of cannabis due to activism by the electorate, we can petition our State Lead Agencies to allow us to use generic oxalic, formic, and thymol in our hives.

Practical application: It would greatly help if the EPA would clarify to our State Lead Agencies that they have determined that oxalic, formic, and thymol pose no unreasonable risk to the environment when applied in beehives, and thus could be exempted from regulation by the states.

EPA is understandably uncomfortable with setting a precedent of giving beekeepers a free pass, so the most straightforward solution would be for our national organizations to petition the Agency to add oxalic acid, formic acid, thymol, and food-grade plant essential oils to their Minimal Risk Pesticide list, specifically limited to application in beehives. The key point being that this would not open the door for unrestricted use of other pesticides by other ag groups, since it would limit such Minimal Risk use to a specific application (similar to limiting the use of a rat poison to application within bait stations).

Companies may at any time petition the Agency to add or remove an ingredient from the [Minimum Risk] active or inert ingredient lists under the Administrative Procedure Act, even in the absence of guidance [[6]].

If we could convince the EPA to individually add the pesticides thymol, oxalic,  formic, and food-grade plant oils to the Minimal Risk list, that would open the door for individuals or companies to quickly develop and market inexpensive and efficacious treatments for varroa (and possibly Tropilaelaps if it shows up).

“Generally, we do not review products that claim to meet the criteria set by 40 CFR 152.25(f) for exemption from pesticide regulation for companies planning to market such a product. We also do not provide a label review of such products. The producer is responsible to carefully read the criteria and make an evaluation of how the product meets (or does not meet) the criteria” [[7]].

For example, take a look at how my restrictive state of California exempts from registration such substances as thyme oil, eugenol, or citric acid (Figure 3).

Fig. 3 California’s flow chart to determine exemption from regulation [[8]]. Thyme oil (which can contain up to 80% thymol [[9]]) is already on the list. And why couldn’t formic acid be added to the List if sold with a precautionary label to warn the applicator to wear protective equipment?

If the EPA is not willing to add oxalic, etc., to the List, another option at the federal level would be for the beekeepers to ask their Senators and Representatives to introduce legislation in the upcoming Farm Bill –– specifically an amendment to FIRA to exempt oxalic, formic, thymol, and food-grade plant oils from regulation when applied to beehives.

Practical application: Varroa is continuing to develop resistance to amitraz, and the EPA has been ramping up its enforcement actions against unapproved pesticide imports. Complaining and wishing is not going to cut it –– it’s time for a Plan B! Our industry is going to need to progress to more sustainable ways to deal with varroa –– by shifting to biopesticides and eventually mite-resistant stock. It would be great for beekeepers to be able to do this while being compliant with the law. Clear and unconfusing exemptions for our use of off-the-shelf oxalic, formic, and thymol would really help!

Citations

[1] The Status of Our Industry Regarding Varroa Management Part 3, Reading the Fine Print. ABJ, December 2023.

[2] Welcome to the 4th Agricultural Revolution! ABJ, February 2024.

[3] https://www.justice.gov/usao-edca/pr/stockton-beekeeper-charged-conspiring-receive-and-sell-smuggled-illegal-pesticides

[4] California demands an egregiously-high annual $1500 fee to register a pesticide for sale in the State. The manufacturers choke on that cost (pers comm), and I’ve written our Administrator to beg for help.

[5] What the Bleep Are We Doing?

[6] https://www.epa.gov/minimum-risk-pesticides/minimum-risk-addition-inert-ingredient-or-active-ingredient-exemption

[7] https://www.epa.gov/minimum-risk-pesticides/minimum-risk-pesticide-definition-and-product-confirmation#confirm

[8] https://www.cdpr.ca.gov/docs/registration/sec25/minimum_risk_flowchart.pdf

[9] https://ecommons.cornell.edu/server/api/core/bitstreams/61b06502-19f8-442d-af7e-32377f86608b/content

A Field Trial of Probiotics: Part 2

Contents

Introduction. 1

My Two Field Trials 2

Trial #1. 3

Results of Field Trial #1. 4

Analysis of the Effect of Probiotics Upon the Gut Microbiomes. 5

Conclusion of Trial #1. 7

Trial #2. 7

Experimental Setup. 7

Results of Trial #2. 10

Discussion. 12

Final Thoughts 13

Acknowledgements. 13

Citations and Notes 13

A Field Trial of Probiotics

Part 2

First Published in ABJ May 2024

Randy Oliver

ScientificBeekeeping.com

Back in 2020, probiotics for honey bees were all the rage, and beekeepers were spending a ton of money on them. I received a lot of questions as to whether feeding of the products currently on the market was worth the cost. Intrigued, I ran two field trials to give them a fair test. I’ve already written about the practical results of my first trial, but Covid shut down the USDA lab that was about to run the genetic analyses necessary to determine the effects of the probiotics upon the gut microbiomes of the treated bees. I can now share the results –– better late than never!

Introduction

The honey bee gut provides a nutrient-rich environment that is dynamically exploited by various bacteria and fungi. However, all races of Apis mellifera worldwide share a consistent “core” gut microbial community consisting of eight groups of endosymbiotic bacteria [[1]] (plus a large number of other “cryptic” opportunistic bacteria that occur sporadically or at low numbers). It is not yet completely clear as to which of the core bacteria are merely commensals (not actually benefitting the bee), or beneficial mutualists (helping to fight pathogens, assisting in digestion, or producing critical nutrients or other substances), but at least one can be an opportunistic parasitic pathogen [[2]].

There have been a few studies indicating that the feeding of specific strains of the “native” core bacteria as probiotics can be of benefit to the bee [[3]]. However, most commercially-available products consist of bacteria and fungi “foreign” to the honey bee –– species commonly found in mammal guts (easily obtained from one’s own feces) or the soil, and (perhaps most importantly) amenable to mass culture (Figure 1).

Fig. 1 A photograph of the ingredients of one of the tested “direct fed microbials” (DFMs). None of the listed species are native to honey bee guts, the hive, or the floral environment (with the possible exception of Enterococcus faecium).

The question then is whether such bacteria can actually function as probiotics –– generally defined as “live microorganisms that, when administered in adequate amounts, confer a health benefit to the host.” Some beekeepers, upon hearing extravagant claims and gushing testimonials, hope that feeding of these foreign bacteria will confer health or vitality benefits to their colonies.

Or they may do it for another reason. Wikipedia defines probiotics as “live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota.” Based upon this supposition, some beekeepers feed probiotics following their applications of antibiotics used to control AFB or EFB, in the hope that the probiotic will restore the gut microbiome.

There is also the possibility that the introduced organisms might function as prebiotics –– “ingredients that beneficially affect the host by selectively stimulating the growth or activity of the beneficial bacteria in the gut.”

Practical application: A recent review summarizes it nicely –– “There is substantial evidence from in-vitro laboratory studies that suggest beneficial microbes could be an effective method for improving disease resistance in honey bees. However, colony level evidence is lacking and there is urgent need for further validation via controlled field trials” [[4]] (emphasis mine).

It just so happens that controlled field trials are something that I do …

My Two Field Trials

At the trade shows of beekeeping conventions, I make a point of asking the sellers of products promoted to improve bee health or performance, for any hard data that they have to support their claims (I usually get an eyes-down shake of the head). At the suggestion of one of the manufacturers of the two probiotics in Figure 2 that I run a trial myself, I undertook two connected large-scale experiments to see whether the feeding of either probiotic would confer measurable benefit to colonies during our stressful dry summer and pollen-deficient autumn in the California foothills (since I assumed those conditions would give the products the best chance to prove themselves).

In these trials my aim was to impartially and open-mindedly provide these probiotics every opportunity to support the claims that I’d heard for them –– either by their salespersons or expectations by beekeepers themselves. So I blinded both myself, my helpers, and my collaborators at the USDA lab as to which treatments were which, by having an uninvolved visiting researcher place the two probiotics and a powdered sugar control into three bottles labeled A, B and C. We did not unblind ourselves until our analyses of the data were completed.

Trial #1

For this trial I used 78 hives, divided between two separate apiaries (for replication of the experiment), and then in each apiary randomly subdivided them into three test groups, to two of which we applied one of the commercial probiotics (Figure 2), with the third serving as a Control group, to which we applied a sham treatment of powdered sugar alone.

Fig. 2 The two commercial DFM probiotics tested. They both make testable claims, including “for gut health and digestive well-being,” “this is a naturally occurring bacteria that is found in the gastrointestinal tract (GIT) of healthy animals,” “healthy honeybees naturally have these bacteria in their GIT,” and “restores bees’ healthy bacteria, revitalizing their immunity.” My question was whether these beguiling claims would be supported by evidence.

So per label instructions, we applied monthly applications of the probiotics, over the course of four months spanning from the end of our honey flow through (intentionally) our stressful summer dearth period, during which we equally fed pollen subs (Healthy Bee, followed by Mann Lake Bulk Soft) and 1:1 sugar syrup to supplement the minimal natural pollen and nectar flows. By the end of the trial, the colonies had largely filled their upper brood chambers with honey, honeydew, and sugar syrup “honey.”

I’ve previously presented my preliminary results and added additional histograms at my website [[5]], but will here visualize the results in a different manner, and can now include the results of metagenomic analysis.

Note on experimental design: For this trial I chose to use colony strength and weight gain as the metrics to evaluate economic benefit, since these are the two outcomes that put money into my wallet.

Results of Field Trial #1

I can now say that Group C was the Control group given a sham treatment of powdered sugar rather than probiotic. I see no need for me to identify which probiotic was which. Allow me to first present the colony strength and weight results visually in Figures 3 & 4.

Fig. 3 I found (in my opinion) that the best way to visually present the results was to sort the changes in colony strengths from smallest to largest, in order to compare the test groups, combining the data from both experimental yards. Most clusters graded smaller in December than in July (despite the supplemental feeding and considerable weight gain, but that was also likely an artifact of it being cooler when we graded them). The only consistent difference was that Control group C appears to have generally retained or gained more strength than did the probiotic-treated colonies (as evidenced by the shorter blue columns of the colonies that lost strength, and the taller blue columns for those that grew).

Fig. 4 Similar to colony strength, there was no consistent difference in colony weight gain, with the Controls again exhibiting consistently better performance (as evidenced by the taller blue columns).

For the statistical geeks, Table 1 shows the averages numerically.

Table 1 There was no appreciable difference in either change in colony strength or pounds gained between the test groups. If anything, the probiotic-treated colonies overall appeared to slightly underperform relative to the group C controls.

Analysis of the Effect of Probiotics Upon the Gut Microbiomes

Since I wanted to give the probiotics every chance to prove themselves, I collaborated with Dr. Kirk Anderson of the ARS Tucson Lab to perform high-throughput sequencing of 16S rRNA bacterial genes to determine the microbiome structure of individual hindguts taken at the start and end points of this trial, in order to compare the gut microbiomes of the probiotic-treated vs. the untreated Control colonies (Figure 5).

Fig. 5 We collected samples of ~50 bees from every hive at each time point, immediately packed them in dry ice, and then shipped them overnight (at considerable cost) to the Anderson Lab for metagenomic analysis, in order to quantify the prevalence of every strain of bacteria in their guts.

Results of the Metagenomic Analysis

I waited to write this article until our results had been published in an open-access peer-reviewed paper [[6]], with the finding that the microbiota of colonies treated with either probiotic for four months did not differ from those of the Control colonies, and that there was only a scattered and sparse presence of microbes that might have come from the probiotics [[7]].

Conclusions from Trial #1

Under the conditions of this trial, we unfortunately found (1) no benefit from long-term feeding of either probiotic upon colony strength or weight gain, (2) nor upon the composition of the bees’ gut microbiomes, (3) nor did the microbes introduced by the probiotics establish a presence in the bees.

Practical application: Many beekeepers and pollen sub manufacturers add these off-the-shelf probiotics to their hives or products, based solely upon glowing testimonials, rather than any clear supportive hard data that they are actually of benefit (much less worth the cost).

But to be fair, there could conceivably have been two more subtle benefits, so I used the remaining healthy-appearing colonies for a follow-up trial.

Trial #2

The failure of the probiotics to improve colony performance didn’t necessarily mean that they couldn’t confer other benefits. So we reused the probiotic-treated colonies to continue with a second experiment related to how the feeding of probiotics might affect the recovery of the bees’ gut microbiomes after treatment with antibiotics, with the aim of determining:

1. To what extent treatment with either oxytetracycline or tylosin disrupts the gut microbiome.
2. How long it takes for the gut microbiome to “recover” after treatment with antibiotics.
3. Whether the feeding of a probiotic helps to reconstitute the core gut microbiome.
4. Whether the feeding of a probiotic will suppress the prevalence of pathogens in the recovering antibiotic-stressed bees (fungal load, EFB, nosema, or the troublesome viruses deformed wing virus, black queen cell virus, and chronic bee paralysis virus).

Experimental metrics: Since the objectives of this experiment all related to invisible microorganisms in the bees’ bodies, and since we already had baseline data on the bees’ gut community structure, I sent additional samples of bees taken at specific time points to the Anderson Lab for quantitative PCR and (expensive) high-throughput metagenomic sequencing.

Experimental Setup

To set up this experiment, I unblinded myself as to which was the Control group (which we had not treated with probiotics). We then removed any weak colonies remaining from Trial 1, and divided the remainder into seven test groups (Figure 6).

Fig. 6 I kept the probiotic treatments consistent for each hive for the entire course of the two experiments, and randomly assigned antibiotic treatments to each of the three probiotic test groups, in order to be able to tease out every combination of effect due to probiotic and antibiotic.

We had already taken baseline bee samples on December 2 (Time point 0), so began the three antibiotic applications at 4-day intervals on Dec. 7 — similar to how many beekeepers apply antibiotics going into winter (Figure 7).

Fig. 7 We applied the three antibiotic treatments of either oxytetracycline or tylosin at 4-day intervals, sprinkling the label doses of 200 mg a.i. (active ingredient) over the top bars and bees between the two brood chambers.

We then took bee samples at:

Time Point 1: Three days after the third antibiotic application, under the assumption that at that point the antibiotics would have had their maximum effect upon the gut bacteria. Two days later (assuming that the antibiotics would have degraded by then) we then fed each hive a patty consisting of natural pollen and sugar to provide a gut substrate for bacterial growth, and applied the same probiotic that they had been treated with during the summer.

Time Point 2: One week after feeding the probiotics.

Time Point 3: Three weeks after feeding the probiotic, to determine how well the probiotic-treated bees had reestablished their gut microbiome communities compared to the Control bees (Figure 8).

Fig. 8 Timeline of antibiotic treatments (red), feeding of probiotics (green), and the taking of bee samples at four timepoints (yellow).

The weather was unexpectedly warm during the course of the experiment (Figure 9), so the colonies were able to bring in a bit of natural pollen –– perfect conditions to determine the effect of the probiotics.

Fig. 9 I intentionally ran this experiment during the early winter, when the treated workers would be expected to have extended longevity, so that we could track the long-term impact of antibiotic treatment and subsequent recovery of the bees’ gut microbiomes. As it turned out, we enjoyed an extended autumn that year, and the colonies did not go completely broodless during the course of the trial (so at least some the bees sampled at Time Point 3 may have emerged after the application of the antibiotics). Weather chart courtesy personal weather station KCAGRASS50.

The Anderson Lab sequenced the genetics of the gut microbiota from 240 individual bees, taken from 60 hives belonging to the seven treatment groups, identifying 229 “types” of bacteria (operational taxonomic units or OTUs), as well as performing quantitative PCR to identify pathogens. Their informative huge raw data set is readily available at [[8]].

Results of Trial #2

Let’s start with our finding that treatment with antibiotics caused long-term dysbiosis of the gut microbial communities of non-probiotic-treated bees, treated with either oxytet or tylosin, relative to untreated bees (Figure 10, snipped from our published paper).

Fig. 10 Note how consistent, over time, the gut microbiome was in bees from the untreated Control hives, compared to the disruption and poor recovery of the microbiome communities in antibiotic-treated bees. Not shown above is that much (or nearly all in some cases) of the gut microbiome was reduced in all groups at the 7-day time point –– presumably due to cross-colony transfer of the antibiotics.

It’s pretty clear that treatment with antibiotics greatly disrupts the universal gut microbiome that Apis mellifera has coevolved with over millions of years. But what many beekeepers are interested in is whether one can mitigate that adverse effect by feeding a probiotic to help the bees to recover and reestablish a healthy gut microbiome. The Anderson Lab’s analysis statistically concluded that feeding probiotics didn’t make a difference, but I wanted to confirm that visually for the benefit of my readers. So I processed their huge data set to create a chart comparing the gut community structures of individual bees taken from different hives in each test group, arranged in before-and-after matching pairs of charts (Figure 11):

Fig. 11 To produce the above charts, I combined the subspecies of the eight core bacterial groups, and combined the rest of the 221 recorded “cryptic” OTUs under “Unclassified.” The lefthand columns of each pair of charts represent bees sampled before antibiotic treatment (all colonies received treatment with antibiotic); the righthand columns represent the microbiomes 21 days after the feeding of a “recovery” probiotic (none were given to the Controls).

Note that the gut microbiomes of bees sampled prior to treatment with antibiotics were fairly similar in the left-hand columns of all test groups. The feeding of either probiotic did not appear to improve the reestablishment of their core gut microbiome community structures in the right-hand columns, since the “recovered” structures were still out of balance in all groups, whether having received a probiotic or not [[9]]. Also note the relatively small proportion of unclassified bacteria (whether from the probiotics or elsewhere) present in most of the bees.

In summary, the Anderson Lab found that:                                                                                    

• Consistent with other findings [[10]], application of the antibiotics oxytet or tylosin strongly decreased (or sometimes nearly eliminated) the gut microbial community in treated bees [[11]], and caused a persistent dysbiotic effect on the community structure of the hindgut microbiome lasting at least three weeks.
• They could not detect any measurable benefit from the feeding of the tested probiotics upon the reestablishment of the bees’ gut microbiomes [[12]].
• They could not detect any correlation between feeding of a probiotic and the abundance or prevalence of the seven common pathogens they tested for [[13]].

Discussion

As much as I would have liked to have confirmed the claimed benefits for the two DFM (direct-fed microbial) probiotics that I tested, our data did not provide any supportive evidence for those claims ––as far as improvement in colony strength or performance, or via genetic analysis of their effect upon the endosymbiont microbiomes, or pathogens in the bees’ bodies.

Practical application: Many beekeepers spend money on probiotics as an “insurance policy,” or in the expectation that they will in some way “make their colonies healthier,” “improve their performance,” or “suppress pathogens.” This might well have been the case had the DFMs contained beneficial “native” strains of bacteria able to establish in the bees’ guts, but that didn’t occur with the products tested.

Aside from that, one finding of great interest is our confirmation of the very negative impact of our commonly-used antibiotics on the normally well-established beneficial endosymbiotic “core” microbiome in healthy bees. In general, either antibiotic treatment was hard on the gut bacteria, disrupted the established community structure, and generated an environment ripe for exploitation by “outside” bacteria, or strains of the core species exhibiting resistance to those antibiotics.

Practical application: A number of beekeepers are under the impression that “it’s good idea” to feed a probiotic after antibiotic treatments, hoping that it will help their bees’ “normal” gut microbiomes to recover. This brings us to …

A needed disclaimer: As one of the manufacturers themselves recently clarified, probiotics consisting of “foreign” microbes are not intended to help in the reestablishment of the gut microbiome, since those microbes would not be expected to “take up residence,” nor evoke any detectable change in the microbes that are normally present. I personally feel that it behooves the sellers of honey bee probiotics to make this clear on their label!

A Bright Future?

This doesn’t mean that a “recovery” probiotic couldn’t be developed. A recent paper presented “new experimental results showing that non-native bacterial strains from a commercial probiotic product fail to establish in the worker bee gut, but a mixture of native gut bacterial strains colonizes robustly and resembles a natural microbiota in eliciting expression of bee genes related to immunity and metabolism. Though some questions are unanswered, the future of probiotics for honeybees is bright. It may be possible to design specific communities of natural gut isolates that stably replenish gut communities disrupted by the many stressors bees face and that are economical and efficient for use in apiaries” [[14]].

Final thoughts

It’s conceivable that we may find or develop strains of bacteria that could be introduced to colonies to fight disease, help the bees to digest certain foods, or to produce essential nutrients or other beneficial substances. But keep in mind that honey bees, over the millennia, have already been exposed to virtually every species of bacteria on this planet, and evolutionary pressure is continually selecting for strain-specific core microbiomes “that work well together,” not just in a few labs, but in at least four trillion individual honey bees every day!

Not only that, but every bee gets naturally inoculated with those endosymbionts within hours of emerging from its pupa, so generally would need no help from a beekeeper. So the “proof of benefit” is really up to those selling a product. I ran these experiments as an example of the sort of hard data that we beekeepers would like to see, so that we can make informed decisions as to how we spend our money.

The results of this particular study are for a single trial in the California foothills (objective, impartial, blinded, and replicated). However, similar results have been found by other research groups (pers comm), including one [[15]], that noted: “Probiotics, in theory and concept, are a promising solution to enhance bee health, but the current market available products for beekeepers are making claims that far outreach the ability of their products.”

Acknowledgements

Metagenomic analysis is not cheap, so I see why there are not a lot of hard data on this subject –– it cost me more than $8000 for the collection, shipping, and processing of the samples. And that’s not counting the extensive amount of time involved in lab work and the tedious analysis of the data performed by Dr. Kirk Anderson’s group. So I thank the ARS crew, as well as all you beekeepers who have donated to support our research!

Citations and Notes

[1] Bobay, L, et al. (2020) Strain structure and dynamics revealed by targeted deep sequencing of the honey bee gut microbiome. Msphere 5(4): 10-1128.

From the above paper: “The fact that bees from different hives and states present similar strain profiles, whereas many bees from the same hive have completely different strain compositions, suggests that there are complex strain dynamics in the honey bee microbiota.”

The players involved in the “core” microbiome appear to be in continual dynamics, and new metagenomic analyses suggest that the taxonomy is open to revision, with some currently-named “species” exhibiting unique strains and perhaps continually mutating and evolving.

[2] Engel, P, et al (2015). The bacterium Frischella perrara causes scab formation in the gut of its honeybee host. MBio, 6(3): 10-1128.

[3] Patruica, S & I Hutu (2013) Economic benefits of using prebiotic and probiotic products as supplements in stimulation feeds administered to bee colonies. Turkish Journal of Veterinary & Animal Sciences 37(3): 259-263.

Borges, D, et al (2021). Effects of prebiotics and probiotics on honey bees (Apis mellifera) infected with the microsporidian parasite Nosema ceranae. Microorganisms 9(3): 481.

Daisley, B, et al (2020) Novel probiotic approach to counter Paenibacillus larvae infection in honey bees. The ISME journal 14(2): 476-491.

[4] Rodríguez, M, et al (2023) Probiotics and in-hive fermentation as a source of beneficial microbes to support the gut microbial health of honey bees. Journal of Insect Science 23(6): 19.

[5] Oliver, R (2021) A Field Trial of Probiotics American Bee Journal May 2021 https://scientificbeekeeping.com/a-field-trial-of-probiotics/

[6] Anderson, K. E., Allen, N. O., Copeland, D. C., Kortenkamp, O. L., Erickson, R., Mott, B. M., & Oliver, R. (2024) A longitudinal field study of commercial honey bees shows that non-native probiotics do not rescue antibiotic treatment, and are generally not beneficial. Scientific Reports 14(1): 1954. https://www.nature.com/articles/s41598-024-52118-z

[7] Supplementary Figure 1 https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-024-52118-z/MediaObjects/41598_2024_52118_MOESM1_ESM.tif

Supplementary Table 4 https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-024-52118-z/MediaObjects/41598_2024_52118_MOESM5_ESM.xlsx

[8] The raw data is in Supplementary Table 3. See below.

[9] If you’re interested in diving deeper, I’d be happy to share my spreadsheet to show you how to easily do it.

[10] Daisley, B, et al (2020) Lactobacillus spp. attenuate antibiotic-induced immune and microbiota dysregulation in honey bees. Communications Biology 3(1): 534 https://www.nature.com/articles/s42003-020-01259-8

Powell, J, et al. (2021) Field-realistic tylosin exposure impacts honey bee microbiota and pathogen susceptibility, which is ameliorated by native gut probiotics. Microbiology Spectrum 9(1): 10-1128. https://journals.asm.org/doi/pdf/10.1128/spectrum.00103-21

[11] Supplementary Table 3 https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-024-52118-z/MediaObjects/41598_2024_52118_MOESM4_ESM.xlsx

[12] Supplementary Table 5 https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-024-52118-z/MediaObjects/41598_2024_52118_MOESM6_ESM.xlsx

[13] Supplementary Table 2 https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-024-52118-z/MediaObjects/41598_2024_52118_MOESM3_ESM.xlsx

[14] Motta, E, et al (2022) Prospects for probiotics in social bees. Philosophical Transactions of the Royal Society B 377(1853): 20210156.

[15] Damico, M, et al (2023) Testing the effectiveness of a commercially sold probiotic on restoring the gut microbiota of honey bees: A field study. Probiotics and Antimicrobial Proteins 1-10. https://www.biorxiv.org/content/10.1101/2023.09.13.557574v2.full

Extended Release Thymol Blocks

Contents

My Preliminary Findings 1

Preparation. 2

Application. 4

Colony Response to the Treatment 6

Final Inspection. 13

Effect Upon Varroa. 15

Is it Worth Preparing Your Own?. 15

Remaining Questions to Answer 15

There’s a Reason that EPA Registers Miticides! 16

Citations and Notes 16

Extended-Release Thymol Blocks

Randy Oliver

ScientificBeekeeping.com

First published in ABJ April 2024

Since varroa mites spend roughly 70% of their time under the cappings, miticides are most efficacious if applied in an extended-release formulation —which exposes the mites to the treatment while they are in their dispersal phase.  With regard to thymol, slow release is achieved by dissolving it in oil, or embedding it in absorbent strips or aqueous gel.  But all the currently-registered thymol products release their vapors fairly quickly, and thus require repeated applications.

In 2022 I published the results of my experimentation (under permit) of a novel way of applying this biopesticide [[1]].  Since the EPA has now stated that it does not restrict “own use” of generic thymol, we beekeepers may be able convince our State Lead Agencies to follow suit and allow us to use this method.

My Preliminary Findings

I had previously determined colony tolerance of slow-release thymol, as well as a dose/response curve  (Figure 1).

Fig. 1. My preliminary research suggested that the optimal dose of thymol to apply by this method would be around 40 grams –– less in total than the amount allowed by the label of Apiguard (up to four weekly applications of 12.5 grams).  So that’s what I tested last summer.

Preparation

I had originally experimented with Homasote fiberboard (made from recycled newspaper [[2]]), but had trouble finding it in California, so also tested an available acoustic soundboard made from wood fiber [[3]].  I dissolved USP-grade thymol [[4]] in denatured alcohol at the ratio of 1 gram of thymol crystals to 1 mL of alcohol (the thymol dissolves quickly if the alcohol is slightly warmed and stirred).  This creates a nearly-saturated solution that contains ~0.6 grams of thymol per milliliter of solution.

Method

Let’s say that you wanted to treat five hives, so you’d need 4 blocks per hive x 5 hives = 20 blocks in total.

Step 1: Use a table saw to cut twenty 1” x 4” blocks from ½”-thick wood soundboard (1” x 4¾” for Homasote) and place them upright on end, side-by-side in a container.  Important note: these dimensions are for thymol dissolved in denatured alcohol as above (see the note below).

Step 2: Then mix up your thymol solution to match the number of blocks.  For 20 blocks, each to hold 10 g of thymol (40 g per hive), dissolve 20 x 10 g = 200 g of thymol crystals into an equal number of milliliters (200 mL) of alcohol.

Step 3: Pour the solution into the container so that the blocks evenly absorb it (Figure 2).

Fig. 2 Because you made the blocks longer than necessary for full absorption, they will completely suck up all the solution.  Since you know how much total thymol you added, you then know how much thymol (on average) each block absorbed.  Simple!

Note:  I used denatured alcohol (ethanol typically with 10% methanol).  Because ethanol is naturally produced during the fermentation of beebread (and since bees like ethanol), and since I allowed the alcohol to evaporate off prior to placing the blocks into hives, I wasn’t concerned about contamination of my combs. However, ethanol is not on the Minimal Risk Inerts list, so while writing this article, I purchased some 99.9% isopropyl alcohol (which is on the List), assuming that it would dissolve thymol similarly to denatured alcohol.  Once again, so much for assumptions!

I pulled out the scale and graduated cylinders, and went to the lab (my kitchen) to compare the two:

Saturated solutions (updated)

I’ve tried at least two brands of denatured alcohol and one brand of 99.9% isopropyl alcohol.  Each appeared to have a different ability to dissolve thymol!

In general, 1000 grams of thymol to 1000 mL of denatured alcohol makes ~2070 mL of nearly-saturated solution.

So ~21 mL solution/10g of thymol

Difference if you’re using 99.9% isopropyl alcohol:  thymol does not appear to be as soluble in isopropyl alcohol as it is in ethanol or methanol!  In my single test, 50 g thymol + 100 mL 99.9% isopropyl alcohol (heated)  = 128 mL slightly supersaturated solution.  If you use isopropyl, you’ll need to cut your blocks at least 50% longer.

BASIC RECIPE FOR DENATURED ALCOHOL

Once the blocks have absorbed the solution, spread them out and allow the alcohol to flash off. For quick evaporation, spread out the blocks in a single layer over a screen –– in the sun or a warm ventilated place.  It often takes less than an hour for the alcohol to evaporate off.

Apply 2 – 4 blocks per hive, dependent upon the ambient temperature, and where placed (between the brood chambers or in a rim on top).

A tip:  If you write down the starting weight of a block before absorption, you can reweigh them as the alcohol evaporates, until the blocks weigh only slightly over 10 grams more than they started at (due to the added weight of the thymol) –– it’s not necessary to completely evaporate the alcohol.

A common misconception:  It’s a common misconception that thymol is highly volatile.  It isn’t!  At 77°F (25°C), the vapor pressure of thymol is only 0.016 mm of mercury, whereas the vapor pressure of ethanol is 59 mm Hg).  Virtually all the alcohol will evaporate off before a measurable amount of thymol does!  Once most of the alcohol has evaporated, the blocks can be stored in a sealed plastic bag or other airtight container (Figure 3).

Fig. 3 The blocks (Homasote on the left, wood soundboard to the right) are here packed for storage after drying.

Application to The Hives

We started the field trial near the end of July, in hot, dry weather (Figure 4).

Fig. 4 In the California foothills, our honey flow is generally over by the end of July, providing us a window of opportunity to eliminate varroa before we start feeding pollen sub to stimulate brood rearing in mid-September.  I wanted to see how a single application of thymol blocks compared to the two rounds of Apiguard that we’ve used in the past (which really disrupted brood rearing in hot weather).

Unfortunately, due to my sons’ successful mite management to date, we needed to perform a lot of mite washes to find enough hives (34) with mite counts high enough to use for the trial (so the experiment was divided between five different yards, providing replication).  All the test colonies were in double deeps, generally with brood in both boxes.  We used a randomized block design, blocking by the starting mite counts for each yard, to randomly assign whether a colony would receive Homasote or wood fiber blocks.  Four colonies had excessively high mite counts, so I applied blocks containing a total of 48 grams of thymol to them to see how they’d handle the higher dose.

We used a 1½-inch rim atop each hive, and placed four thymol blocks in the corners (Figure 5).

Fig. 5 We replaced our dark plywood migratory covers over the rims.  Midday temperatures of the tops of the covers reached 160°F (120°F on the undersides), so the thymol received plenty of heat to drive evaporation.

Colony Response to the Treatment

During the 21 days of treatment (slightly over one full bee brood cycle [[5]]), we inspected the hives regularly.  There was considerable variation in how each colony reacted to the treatment (Figures 6-12).

Fig. 6 Most colonies ceased rearing young brood in the upper chamber, but continued unabated below.

Fig. 7 And then they started storing nectar from the light flow (or from jars of syrup in some yards) in the former brood cells (you can just catch the glisten in this photo).  I liked this, since we want the box above the cluster to be filled with honey (natural or from syrup), prior to winter.

Fig. 8 In many of the hives, the queen ignored the fumes and filled empty cells in the upper chamber with eggs, but we often saw them not progress to the larval stage (we couldn’t tell whether the eggs died, or the nurses cannibalized them).

Fig. 9 Not to be outdone, a couple of colonies completely ignored the fumes, built fresh comb in the rim, and continually reared brood right up to the blocks!

Fig. 10 The bees generally left the thymol blocks alone, only building propolis “shells” around a few.  Only after three weeks did any begin chewing them.

Fig. 11 Our most surprising observation was that every colony maintained continual brood rearing during the 21-day treatment — most of them mainly in the lower box.

Fig. 12 Unlike as with Apiguard –– the particles of which the bees carry down through the brood area, greatly disrupting brood rearing –– there was always plenty of brood of all ages in every hive at every inspection.

We ended the trial after 21 days, by which time the thymol had largely evaporated from the blocks, and most colonies had begun brood rearing in the upper chamber again (Figure 13).

Final Inspection

Fig. 13 Corrine Jones helped me with final inspections.  The sealed brood in this frame is at least 12 days old — indicating that the nurses were accepting and feeding larvae in the upper box halfway through the treatment.  We were surprised by the amount of brood rearing that took place during the hot, dry August pollen dearth (compared to our long experience with Apiguard).

We didn’t observe any queen losses or other notable adverse effects upon the colonies.

Effect Upon Varroa

The colonies fared surprisingly well; I can’t say the same for the unfortunate mites (Figure 14).

Fig. 14 It didn’t take long to count the mites in the final mite washes! We counted 851 at the start, and only 14 at the end –– a 98% reduction.  The results were consistent from yard to yard (not shown).

Practical application:  This is one of the most efficacious [[6]] treatments I’ve ever seen for colonies with brood, and it only took a single application and three weeks duration, leaving the colonies robust and thriving.

I tracked the colonies for the rest of the season.  There was no bounce-back of mites, and the colonies went into winter in great condition.

Is it Worth Preparing Your Own?

There is a labor saving from being able to only apply a single application for a three-week treatment with few adverse effects, but it takes some time and effort to prepare the blocks.  Here’s a breakdown of estimated costs (not including shipping), using prices from the internet and Wintersun Chemical (a large commercial supplier of USP-grade industrial chemicals that we find easy to work with)(Table 2).

Table 2.  Unfortunately, off-the-shelf thymol is expensive in small quantities. The cost of the soundboard is negligible in quantity, so I didn’t include it, nor did I include any shipping costs.

A Remaining Question

I wondered what difference it would make if I applied the treatment later in the season, in cooler weather, while we were trying to grow weak colonies by feeding syrup and sub in late September?

So I waited until the weather cooled, and treated two very weak colonies with moderate mite counts, located in the shade.  They took syrup and pollen sub eagerly during treatment, but they didn’t grow much (but no colonies were growing much at that time).  The degree of mite reduction wasn’t great.  The thymol blocks (likely at a lower dose) may need to be placed between the brood chambers in cooler weather.

Practical application:  These blocks can indeed be placed between the brood chambers, but I have only preliminary observations from a few test colonies, and only during the summer. They appeared to tolerate up to 36 grams of thymol well.  Please let me know your results if you try different placements, time of year, or application methods!

There’s a Reason that EPA Registers Miticides!

An adverse effect report:  I just heard today from a southeastern beekeeper who applied 36 grams of thymol to singles in warm springtime weather, and observed some queen kills –– likely due to that being too strong a dose for singles.

In the registration process of any miticide, the EPA pays great attention to the formulation and the label, to ensure that application of a registered miticide by the end user does not pose an unreasonable risk to the public, the environment, the bee colony itself, or to the applicator (you).  Keep in mind that plants create oxalic acid, formic acid, thymol, and essential oils as poisons — you can’t just go about applying them willy-nilly.

Practical application: Thymol applied at too high a rate of release, relative to temperature, hive size, and colony strength, can kill bees and brood — details are important!  My test was on double deeps, and with the 40-gram dose in a rim on top.  If your state allows use of unregistered miticides, follow tested methods of application, or experiment very carefully on only a few hives.

Citations and Notes

[1] Thymol — A new application method? Part 2.  American Bee Journal December 2022  https://scientificbeekeeping.com/thymol-a-new-application-method-part-2/

[2] Homasote 440 Medium Density Fiber Board; (94-98% paper cellulose, 1-6% paraffin wax, <0.1%  copper metaborate (Homasote was approved by EPA for the Miteaway II pads).

[3] ½-inch Sound deadening panel, Building Products of Canada Corp.  “produced from non-toxic organic material and natural wood fibres that are wax impregnated.”

[4] From Wintersun Chemical www.wintersunchem.com

[5] A bee brood cycle averages ~20 days in hot weather), whereas a varroa reproductive cycle is typically around 17 days during active broodrearing.

[6] Technically I couldn’t calculate efficacy, since I didn’t run a control group.

The Elephant and the EPA

The Elephant and the EPA

Randy Oliver

ScientificBeekeeping.com

First published in ABJ April 2024

A related pair of issues are coming to a head: (1) The “elephant in the room” that nobody wants to talk about –– that the EPA is feeling increasing pressure to ramp up enforcement against beekeeper use of unapproved treatments, and (2) the increasing development by varroa of resistance to the miticide amitraz. These issues are not going to “go away,” and ignoring an issue can turn it into a problem. So what’s our Plan B?

Our Situation is Hardly Unique or Unexpected

Most beekeepers in the world have varroa in their hives, and in countries that have relied on neurotoxic synthetic miticides to control the pest, they’ve found that these silver bullets “work great, until they don’t” [[1]^{, [2]}]. In tropical and Mediterranean countries, where mites enjoy more reproductive cycles per year, beekeepers are complaining that the synthetic miticides are no longer efficacious. Their reports provide a crystal ball for beekeepers in North America — unless a new silver bullet hits the market soon, we’re gonna need to adopt different methods for dealing with the mite. Our most promising fallbacks are the adoption of resistant stocks, and a shift to biopesticides –– notably oxalic and formic acids, thymol, and perhaps other plant essential oils (two things that I have been focusing on for some years).

How Did We Get to Where We Are?

Americans in general, and beekeepers in particular, have always been “do-it-yourselfers.” At a convention, when a researcher names a promising new active ingredient against varroa, I see beekeepers in the audience pulling out their pens. They’ll likely be experimenting with that active ingredient well before someone goes through the EPA’s costly and time-consuming registration process.

Practical result: Beekeepers are an “orphan industry,” without enough buyer demand to make it cost-effective for developers of formulated varroa-control products to go through EPA’s expensive registration process. This has resulted in there being a paucity of registered varroa treatments, all of which are unduly expensive. The EPA is aware of this, and is now fast-tracking registration of biopesticides, as well as a new amitraz product (Figure 1).

Fig. 1 The EPA has recently fast-tracked registration of new formulations of two existing active ingredients. This sort of product competition is good for us, both option-wise and price-wise.

In 1988, shortly after varroa hit our shores, this very journal published an article from Israel [[3]] stating that: “Colonies in Israel infested with V. jacobsoni were treated with Mavrik (a.i. fluvalinate). A small piece of plywood which had been soaked in 20% Mavrik emulsion and then dried was hung between the combs in the centre of the brood nest. … It is concluded that four Mavrik treatments per colony per year can keep V. jacobsoni populations to levels below the economic damage threshold.”

This was a watershed moment for the pesticide-averse beekeeping industry –– for the first time, we became the main source of pesticide contamination of our combs (setting a new baseline for exposure of our bees to pesticides). The “off-label” use (using it for a different pest than those specified on the label) of Mavrik was already well established before Apistan got registered by the EPA in 1990. Since the registered product was far more expensive, and tougher to apply and remove than homemade towels, most large-scale beekeepers stuck with their homebrews.

Anyway, the result of widespread and continual use of fluvalinate in the U.S. followed the same trajectory that occurred in Mediterranean Europe, with mites soon developing widespread resistance to the chemical. By the late 1990s, commercial beekeepers were desperate for something else. The EPA, which was actively phasing out dangerous organophosphate insecticides, registered coumaphos in safe-to-apply Checkmite+ strips in 1999. By this time, commercial beekeepers had earned the moniker of being “pesticide scofflaws,” and since Checkmite+ was more expensive than powdered Co-Ral cattle dip, some started dusting their hives with it –– a foolishly risky thing for an applicator to do! Anyway, within three years mites developed resistance to that silver bullet, and a number of those who had used it off-label had so seriously contaminated their combs that they had to burn them all!

In 2004, ARS researcher Patti Elzen wrote [[4]]: “Given the serious situation of [mite] resistance to both registered compounds [fluvalinate and coumaphos], there is a critical need to develop alternative control strategies.”

By this time thymol had been registered as Apiguard and Apilife VAR, and formic acid in Mite Away pads. After using Apistan for several years, and Checkmite+ once, I decided to step off the synthetic miticide treadmill of watching mites develop resistance to one silver bullet after another, and went through a long learning curve experimenting with formic acid, drone brood removal, thymol, sugar dusting, and oxalic acid to figure out which ones were efficacious (working under a Pesticide Research Authorization when required).

But by that time, most commercial beekeepers had already become thoroughly accustomed to using off-label Taktic (amitraz), which still remained efficacious and simple to apply, so my articles on shifting to biopesticides fell largely upon deaf ears.

Then in 2013 I was approached by the manufacturer of amitraz, who asked me for my opinion on whether it would be worth his while to spend nearly a million dollars for his company to register amitraz in a plastic strip for varroa control. To do so, since EPA had determined that due to amitraz having been recently registered for use in tick collars for dogs, that it had filled its “risk cup” — and to register an additional product, another product would need to be withdrawn from the market — the manufacturer decided to let go of Taktic, and I was given a heads-up that it would be pulled from the market within a year, but that I couldn’t disclose that information.

Have You Got a Plan B?

I feared that my commercial compatriots would be caught off guard, having not yet learned how to use alternative treatments. So at national conventions, I tried to sneak in a heads-up (Figure 2).

Fig. 2 In order not to disclose confidential information, I purchased a can of Taktic (still unused to this day) and had my son Eric pose for the photos, suggesting that the chemical might soon lose efficacy. Once Apivar was brought to market, I warned that “It would be wise for beekeepers to rotate Apivar treatments with other active ingredients to delay the inevitable development of resistance to this product by varroa.” [[5]]

We all knew that it would eventually happen: Repeated applications of a single active ingredient, without rotation with chemicals having different modes of action, engaged our industry in a (successful) selective breeding program for mites resistant to amitraz. It’s just taking a lot longer with amitraz than it did with the previous silver bullets. Amitraz is now requiring so many treatments per year that many commercial beekeepers are finally rotating in other treatments, or completely giving up on the chemical.

The bottom line: Amitraz has been a lifesaver for commercial beekeepers, but it appears that the joyride with this miticide may be nearing an end — not only due to its loss of efficacy, but because of concerns about maintaining the image of “pure” honey, resentment from other beekeepers who are dealing with the greater cost of using registered products, but perhaps most importantly, complaints to the EPA from apiary inspectors who don’t feel right about turning a blind eye toward beekeepers’ scofflaw attitude toward pesticide use. By all means, read the letter sent to the EPA in 2021 by the Association of American Pesticide Control Officials –– which demanded immediate enforcement action to be taken against the use of illegal pesticides by beekeepers [[6]]. This brings us to:

Beekeepers and their Regulators

In some countries (such as in the EU), miticides are regulated by strict veterinary agencies, and beekeepers tend to be compliant with the law. In the U.S., miticides are currently regulated by the EPA as pesticides, but read Charlie Linder’s articles regarding how the FDA is considering taking responsibility (which could have dire consequences for beekeepers).

Worldwide, the synthetic miticides fluvalinate, bifenthrin, coumaphos, and amitraz are widely registered, but there may be fewer or additional options available in any country. Ditto for oxalic, lactic, hops beta, and formic acids, as well as thymol and other essential oils. And approved application methods vary — some agencies feel that beekeepers can’t safely handle liquid formic acid, whereas others allow the burning of paper ribbons of amitraz.

I recently returned from Azerbaijan (Figure 3), where it is the Wild West as far as use of unregulated varroa treatments, with a wide array of formulated products and mixtures of active ingredients being shipped in from surrounding countries.

Fig. 3 A queen production yard in Azerbaijan. The hive bodies are huge and heavy –– containing eleven Dadant deep (12”) frames, with the boxes made of 1½”-thick wood. The beekeepers there are justifiably worried about Tropilaelaps which is already causing havoc in neighboring Russia.

The risk to employees: EPA is not only concerned about amitraz residues in honey and beeswax, but also that beekeepers (and their employees) who mix it up and apply it are at risk of reproductive, developmental, and neurological harm, especially when the emulsifiable concentrate is used.

Heads up: Now that the EPA fast-tracked the registration of a quick-release amitraz treatment (Amiflex) and two oxalic products (Varroxsan and EZ-OX), they may well be gearing up for serious enforcement action. So I’ve been working hard to see whether we can convince the EPA and our state agencies to allow us to use generic oxalic, formic, and thymol.

Anticipating a Problem, and Being Proactive

The above problems have been a long time coming, with many in our industry hiding their heads in the sand, hoping that they’d never have to face them. In my humble opinion, the smart thing to do would be to anticipate that change was imminent, and be ready with a workable solution.

So I myself, along with a few others, proactively first asked the EPA to grant us an exemption (similar to New Zealand’s [[7]]), for our use of the generic, off-the-shelf “natural” chemicals oxalic acid, formic acid, thymol, and food-grade plant essential oils (hereafter referred to as the “Natural Treatments”) for miticidal purposes. When that request was denied, impressed by the diligence of lawyers I’d seen on TV, I dove into FIFRA (the mandate that gives the EPA its authority to regulate pesticides) to look for a Plan B.

Freedom vs. Regulation

Lo and behold, I found a loophole in 7 U.S.C. § 136a(a) of FIFRA: “To the extent necessary to prevent unreasonable adverse effects on the environment, the Administrator may by regulation limit the distribution, sale, or use in any State of any pesticide that is not registered.”

The way that I interpreted that sentence was that that FIFRA gives the EPA the mandate to regulate the production, distribution, sale, and use of any pesticide that poses unreasonable risk to the environment, but not a mandate to restrict the use of those that do not pose such risk.

So I wrote a letter to the Office of Pesticide Programs requesting clarification [[8]]. When I didn’t get a reply, I asked the ABF and AHPA to send it again as cosigners (to which the Agency finally replied). In subsequent virtual meetings, EPA employees confirmed that my interpretation was correct, and that they would work with us to clarify how we could apply the unregistered natural treatments.

To our surprise, what their lawyers instead did was to wrap our request for clarification into their response to the apiary inspectors in their “Advisory on the Applicability FIFRA and FFDCA for Substances used to Control Varroa Mites in Beehives.” [[9]]. The EPA’s lawyers apparently get paid by the word, so they swallowed a dose of Lesfuquithum and produced a nearly 3000-word document. Unfortunately, many beekeepers found it to be unclear in critical specifics.

What Did the Advisory Say?

Nothing much that we didn’t already know –– that there are registered varroacides available for purchase, and that the label is the law. But hidden deep in the Advisory was the answer to our question:

“EPA considers any application of an unregistered pesticide for other than personal use (e.g., application of an unregistered pesticide to another person’s property) to be distribution of an unregistered pesticide and a violation of FIFRA” (emphasis mine).

Practical application: This was a roundabout way of saying that since use of the Natural Treatments poses no unreasonable risk to the environment, that FIFRA does not grant EPA authority to regulate our use (as opposed to the sale or distribution) of them. Their Advisory left a number of questions unclearly answered (Figure 4).

Fig. 4 I consider the Agency’s publication of the convoluted sentence above to be a weak “win,” but it appears that the EPA doesn’t want to give us a straight answer. So I went back through FIFRA, and found that “Under FIRA, the EPA is bound by law to inform and educate pesticide users about accepted uses and other regulations” [[10]].

Letter #2, and My Legal Points

Continuing to play lawyer, I’ve now written a draft for a second letter to send to the EPA, stating, “In this letter we are not in any way challenging the EPA nor the Advisory, but only asking for clarification of details,” reminding them of their duty to inform and educate us regarding “accepted uses.”

I point out that the EPA encourages the use of biopesticides, and that beekeeper adoption of biopesticides would reduce our use of currently-registered “conventional” miticides that unfortunately contaminate our combs and honey, and exhibit greater risk to man and the environment.

Also, as acknowledged in the Advisory, FIFRA does not differentiate between “own use” and “personal use.” This is a key point for which we are asking for more clarification, especially since the Advisory later uses the undefined term “personal” in the statement: “Personal use would not likely include activities that involve any operation in commerce such as selling or distribution of bees/colonies, pollination services, or honey.”

The above argument appears to be created out of whole cloth. FIFRA does not differentiate between “hobbyists” and migratory beekeepers as end users, so we beekeepers are unclear about why the Advisory does so. Nor does the Advisory’s newly-created term “own personal use,” appear in FIFRA, nor has EPA developed any special exceptions to FIFRA regulation for what might be considered “own personal use.” And what’s with their using the word “likely” in the sentence “Personal use would not likely include activities that involve any operation in commerce such as selling or distribution of bees/colonies, pollination services, or honey”?

An Example to Consider

As an example,  akin to oxalic acid, the EPA does not consider common hand soap to present unreasonable risk to man or the environment, and lists it as a minimum risk inert exempt from tolerance, but does not list soap as a minimum risk active ingredient. Therefore, a rancher who uses hand soap with the intent to kill fleas on her goats would be “personally using an unregistered pesticide.” According to the Advisory, if she then rented her goats out for brush control, or sold them, or cheese made from their milk, she would be committing an “operation in commerce” of distributing pesticides and subject to enforcement action under FIFRA. It stretches credulity that the EPA would entertain such enforcement action.

Not only that, but the EPA clearly differentiates between “pesticides” and “treated articles” — the EPA does not restrict the movement, rental, or sale of a beehive treated with registered products, and thus has no justification to restrict such “distribution” of beehives treated with unregistered oxalic, formic, thymol, or food-grade plant oils that pose no risk to the environment. An even stronger example is the EPA’s decision to consider seeds treated with concentrated amounts of neonicotinoids as “treated articles” exempt from regulation of sale or use.

We understand that a beekeeper cannot, under the definitions in FIFRA, distribute or sell an unregistered pesticide to another person for pesticidal purposes. But that definition applies only to the pesticide, not to the sale or transport of a crop that has been treated with a pesticide. As in the aforementioned hypothetical case of the goat rancher, or the case of treated seed, FIFRA would consider beehives treated with a pesticide to be “treated articles,” rather than as pesticides themselves.

Likewise, would a beekeeper (whether “hobby” or “commercial”) who as an “end user” applied unregistered oxalic acid to their hive and then sold or rented that hive in another state for pollination purposes, be guilty of distribution of those pesticides? To my understanding, there would be no restrictions on the transportation, rental, or selling of hives that had been previously treated with purified oxalic acid, formic acid, thymol, or food-grade plant essential oils. We need a clear answer to this question!

The EPA is justifiably concerned about beekeepers inadvertently “adulterating” their honey by using impure active ingredients or unapproved excipients, adjuvants, or delivery matrices (termed in FIFRA as “inerts”).

I point out that to avoid adulterating honey intended for sale, beekeepers who use Natural Treatments must use only those of high purity, and dilute them solely with minimum risk inerts (described as a commonly consumed food commodity, animal feed item, or edible fat and oil as specified in 40 CFR 180.950, or listed as Inert Ingredients Eligible for FIFRA 25(b) Pesticide Products). Such allowed inerts would include water, isopropyl alcohol, glycerin, vegetable oils, mineral oil, cellulose, cardboard, paper, or commonly consumed food commodities (all approved for use on food crops) while colonies were producing honey for sale. When not producing honey for sale, cotton or sawdust could also be used. In addition, although not of concern as a health risk, thymol may affect the odor of honey, and should not be applied while honey for harvest is on the hive.

In the draft, I asked a series of specific questions, following this note:

1. Our questions below relate solely to application by beekeepers of unregistered, generic, purified oxalic acid, formic acid, thymol, or food-grade plant essential oils (hereafter referred to as “the above biopesticides”).
2. Our questions relate solely to a beekeeper acting as an end user, not as a producer or distributor — specifically regarding interstate transport.
3. As end users, we would merely be diluting the above biopesticides for application solely to our own hives.
4. Since our questions are about legal compliance with FIFRA, and since we may present the answers from EPA to our State Lead Agencies, we are asking for clear yes/no answers.

I ended the draft with “We thank you for working cooperatively with us beekeepers and our State Lead Agencies, and hope for an expeditious reply clarifying details for complying with FIFRA and state regulations.”

An Example of Our Situation

As an example of how ridiculous our current situation is, as I type these words (in February), the vast majority of our country’s beehives are currently in my home state (pollinating almonds), where due to oxalic acid not yet being registered in California, it is against the law for any beekeeper here to apply a single drop of oxalic acid to any of those two million hives with the intent to control varroa, and according to the Advisory, if they did, when they took their hives back home, they could be charged with distributing an unregistered pesticide! (Figure 5).

Fig. 5 At the moment of this writing, for roughly 80% of the beehives in America, it would be illegal to dribble oxalic acid (whether generic or registered Api-Bioxal) with the intent of controlling varroa, although it would be perfectly legal to use it to bleach your top bars! What a ridiculous situation we are in!

Postscript

I just had a joint meeting with the leaders of the American Beekeeping Federation and the American Honey Producers Association. Although their combined memberships apparently consist of fewer than a thousand beekeepers, they do represent those beekeepers who are willing to pay the price to give our industry a presence in Washington. I’m a member of both organizations, and strongly respect and support their opinions.

I asked their leaders whether they wished to submit my request for further clarification to the EPA. They were reluctant to do so, feeling that we’ve already gotten all the answers from the EPA that we’re likely to get, and that they didn’t want to waste their political capital to push further. As you might imagine, this was disappointing to me.

However, I’ve since spoken with others who feel that we should be more proactive, and not have our actions held back due to fear of the EPA, since our industry as a whole should strive to come into compliance with FIFRA. There are plenty of commercial beekeepers working to get into compliance, and who feel that we need clear answers regarding EPA’s policy regarding our “own use” of the unregistered Natural Treatments, so that we can then approach our own State Lead Agencies and request that they follow the EPA’s lead.

Practical application: Beekeepers are likely going to need to individually petition each of their own State Lead Agencies in order to freely use the generic Natural Treatments. It would be much easier for them to do so if the EPA better clarified its position on the details of how we can use them without creating unreasonable risk to the environment.

A Request for Help

I do not have the hubris to think that I should be the one to represent our industry, nor that I’m qualified to spar with EPA’s lawyers. I’m just a single beekeeper, asking a large government agency to explain their interpretation of the law –– something normally reserved for the courts.

When I acted on my own, the EPA ignored me until I got our national organizations to sign on. And even when they did answer, their lawyers deliberately avoided directly answering my question, and the Agency made no effort to “inform and educate” us regarding accepted uses. So good luck petitioning your own SLA without clear answers from the EPA!

I don’t know what to say to beekeepers who want to use unregistered oxalic or thymol. I don’t want to step on anyone’s toes, and feel that it’s important to address the EPA with a united voice. But unless the EPA’s roundabout confirmation that there is no federal restriction on one’s own use of unregistered Natural Treatments filters down to your SLA, it will likely remain illegal for you to use them.

Possible actions to take: So if there is indeed widespread beekeeper interest in pursuing getting our states to allow us to use unregistered Natural Treatments (again, New Zealand already does this), someone with political clout (a state or regulatory agency or beekeeper organization, or a friendly congressperson) will need to politely ask the EPA to answer our questions, or take them to court to force them to do so.

In addition, another proactive beekeeping friend of mine, Charlie Linder, is rallying our industry to ask Congress to pass an amendment to FIFRA in the upcoming Farm Bill –– adding oxalic and formic acids, thymol, and food-grade plant essential oils to EPA’s Minimum Risk Pesticides list (limited to application within beehives), which would open the door for inexpensive, off-the-shelf formulated products, as explained in this flow chart [[11]].

I’d be happy to help any state-level group or agency that wishes to move on this. You can read the draft of my letter at https://scientificbeekeeping.com/scibeeimages/2024-Response-to-EPA.docx and sign up for updates at https://scientificbeekeeping.com/scientific-beekeeping-newsletter/

Citations and Notes

[1] Credit to Dr. Frank Rinkevich.

[2] The Learning Curve: Part 4–The Synthetic Miticides. American Bee Journal, October 2009, and https://scientificbeekeeping.com/the-learning-curve-part-4-the-synthetic-miticides/

[3] Lubinevski, Y, et al (1988) Control of Varroa jacobsoni and Tropilaelaps clareae mites using Mavrik in A. mellifera colonies under subtropical and tropical climates. American Bee Journal 128: 48-52

[4] Elzen, P, et al (2004). Formic acid treatment for control of Varroa destructor (Mesostigmata: Varroidae) and safety to Apis mellifera (Hymenoptera: Apidae) under southern United States conditions. Journal of Economic Entomology 97(5): 1509-1512.

[5] Amitraz: Red Flags or Red Herrings? American Bee Journal, October 2014, and https://scientificbeekeeping.com/amitraz-red-flags-or-red-herrings/

[6] https://aapco.org/wp-content/uploads/2021/08/SFIREG-Letter-to-EPA-for-Managed-Pollinator-Issue-Paper-August-4-2021.pdf

[7] Advertising and own use guidance for compounds for management of disease in beehives https://www.mpi.govt.nz/dmsdocument/37901/direct

[8] https://scientificbeekeeping.com/scibeeimages/Letter-to-Linda-Hollis.docx

[9] https://www.epa.gov/pollinator-protection/advisory-applicability-fifra-and-ffdca-substances-used-control-varroa-mites#violation-fifra-ffdca

[10] SEC. 23. [7 U.S.C. 136u] STATE COOPERATION, AID, AND TRAINING.

(c) INFORMATION AND EDUCATION. —The Administrator shall, in cooperation with the Secretary of Agriculture, use the services of the cooperative State extension services to inform and educate pesticide users about accepted uses and other regulations made under this Act.

[11] https://www.cdpr.ca.gov/docs/registration/sec25/minimum_risk_flowchart.pdf

Experimenting with Formic Acid

Contents

Formic Vapors and their distribution. 1

Experiment #1: Applying Formic Pro on the bottom board, with a temporary top entrance. 2

Results. 5

Experiments on queen loss due to formic. 6

Experiment #2: Can you remove, and then reintroduce the queen?. 7

Experiment #3: Is it the formic or the bees that kill the queen?. 13

Discussion. 15

Citations and notes 15

Experimenting with Formic Acid

Randy Oliver

ScientificBeekeeping.com

First Published in ABJ March 2024

Formic acid is the trickiest miticide to use in hot weather, so I continue to experiment with various application methods to improve its efficacy, and to better understand why it sometimes causes queen losses.

Last summer I ran several small “quick and dirty” preliminary experiments with formic acid; in this article I’ll share three of them.

Formic Vapors and their Distribution

Formic pad fumes, depending on the concentration of the acid, are denser than air (Table 1) and will thus tend to settle in a hive unless the bees actively fan them away.

Table 1 Notice that the more formic acid is diluted with water, the less dense is the mixture of their combination of vapors as they evaporate (they evaporate together at about the same rate).

Today, formic is generally applied above the brood nest, under the assumption that its fumes will tend to sink down across the brood. But back in the day, Canadian beekeeper Jean-Pierre Chapleau promoted applying formic on the bottom board. This got me wondering whether I could slip a single Formic Pro strip into the lower entrance, then seal that entrance and force the bees to use a temporary top entrance. My reasoning was that the formic fumes would tend to pool near the bottom of the hive, and slowly diffuse upwards into the brood area, where the bees would be forced to fan in fresh air from above. That might result in better distribution of the formic fumes throughout the hive.

Experiment #1: Applying Formic Pro on the bottom board, with a temporary top entrance.

So on a hot day in July I tried it on a double-deep hive having a starting mite wash count of 34. The colony took the treatment well, with few dead bees in evidence the next day, and a mite count after 24 hours of zero! Excitedly, I set up several more hives the same way, but found that the great reduction in mites in the first test was an anomaly — I’d need a stronger dose.

So I made up temporary hive covers with ¾” x 3” openings, plus wedges to seal the lower entrances. I took starting mite wash counts from 13 hives in various conditions (mostly poor — since I didn’t want to sacrifice any “good” colonies), and replaced each hive cover with a ventilated lid. I then shoved a single Formic Pro strip into the entrance, and sealed the entrance with a wedge.

The formic vapors were thus “trapped” in the hive, and the bees needed to learn to use the top entrance for access and ventilation. The results were surprising (Figures 1-3).

Fig. 1 There were huge colony-to-colony differences in response across the board — some bearded up, others ignored the fumes! I took this photo a couple of hours after applying two strips of Formic Pro on the bottom boards.

Fig. 2 The next day, in two hives there were kills of 800 and 1000 bees. In others, there were no dead bees at all! Go figure …

Fig. 3 In some there was kill of open and sealed brood; in others no apparent effect on the older larvae or pupae.

Results

I’ll let you try to make sense of the results yourself (Table 2):

Table 2 (QR=queenright; QL=queen lost)

• Large colony-to-colony variability in response — some colonies tolerated the treatment, some didn’t!
• Clearly unacceptable adult bee kills in two hives.
• Good average mite reduction, but wildly inconsistent (compare hives 8 and 9).
• Surprisingly little queen loss.

We didn’t follow up on these colonies, but happened to perform mite washes on some of them about a month later (when prepping for another experiment). We were surprised by the number showing mite counts of zero at that time.

I followed up with another small experiment — allowing the bees a couple of days to get used to the top entrance before treatment — and plan to experiment more with the method.

Experiments on Queen Loss Due to Formic

Beekeepers often complain that application of formic acid in hot weather may result in the loss of some queens — especially if they are old or failing (the queens, not the beekeepers). But in our operation, we use that observation to our advantage. When we nuc up our colonies after almond pollination, we put the best-performing queens back into nucs for a second season. By late August, they apparently begin to run out of sperm, and their colonies naturally start to rear supersedure replacements. But there unfortunately aren’t enough drones around at that time for proper mating.

Luckily, by that time our last rounds of nucs have built up into strong singles — and need a second box of honey and brood. So we harvest most of the honey from the hives with second-year queens, and shake all the bees down into a single, along with their brood. We then hit that single with a strong formic treatment — typically in 95°F weather — in the hope of eliminating not only its mites, but its aged queen as well, so that we can then put that box of “clean” bees, brood, and honey on top of a single in need of stores for the winter.

OBSERVATION: When we actually try to kill aging queens with formic in hot weather, darned if half of them don’t just laugh at us.

This brings me back to a subject that I’ve written about previously [[1]] — is it the formic that actually kills queens, or do the formic fumes induce the workers to kill their mother? This question has bugged me since Dr. Amrine posed it years ago [[2]]. So when some opportunities arose in September, I performed a couple of small experiments.

Experiment #2: Can you remove, and then reintroduce the queen?

Based upon my finding that reducing the first-day flash off of fumes from Formic Pro pads pretty much eliminated queen loss [[3]], I wanted to look more deeply into this phenomenon. I’ve noticed that after a day or so, the bees become acclimated to the odor (and irritation) of formic fumes and often walk right over the pads. So I wondered whether temporarily removing the queen during the initial flash-off and acclimation process, and then reintroducing her after a couple of days, might reduce the “queen loss problem.”

So I ran a small experiment, which I’ll go through step by step (Figures 4-10).

Fig. 4 At 5:00 in the afternoon on September 22, with temperatures in the mid-70s F, I removed the queens from ten hives and caged them with seven attendants each.

Fig. 5 The test hives were all single deeps with 9-10 frames of bees. After I pulled the queens, I applied recycled Miteaway II pads charged with 50% formic acid (which applies an acceptably strong dose to a single), in a 1½” rim [[4]]. This photo was taken at noon a day and a half later, during which the average evaporation rate was 35 grams per day. Note that by this time the bees were well acclimated to the fumes.

Fig. 6 In the meantime I maintained the queens in an incubator at 86°F (30°C) and 55% RH, for 43 hrs. They each got a small plug of stiff candy for a food source, and I gave them a couple of drops of water every day.

At noon two days later I returned with the queens. To my surprise and dismay, two had died, with their heads stuck to the candy (I have no idea why — their attendants were fine). The others all appeared to be healthy.

The ambient temperature was 75°F, with some guards fighting off yellowjackets and potential robbers at the entrances. I gave each hive two puffs of smoke, and allowed their queen to walk back into the entrance of her hive. (Some were reluctant to walk in, apparently in response to the odor of formic fumes emanating from the entrances.)

Once I’d reintroduced all the queens, I lifted the hive covers to measure the evaporation rate of the pads during reintroduction (~39 g/day). To my surprise, one queen was already being balled on the top bars (Figure 7).

Fig. 7 This queen had made her way up to the top bars, where she then got balled! I brushed off the balling bees and reintroduced her at the entrance.

A half hour later, I tipped up the boxes to inspect the bottom boards, and again looked under the lids. Three queens were being balled on the bottom boards (including the earlier one), so I recaged them each with one attendant and pushed their cages between two combs away from the fumes. Two other queens were being joyfully mobbed by their workers (one in a ball hanging from a bottom bar), but with no signs of aggression.

Fig. 8 These bees on the bottom board were happy for Mom’s return. They mobbed her, but allowed her to walk freely.

Fig. 9 Three colonies aggressively balled their queens, which I rescued, recaged, and placed between two combs of bees.

A half hour later I repeated the inspections. One queen was still being happily mobbed on the bottom board, and in another hive the bees were balling one dead worker and one yellowjacket.

Fig. 10 Five out of eight queens were reaccepted without issue.

The next day, 24 hours after reintroduction, I repeated the inspections (including looking for dead queens in front of the hives). There was one worker being balled, but no signs of any queens dead or being balled. I re-inspected two days later. The three queens that I’d recaged due to balling were dead, but the rest were happily on the combs.

Results: Out of 10 queens, two died in the incubator, three were balled and eventually died in cages, and five were reaccepted during strong formic application. How’s that for another set of ambiguous results?

So I ran another experiment a few days later in another yard.

Experiment #3: Is it the formic or the bees that kill the queen?

The queen is the largest, best fed, and longest-lived bee in the hive. So why would she be more susceptible to formic fumes than would expendable workers? To see whether that was indeed the case, I exposed some queens and workers, side by side, to exactly the same formic fumes.

By now it was late September. I set up ten hives with second-year queens in single deeps containing 8-9 frames covered with bees. I caught and marked the queens, then placed them in push-in cages midway down a comb, off center, but below a fresh formic pad. The cages were placed over comb with no brood inside, but with open nectar (so that the queen would not be dependent upon the workers to feed her), and with 3 workers as attendants. All cages were placed facing a comb of brood, so that the caged bees would remain within the cluster. I applied MAII formic pads in early afternoon, made with 50% formic, in a 1.5″ rim. Temperature was ~80°F.

Fig. 11 It’s easy to make a handy push-in cage out of a wide-mouth Mason jar rim, with 1/8” hardware cloth soldered or glued in place. (I haven’t yet tried it, but 5-mesh hardware cloth might be used to function as a queen excluder.) I included three workers from the brood area with each queen, and placed the cages over open nectar, halfway down the comb, beneath the formic pad.

After several days, the formic had evaporated from the pads, and I inspected the cages to see how the caged queens and workers made out.

Results: Eight out of ten queens survived and looked fine. But in the cages of the two that died, the attendants were still alive. So some queens do appear to be more susceptible to formic fumes than are workers. But 8 out of 10 presumably old queens tolerated being trapped beneath a strong formic treatment just fine.

Discussion

Formic acid has some very desirable qualities as a mite treatment:

• It is fast acting (you can eliminate most all the mites in a hive overnight with a strong flash treatment).
• A strong dose can penetrate the cappings.
• It doesn’t contaminate the combs or honey.

But it also has its downsides:

• In hot weather it may induce queen loss — although I’m still not clear whether the majority of those losses are directly due to the fumes, or instead from being balled by their daughters. (Covering the upper side of Formic Pro strips with their wrapper will largely eliminate queen loss in hot weather.)
• Formic also exhibits great hive-to-hive variability in efficacy when it’s hot.

Formic is a great choice in early spring, since you can use it to create a short brood break to reduce swarming, and if a queen should be lost, the colony can easily rear a replacement at that time of season. But later in the season, due to lack of drones in my area, I’m concerned that any replacement emergency queens might not get properly mated.

Anyway, formic’s been used for many years, especially in Europe and Canada (where there is a greater choice of approved application methods). I can only hope that now that the EPA has spoken, that our state regulators will allow us to experiment with the generic liquid more freely.

Citations and Notes

[1] Oliver, R (2022) Formic Pro and queens In hot weather. American Bee Journal September 2022 https://scientificbeekeeping.com/formic-pro-and-queens-in-hot-weather/

[2] Amrine Jr, J, & R Noel (2006) Formic acid fumigator for controlling varroa mites in honey bee hives. International Journal of Acarology 32(2): 115-124.

[3] Oliver, R (2022) op cit

[4] This is not an approved method for varroa control, but since I was not applying the formic for pesticidal purposes, it was not against the law.

Welcome to the 4th Agricultural Revolution!

Contents

THE OTHER AGRICULTURAL REVOLUTIONS. 3

The First Revolution (The Neolithic Revolution) 4

The Second Revolution. 4

The Third Revolution (The “Green Revolution”) 5

The Fourth Revolution (“Agriculture 4.0) 6

The Almond Industry. 6

The Honey Industry. 7

Miticide Resistance. 7

FACTORS INVOLVED IN ALMOND POLLINATION. 8

Demand from the Almond Industry. 8

Climate Change and The Sustainable Ground Water ACT. 9

Progress in Almond Breeding. 10

BEEKEEPERS AND THE 4TH AGRICULTURAL REVOLUTION. 11

The Internet 11

Public Perception, Sensationalism, and Targeted Advertising. 11

Enter the Technogeeks 12

Internet of Things (IoT) and Hive Monitoring. 12

Advances in Technology. 13

Plastics in Beekeeping. 13

High-Tech Fake Honey vs. High-Tech Testing. 13

CITATIONS. 20

Welcome to the 4th Agricultural Revolution!

Randy Oliver
ScientificBeekeeping.com

First Published in ABJ February 2024

The 4th Agricultural Revolution (aka “Agriculture 4.0) involves the application of smart technologies such as artificial intelligence, biotechnology, the internet of things, big data, and robotics to improve efficiency and productivity. As with previous ag revolutions, it will likely disrupt the established order, including that between beekeepers and commercial agriculture (and perhaps even for bee-keeping itself).

I wrote this article in December, so that it could be published as we get the answer to the $64,000 question — is the bee supply going to be short or long for almond pollination this season? From late November through the end of January, migratory beekeepers talk and debate about the expected demand for, and supply of, bees for almond pollination. We share observations and opinions and make guesses and financial gambles. But every year we don’t find out what the actual situation is until early February, when the rubber hits the road.

But the road may be changing. In the December issue of this journal [[1]], my friend Charlie Linder wrote an excellent piece about two companies whose business plans have the potential to disrupt our industry. This may be the first indicator of how The 4th Agricultural Revolution may affect the beekeeping industry (Figure 1).

Fig. 1 BeeHero is unabashedly proud of the disruption they are causing [[2]]. They have applied “The Internet of Things” to hive inspections and grading for colony strength. Flush with cash from venture capitalists, they’ve released two Hollywood-quality sales videos — one for the growers, the other for beekeepers (each video claims that the target audience would make more money; how that works in a zero-sum game is beyond me).

Practical note: Our beekeeping industry, although largely dependent upon almond pollination, has done a dismal job as far as engaging with the almond growers and educating them about pollination biology and honey bee performance (other than not using certain pesticides and trying to spray at night). The growers are thus ripe for a good sales pitch, especially if they think that they can get more for less.

Their strategy worked, and BeeHero has suddenly become the largest pollination provider in the world. Not to be outdone, another startup, also with a pile of venture capital behind it, has a different idea for the future of pollination services (Figure 2).

Fig. 2 Instead of beekeepers hauling in truckloads of individual hives, Beewise instead want beekeepers to place their leased containers holding ten hives, robotically managed by Artificial Intelligence. Some beekeepers are understandably skeptical, but again, this company’s got a lot of venture capital behind it to spend on development and advertising.

Both companies are looking to capture a share of the current $400 million almond pollination market (targeting the roughly 10% paid for brokerage and grading services). Agricultural industries are understandably averse to disruption, but like it or not, in the words of Greek philosopher Heraclitus, “The only constant is change itself.”

Practical application: I’m not picking on these two companies (the founders are very likeable), but they are a harbinger of things to come.

I suspect that most hobbyists and sideliners will continue to enjoy “old school” beekeeping practices, but as far as our commercial industry is concerned, it appears that “the times they are a-changin’.” Due to a number of technological breakthroughs, there is a new Agricultural Revolution starting to take place.

THE OTHER AGRICULTURAL REVOLUTIONS

The First Revolution (the Neolithic Revolution)

Around 12,000 years ago, the invention of farming (as opposed to hunting and gathering) marked a transition from a nomadic lifestyle to fixed settlements, due to the need to attend cultivated fields [[3]]. Settlements and a steady food supply also allowed for the development of merchants, craftspersons, and scientists. Farmers weren’t dumb, and quickly learned how to improve their soils, irrigate, and selectively breed wild plants for traits better to their liking (Figure 3).

Fig. 3 I (along with Jeff Pettis) recently had the good fortune to visit the Sacred Valley of the Incas in Peru, and see the agricultural plant breeding site of Moray (elevation 11,500 ft). Built by the Incas in the 1400s, each precisely-crafted stone terrace (filled with transported soils), duplicated a different microclimate of the Inca Empire, and allowed for the development of thousands of varieties of potatoes, corn, and other crops. Each terrace was individually irrigated by underground culverts.

After seeing the incredible knowledge, ingenuity, and craftmanship of the Incas, it was obvious to us that although technology can advance, humans certainly aren’t getting any smarter!

The Second Revolution

This revolution occurred in the Netherlands and Britain between the 17th and the 19th centuries when farming became a business (coinciding in later years with the Industrial Revolution) [[4]]. It consisted of the technological innovations of larger farm sizes and far greater labor productivity, the improved plow, high-yield crops and crop rotation, chemical fertilizers, and increased selective breeding.

Beekeeping had been an agricultural industry since ancient Mesopotamia and Egypt, but changed little until the “Beekeeping Revolution” of the 1850s and ‘60s, when Langstroth designed his hive, Moses Quinby invented the smoker and started “commercial” beekeeping, Johannes Mehring brought us comb foundation, and Franz Hruschka invented the centrifugal extractor. Other than using trucks (rather than horses) for transport, many of us nowadays are still happy with using only slightly-improved variations of 1850s technology!

I had the opportunity at the 100th anniversary of the National Honey Show in England to purchase several beekeeping books published between 1890 and 1910 — how little our beekeeping has changed since (beekeepers were just as smart, observant, and innovative back then)!

The Third Revolution (the “Green Revolution”)

This revolution began with the invention of tractors and trucks with internal combustion engines during 1910-1920, which meant that we could start using fossil fuels rather than humans and draft animals for labor. But it really caught wind in the 1940s, when an Iowa-born agronomist named Norman Borlaug (who later won the Nobel Prize for being “The Father of the Green Revolution”) began working with Mexican scientists and farmers to apply technology learned in California: using disease-resistant, high-yield crops, hybrid seeds, synthetic fertilizers, and a new generation of pesticides (notably DDT).

In 1973, President Nixon’s Secretary of Agriculture, Earl Butz, infamously told farmers to “get big or get out” and to “farm fencerow to fencerow.” And for the first time since record-keeping began, per capita farm income exceeded that of urban Americans.

And then, starting in 1996, genetically-engineered crops hit the market: Roundup Ready soybeans and corn, and then Bt corn became commercially available. The use of glyphosate herbicides exploded (Figure 4), changing the face of agricultural lands, to the detriment of pollinators (due to lack of “weedy” forage). This was followed by the introduction of the neonicotinoid insecticides, and seed-treated crops — a controversial mixed blessing, since they replaced aerial spraying of some other nasty products.

Fig. 4 I shot this photo of some small farms in California recently, impressed by how every plot border had weed-free bare soil — fencepost to fencepost farming, with very little non-crop forage.

The 3rd Agricultural Revolution allowed the human population to explode, but is dependent upon unsustainable synthetic and extracted fertilizers, cheap labor, overpumped water, and lots of pesticides.

The Fourth Revolution (“Agriculture 4.0)

We’re now at the beginning of the 4th Agricultural Revolution as electronic technology comes of age, and production agriculture incorporates the Internet of Things (IoT), Artificial Intelligence (AI), blockchain and biotechnologies, gene editing, robotic labor, precision dispensing of agrochemicals, vertical farming, and solar energy (and who knows what else). Agriculture 4.0 is “exciting — as well as a bit scary … but then the two often go together” [[5]].

So let’s set the scene for how this revolution may affect our industry:

The Almond Industry

Back in February 2005 — due to miticide-resistant varroa, the invasive wave of Nosema (Varimorpha) ceranae, and other virus and disease issues -— for the first time, beekeepers were unable to supply nearly enough bees for almond pollination in California. Growers responded by tripling the offered price for hive rental, and the next year grudgingly paid even more, at which point I wrote to the editors of both beekeeping trade journals, pointing out that our industry had passed a watershed moment — for the first time, the income received by beekeepers for pollinating almonds surpassed the income from total honey sales by our entire industry. We were now as much a pollination industry as we were honey producers, and most commercial beekeepers have been riding on the coattails of the almond growers ever since (incomes from almond pollination vs. honey have been running neck and neck).

Practical application: We’re awfully dependent upon the pollination needs of a single crop!

The Honey Industry

In the November issue of this journal [[6]] Ron Phipps had a great article about the negative impact on honey prices due to having to compete against “fake” and “adulterated” honey produced and exported from China and a few other countries. Chris Hiatt, as President of the American Honey Producers association, spoke at Apimondia about honey food fraud and how devastating the economically motivated adulteration of honey is to small family-owned enterprises throughout the world (not to mention our large commercial honey producers).

Practical application: Hauling hives to pollinate almonds is a costly pain in the rear. And even today’s high rental rates do not cover operating costs for the season, so the beekeeper still needs additional sources of income — honey generally being the main one. But cheap imported fake honey used by the food industry lowers the bottom line for all honey prices, and threatens the viability of our legitimate domestic honey producers.

Miticide Resistance

When varroa arrived, lacking resistant bee stock, we jumped straight to synthetic miticides as a stopgap measure (Figure 5).

Fig. 5 This is a Powerpoint slide that I created to illustrate the IPM pyramid for varroa. Control of varroa with any synthetic miticide is only a stopgap measure — we’ve watched fluvalinate and coumaphos fail. Amitraz has held the mite at bay for a long time, but the writing’s on the wall.

Our commercial beekeepers, by not rotating treatments with different modes of action, have been remarkably successful at selectively breeding for resistant mites. Indeed, some beekeepers are now making 15-20 applications of amitraz a year. Without taxpayer-funded ELAP payments, many commercial operators would be hurting.

Practical application: Due to the lack of any new “silver bullets,” many commercial beekeepers are finally having to learn to use organic acids and thymol. But the real revolution will take place when our commercial queen producers are finally able to supply proven mite-resistant stock (that may not be long!).

In summary, our current scene is that our beekeeping industry is half dependent upon high rental rates for almond pollination, is being hurt by low honey prices due to competition from fake honey, and is dealing with the need to shift from amitraz. The Fourth Agricultural Revolution will involve all three, especially with regard to almonds, so let’s start with that first.

FACTORS INVOLVED IN ALMOND POLLINATION

Demand from the Almond Industry

The almond industry has been on a joyride for nearly twenty years, and we beekeepers have been along for the ride. But as with any other crop, if it’s profitable, it will eventually get overplanted, and supply will exceed demand. That’s the situation now for the almond growers — there’s a glut of almonds on the market, so the price has dropped (Figure 6). At the same time, fertilizer and all other operating costs are skyrocketing.

Fig. 6 A glut of nuts! Is the joyride over? Photo credit Todd Fitchette, Farm Progress.

Practical application: Growers are feeling the pinch, and are putting pressure on beekeepers to drop their prices (it’s kind of a game of chicken) or to cut back on the stocking rate.

Climate Change and the Sustainable Ground Water Act

The California Central Valley has long been the premier spot to grow almond trees, and we supply over 80% of the world’s demand for this tasty and nutritious nut. But our current farming methods are unsustainable, especially with regard to the water supply.

For quite a few years now, it’s been a race to the bottom, as farmers competed to see who could drill the deepest well to pump precious water out of the ground, resulting in the subsidence of the soil level throughout the San Joaquin Valley (Figure 7).

Fig. 7 Almonds are grown throughout the California Central Valley. The Sacramento Valley is to the north, but the majority of orchards are in the southern San Joaquin Valley (shown). Land subsidence due to overpumping there has been stunning. This chart shows the number of meters of subsidence between 1926 and 1970 [[7]](one dark area had dropped a total of 30 feet)! The rate has slowed a bit, but increases in dry years when there is less surface water available.

As a result, California is instituting the Sustainable Groundwater Management Act (SGMA). That, drought, and climate change are forcing some growers to abandon their orchards, or convert the land for other crops or uses (such as pistachios, agave, or solar panels).

Practical application: There may be a decrease in demand for hives, at least for the next few years.

And there’s an additional potential disruptor on the near horizon:

Progress in Almond Breeding

Almond pollination is all about the sex act — the transfer of pollen grains from the male anthers to the female pistils, normally between two self-incompatible cultivars. But what grower wants to pay big money for a beekeeper to haul in pollinators? So plant breeders have worked to develop self-fertile almond cultivars, such as Independence (which now accounts for about 8% of bearing acreage [[8]].

Luckily for those of us in the pollination biz, even Independence benefits from bees (although stocked at only half the normal number of hives per acre). But there’s a new nut in the neighborhood — Yorizane is a self-pollinating almond variety developed by USDA’s Agricultural Research Service, with superb consumer traits such as size, color, and flavor [[9]]. Yorizane has been in field trials since 2014, and due to its flower structure, may not need bees at all [[10]].

Practical application: Yorizane may well displace the current favored cultivar, Nonpareil. If so, we migratory beekeepers (not to mention BeeHero and Beewise) could lose an important source of income. Unless we figure out how to deal with honey fraud, we could be in serious trouble.

BEEKEEPERS AND THE 4TH AGRICULTURAL REVOLUTION

The Internet

The internet has been a mixed blessing for beekeepers. We now not only have the world’s libraries at our fingertips, but are suffering from information overload — much of it erroneous, biased, sensationalized for marketing purposes, or just junk. Back in the day, published information was generally filtered through editors, who reviewed, checked, and corrected it. As I previously mentioned, there were of plenty of well-written and informative beekeeping books and journals by 1900. “The British Beekeepers’ Guide Book” had by 1904 already sold 50,000 copies (one for every thousand Britons), and was releasing a second edition (this on top of a large number of other excellent beekeeping books available for a beekeeper to read at their leisure).

Compare this to beekeepers today getting much of their information from the screen of a cell phone. The most common thing that I hear from beekeepers today is that “I saw on the internet that…” (Figure 8).

Fig. 8 I got over five million results for a search for basic information on beekeeping! And yet we keep hearing of colony loss rates being unacceptably high. Too much information may be worse than too little. Despite so much information being available, I’m still acutely aware of the degree of my ignorance of bee biology, and continually hit dead ends when seeking answers to important questions.

Public Perception, Sensationalism, and Targeted Advertising

Any time you look at a computer or cell phone screen, a billboard, TV, newspaper, or magazine, you are continually being brainwashed by advertising designed to grab your attention. The honey bee has been hijacked as a poster child by any group wanting to raise money or sell a product. Although this has created a huge hobby demand for those who want to help “save the bees,” we beekeepers must continually be aware of, and counteract, any negative perceptions about our industry or our products (notably honey). Always remember the lesson of the Alar Scare — when sensationalized fearmongering “news” temporarily devasted the apple industry [[11]].  Media outlets vie for the catchiest headlines (Figure 9).

Fig. 9 The above headline in The Guardian [[12]] and Men’s Journal [[13]] got the attention of consumers, especially those in Europe. Such perceptions can reduce the demand for almonds, which could indirectly hurt those of us who get paid for pollination.

Enter the Technogeeks

For some reason, many innovators wind up sitting with me on my deck, asking my opinion of their whiz-bang invention, having questions on how they might improve and market it, and sometimes asking me to advise or collaborate. A number of them are technogeeks showing up with what I call “a solution looking for a problem.” These are mainly hive monitoring devices and systems that in the past would have only been of interest to a subset of researchers, but now are available to any beekeeper wanting to find out anything about their hives by looking at their computer screen.

Internet of Things (IoT) and Hive Monitoring

Beekeeping is labor intensive, and like other livestock husbandry, making a profit is very much dependent upon how well the beekeeper understands and monitors the health of their colonies, while minimizing their amount of labor. The Internet of Things refers to a network of physical devices, vehicles, appliances, and other physical objects that are embedded with sensors, software and network connectivity that allows them to collect and share data. Remote monitoring of colonies may free a beekeeper from the need to physically open a hive to “inspect” it.

Practical application: For those beekeepers handy with a computer or cell phone, a world of techno-monitoring equipment is available — there are now plenty of devices available to track temperature and humidity, weight gain or loss, bee flight, swarm preparation, mite levels or hive theft, or to organize recordkeeping (Figure 10).

Fig. 10 There are now any number of apps available for hive monitoring and recordkeeping. Advice: if you’re on a date, don’t let her catch you paying more attention to a hive than to her!

Call me “old school,” but understand I began keeping bees prior to the invention of cell phones and computers, and love working outdoors and getting dirty. Nothing is more thrilling to me than the energy emanating from a hive in springtime, reveling in an abundant nectar and pollen flow. And the joy of seeing a queen that I reared on a perfect frame of brood. Although many of us love the magic and lifestyle of beekeeping, and the soul-smoothing vibe that we experience each time we open a hive, a beekeeper now has the option of monitoring their hives from a computer screen in their office. Hobby and sideline beekeepers will of course continue our connection with Nature, but the commercial industry is now grappling with adapting to new technologies.

Practical application: These devices give curious beekeepers a chance to gain insight into what’s happening in their hives, but commercial guys may mainly be more interested in a simple system that alerts them each morning to any needed action items in their outyards (which can largely be determined by simple weight monitoring).

Advances in Technology

Plastics in Beekeeping

It was difficult for me to switch to plastic foundation, but I’ve held the line there — I’m personally hesitant to use plastics that I can’t recycle. So how about polystyrene hives? They have certain advantages (bears like them), but my question is, what are you going to do with them when they wear out? They are not currently economical to recycle, are seriously polluting if burned, and can create an environmental mess as they degrade. We’re going to need to come to terms with non-burnable bee equipment.

High-Tech Fake Honey vs. High-Tech Testing

Fraudsters have figured out how to produce fake or adulterated “honey” from cheaper ingredients, such as sugar syrups made from cane, corn, rice, or beets, or from unripe harvested nectar, filtered through advanced resin technology, and spiked with ingredients to pass traditional methods of testing for purity. So it’s now a technological race between the fraudsters and the testers (Figure 11).

Fig. 11 Dr. Peter Awram of True Honey Buzz [[14]] using nuclear magnetic resonance technology to identify honey to its source

Agriculture 4.0 has also brought about the dawn of synthetic or cultured (vs. naturally-grown) foods, such as plant-based meat alternatives, vegan cheese, lab-grown meat, and synthetic “honey” (Figure 12).

Fig.12 MeliBio [[15]] is a startup that has taken synthetic honey to a new level, by selling it with the pitch that “the commercial production of honey is destroying the biodiversity of our planet and wiping out our native bee populations. … By choosing MeliBio’s honey without bees, you’re joining us in our mission to create a kinder, more sustainable future for humans and bees alike.”

Not to be outdone, Israeli startup Bee-io is on their tail (Figure 13).

Fig. 13 Bee-io [[16]] promotes their product by claiming that “cultivated honey is pure, baby-safe, and 100% bee-free” and “lacking the bad materials that are very common in natural honey.” And they go on:

“Bee-io aims to eliminate human nutrition dependency on bees. The existing method of honey production endangers bees and results in escalating prices … the honey produced [by bees] may contain toxins, pesticides, and antibiotics.”

Warning! These companies are potential disruptors in three ways:

1. They are hijacking the name “honey” for a product that is not honey.
2. The main reason that people pay more for honey than they do for sugar is their perception that honey is a more natural and “healthier” sweetener, and that they are helping the bees. The marketing strategies of these companies are to badmouth natural honey, honey bees, and beekeepers (read Melibio’s damning report at [[17]]). This sort of disparaging advertising gives us and our product a black eye.
3. And if these legit companies can make fake honey indistinguishable from the real thing, the black-market fraudsters will not be far behind!

Practical application: I’m not clear on how making fake honey from sugars extracted from agricultural crops can be more eco-friendly than honey made from nectar harvested from wildflowers, but it is clear that the marketing strategy of these companies (awash in cash for advertising) will be to disparage our natural product. Our industry should create a task force to address this issue!

New Inventions and Products

The Israeli Startups

Israel has been nicknamed the “startup capital of the world,” since it has the most start-ups per capita. Seeking a larger market, many Israeli ag-related startups come to California, so I’m not surprised that several have shown up at my place. When the innovators ask me who their potential market might be, I explain the differences between the hobby vs. the commercial markets, and the fact that most beekeepers don’t do it for the money, but rather because they love keeping bees, being outdoors in nature, and the challenging lifestyle involved.

So I’ve twice suggested that a startup might have better luck pitching their product to the big fruit and nut growers (I now kinda regret making that suggestion).

Practical application: I’ve previously worked with two startups funded by venture capital. Those investors gamble big money, hoping for an eventual large return on their investment. So this puts huge pressure on the startup to start showing success, so I’m not surprised that these startups are coming on strong.

The Brokering of Pollination Services

BeeHero developed an IoT monitoring device that they claim can tell you all kinds of things about your colonies, notably how strong they are (they have recently invited me to confirm their claim in the orchards). At first they tried selling their system to beekeepers, but then shifted to instead targeting the growers paying for pollination services, with the motto “Get Premium Bees & Pollinate Your Crops With Precision.”

I’ve pollinated almonds for over 40 years. My favorite contracts are those in which 10% of our hives are randomly graded for strength by the broker, and we get paid accordingly — a practice that I strongly support, since not only does the grower get what they’ve paid for, but we get rewarded for having strong colonies [[18]].

BeeHero claims to be able to do exactly that (but grading every single hive): “BeeHero’s mission is to deliver pollination accountability for commercial crop growers, by leveraging big data analytics and machine learning to help them mitigate pollination risk.”

Practical application: Those of us who have enjoyed fat checks for almond since CCD, are starting to see disruption of our relationships with “our” growers and established brokers. Again, I’m not saying this is good or bad, but not every beekeeper or broker is happy with a newcomer muscling in, nor wanting to sign a contract with a company that requires them to place an electronic monitor in every one of their hives. It’s gonna be “interesting” to see how this all works out!

Mechanical Pollination

Similar to those hawking the “honey alternatives” who are telling us to eliminate bees from the picture, companies involved with robotics are trying to do the same thing with regard to the honey bees’ other nasty habit — that of pollinating flowers (Figures 14-16).

Fig. 14 Israeli startup Edete Precision Technologies for Agriculture’s proprietary 2BeTM autonomous pollinator. The company is running trials in California almonds [[19]].

Fig. 15 The StickBug from West Virginia University, which could be used for greenhouse and vertical farm pollination

Fig 16 And then there are startups and universities developing miniature drones to perform robotic pollination (but not insemination). “Dutch scientists say they can create swarms of bee-like drones to take over if the insects die out.” Image from [[20]].

Practical application: I can see a potential market for mechanical pollination in greenhouses, but can’t imagine the logistics of the maintenance and battery charging involved with a swarm of robotic drones. When I’ve monitored colony flight in almonds on cool or rainy days, foragers may only fly for less than an hour. The huge advantage to the grower is that honey bees don’t need to be programmed, or stored for nine months of the year — they are eager to pollinate blossoms the moment that the temperature is high enough for the pistils to be receptive.

Robotics

California farmers and commercial beekeepers have long depended upon cheap labor from skilled and hard-working employees from Mexico and elsewhere, who were willing to perform the physically-demanding, hot, and dirty work that spoiled Americans were unwilling to do. But this labor pool is contracting, and technologists involved in robotics are seeing market opportunities for a 4th Agricultural Revolution. This also applies to beekeeping.

The Israeli company Beewise (mentioned at the beginning of this article) has invented the BeeHome — an enclosed container that holds hives of bees, and can manipulate every frame robotically, using AI to identify bees, brood, and honey, as well as disease. Their system is truly remarkable.

Their business plan is now to lease these containers to beekeepers, and provide pollination services to growers. Beekeepers then run their bees in BeeHomes, placing the containers in areas of forage (where the beekeeper can make honey) while not on pollination contracts. (I’m not clear on how involved a beekeeper will actually be with hands-on management of their colonies, nor the specifics of their contract.)

Practical application: Many of us are riding on the coattails of the almond growers, who may eventually not even need us. In the interim, expect some disruption as Beewise competes with BeeHero to take over pollination services, although I suspect that there will still be a place for independent beekeepers and old-school established brokers for a while.

Artificial intelligence (AI)

I left this hot topic ‘til last. From an IBM webpage: “Artificial intelligence leverages computers and machines to mimic the problem-solving and decision-making capabilities of the human mind.”

Artificial intelligence (AI) has unlimited (and scary) potential. It’s a huge unknown that could completely revolutionize agriculture, and either finally separate humans from nature, or allow us to enjoy “virtual” nature, or perhaps somehow “reduce” the size of the human population to come into balance with Earth’s ecosystems in a sustainable manner.

Large-scale commercial agriculture will likely be the first to embrace Agriculture 4.0. A farm may be managed by AI, which could choose the most profitable crops to plant, instruct the GPS-coordinated self-driving tractors precisely where to plant and fertilize, and control the robotic weeders and harvesters to complete the job. Will commercial beekeeping take the same path?

On the other hand, lots of us enjoy living on the land, growing our own food, tending our bees, and living with nature. The only constant is change. The world has changed tremendously in my lifetime; it’s hard to imagine how it will look when my grandchildren are my age.

For what it’s worth, ChatGPT told me that “The Fourth Agricultural Revolution … poses challenges that will require continuous adaptation, collaboration, and innovative solutions within the beekeeping industry.”

Practical application: I’ll give AI the last word. I wondered whether Artificial Intelligence could solve the classic beekeeping problem: “Ask ten beekeepers a question, and you’ll get fifteen different answers.” So I of course ran an experiment. I asked ChatGPT the question “Should I insulate my beehive?” and got a very nice generic answer. I then asked the same question twice again, and received a completely different answer each time. Nope, AI didn’t solve the problem. But the last paragraph of one of the answers gave me hope (Figure 17).

Fig. 17 ChatGPT wrapped up its generic answer (not realizing that we all keep the same species) by sending us back to human beekeepers for advice. So you may as well go ahead and ask ten of them for their opinions!

Feedback

Beekeeper Derek Lewis pointed out that had we beekeepers not risen to the challenge of pollinating the huge crop monocultures, that the human population may not have grown to its current overload.

CITATIONS

[1] Linder, C (2023) BeeHero and Beewise. American Bee Journal 163(12): 1339-1342.

[2] Image from https://www.beehero.io/news/beehero-makes-the-2023-cnbc-disruptor-top-50-list

[3] https://intellidigest.com/food-production/agriculture-4-0-the-fourth-revolution/

[4] https://populationeducation.org/a-timeline-of-the-three-major-agricultural-revolutions-in-history/

[5] https://www.oliverwyman.com/content/dam/oliver-wyman/v2/publications/2021/apr/agriculture-4-0-the-future-of-farming-technology.pdf

[6] Phipps, R (2023) International Honey Market Report. American Bee Journal 163(11): 1169-1174.

[7] https://www.usgs.gov/media/images/land-subsidence-san-joaquin-valley-california-1926-70

[8] https://www.almonds.com/sites/default/files/2023-04/2022_NASS_Acreage.pdf

[9] https://www.ars.usda.gov/news-events/news/research-news/2021/researchers-develop-self-pollinating-almond-with-a-gold-mine-of-tasty-traits/

[10] https://journals.ashs.org/hortsci/downloadpdf/journals/hortsci/56/9/article-p1142.xml

[11] https://www.acsh.org/news/1999/02/01/an-unhappy-anniversary-the-alar-scare-ten-years-later

[12] https://www.theguardian.com/environment/2020/jan/07/honeybees-deaths-almonds-hives-aoe#maincontent

[13] https://www.mensjournal.com/food-drink/industrial-almond-farming-killing-bees

[14] https://truehoney.buzz/the-solution/

[15] https://www.melibio.com/

[16] https://bee-io.com/

[17] https://uploads-ssl.webflow.com/64248b6809fb11548c023516/644ffe7d49a93c12d4d23fb7_The%20State%20of%20the%20Bees%20Report.pdf

[18] https://scientificbeekeeping.com/determining-the-relative-value-of-hives-for-almond-pollination/

[19] https://edetepta.com/post/precision-pollination-contributes-28-increase-of-almond-yield/

[20] https://www.fao.org/e-agriculture/news/robotic-bees-could-pollinate-plants-case-insect-apocalypse

Good News from the EPA !

Good News from the EPA!

Randy Oliver
ScientificBeekeeping.com

First published in ABJ January 2024

Last month I wrote about a letter that I written in July to the EPA, asking for clarification as to whether they actually had authority under FIFRA to justify restricting beekeepers from using generic oxalic acid (and other natural treatments) in their own hives, since they had a mandate to do so only if they had determined that such use would pose unreasonable risk to the environment.

We finally got an answer

In early November, me and some other leaders of our industry were invited to a Zoom meeting in which members of the Biochemical Pesticides Branch informed us that EPA was not going to restrict such use.

 High five — this is great news for our industry!  Charlie Linder has been very involved and active, working with our lobbyist Fran Boyd, to represent both ABF and AHPA in Washington, D.C.  Here we are celebrating EPA’s (verbal) answer at the California State Conference.  Photo by Rob Stone.

Upon hearing this clarification, I requested the Biopesticides Division to please ask their Office of Enforcement and Compliance Assurance to inform all State Lead Agencies of this decision.  At the time of this writing, we’re still waiting for written confirmation.  Beekeepers in each state may need to clarify their own state’s position.

This does not mean that anyone can go ahead and sell any product as a varroacide without first getting it registered.  It only means that beekeepers are not restricted (at the federal level) from using the generic substances for their own use, within the confines of their own hives.  We of course can continue to use any currently, or soon-to-be registered products (there are at least three companies (that I know of) currently in the registration process for OAE formulated products).

This decision means that individual beekeepers may by next season be able to also legally prepare and apply their own oxalic acid, thymol, formic acid, or essential oil treatments using off-the-shelf ingredients (being careful not to add any contaminants).

Practical application: We are currently in cooperative discussion with the Biochemical Pesticides Branch as far as them offering guidance to beekeepers for such use.  To be clear, no sale or advertisement of the generic products for pesticidal purposes will be permitted.

This decision by the EPA is a game-changer for us.  As I have previously written, a representative from the EPA had already stated that the Agency did not require beekeepers to obtain an Experimental Use Permit to experiment with oxalic acid for mite control, but our State Lead Agencies didn’t get the message.  With luck, by next season those beekeepers wishing to save money, invent better application methods, or engage in experimentation to bring novel formulated OA products to market will be able to do so without fear of enforcement action against them.

This confirmation from the EPA that beekeepers are not restricted (at least at the Federal Level) from using the generic natural substances in their own hives opens a new world of mite control to us.  With luck, the State Lead Agencies will follow the EPA’s lead.  This newfound freedom opens up opportunity for beekeepers to not only save money (and not break the law), but to also opens the door for experimentation to improve, develop, and (possibly) register novel application methods and formulated products.

But there’s also some potentially bad news

Talk about rain on our parade — we recently learned that EPA is planning on passing the baton to the FDA as far as registration, sale, and use of products for varroa control (see Charlie’s article in this issue).  We’re working on seeing whether we can cement in some sort of exemption for the generic substances before that happens.  Wish us luck!

Acknowledgements

Thanks to Charlie Linder and Fran Boyd for their assistance in my dealings with the EPA.

Update: Due to the hold on posting my articles to this website, things have greatly advanced from here.

2023 Field Trial of Matrices and Formulations for Extended-Release Oxalic Acid

Contents

A Large Field Research Project 1

Materials and Methods 2

Experimental design. 2

Surface Area of the Treatments 4

Justification for the Ratios Tested. 4

The Test Colonies 4

The Matrices 7

Dose applied to the bees 13

Results. 14

Summary of my interpretation of the chart 16

Discussion. 16

Musing on other studies 17

Final Notes. 18

Acknowledgements. 18

Citations and notes 18

2023 Field Trial of Matrices and Formulations

for Extended-release Oxalic Acid

First published in ABJ January 2024

Randy Oliver

ScientificBeekeeping.com

The extended-release method for oxalic acid (OAE) is becoming widely used throughout the world, notably where mites have developed resistance to the overused synthetic miticides. This year we ran a field trial to compare the efficacy of various application methods, matrices, and ratios of OA to glycerin.

See my associated announcement in this issue about EPA allowing us to use generic oxalic acid for varroa control. While we were waiting for an answer, I continued my research on extended-release application (OAE).

A Large Field Research Project

I receive a lot of questions from beekeepers about using OAE in their hives. I’m often unable to give definitive answers, since this is still experimental research in progress, with updates in this journal, and at my website [[1]]. Five questions continue to pop up:

1. What is the cheapest and/or most efficacious matrix to use?
2. What is the best formulation (ratio) of oxalic acid to glycerin?
3. Is it better to use pads laid flat on the top bars, or strips hung between the frames?
4. Does it help to replace the pads or strips after a month?
5. When is the best time of season to apply the strips?

This summer we ran a large field trial to attempt to help answer the first four questions.

Materials and Methods

Experimental Design

Due to the inherent variability between colonies in any field trial, in order to tease out “the signal from the noise” one must use a large “n” of test hives for each test group, and replicate the trial in different yards. This is especially the case with varroa treatments, since there are often substantial hive-to-hive differences in the efficacy of exactly the same treatment.

So I decided to run a large-scale trial in five different apiaries (for replication), and to test each of five different matrices with three different ratios of oxalic acid to glycerin, degree of saturation of the matrix, and whether the treatment was applied only once or replaced at 30 days. My plan was to then use analysis of variance (ANOVA) to tease out the differences between each variable. For example, by testing each formulation ratio on five different matrices, I could look for consistencies for the efficacy of the ratio independent of the matrix (and vice versa). This design would hopefully allow me to get the most informative results from a single trial.

I’ve written previously about my testing of various absorbent application matrices [[2]], looking for matrices that were biodegradable and non-contaminating, easy to prepare, apply, and remove, efficacious in delivery, and inexpensive (perhaps the most important consideration for commercial beekeepers). My favorite to date were the Swedish sponges sold as “If You Care” brand [[3]], which I used as a “known” positive control (since at the 1:1 ratio it was a treatment combination that had a history of working well for us).

In some previous trials, I had tested chipboard hung strips from New Zealand, where the recommendation has been to use a 1:1.5 OA:gly ratio, and to replace them after a month (since the hung strips tend to “dry out” and be chewed away by the bees; Figure 1). I was curious as to (1) whether a different ratio might be more efficacious, and (2) whether the amount of benefit from replacement was worth the cost of the labor involved.

Fig. 1 Freshly-prepared strips to the left; to the right strips removed 65 days after application. These strips tended to “dry out” more quickly than did the other matrices (perhaps having something to do with gravity), but may have continued to dispense oxalic acid onto the bees during the process of chewing and removal. I thank the manufacturer of the strips (Beequip, New Zealand [[4]]) for generously donating the raw strips for this project.

Based upon preliminary experimentation, I also tested using citric acid rather than oxalic. Citric acid provides roughly the same amount of total acidity gram-for-gram as does oxalic, but it is not as strong an acid. Citric has the huge advantage of being on EPA’s Minimal Risk Pesticide list.

Table 1 shows the 18 different matrix, acid, and formulation ratios tested.

Table 1 The variables were the 2 acids, the 5 matrices, and the three formulations, resulting in 18 different treatments to test.

Surface Area of the Treatments

I’ve previously determined that the number of square inches of matrix surface area is critical for efficacy [[5]]. But it’s really the amount of acid on that surface — as opposed to any hidden deep within the matrix — that allows for distribution by the bees and transfer to the mites.

Important note: All flat-laid treatments for this trial were cut into two pads having a total surface area equal to that of the Swedish sponge: 60 square inches. Surprisingly, the recommended application rate of 6 hung New Zealand strips provides nearly twice as much exposed surface area: 112.5 square inches. And that doesn’t take into account that most of the surface area of the flat-laid pads is blocked by the top bars, whereas the bees are exposed to both sides of the hung strips. I know — this observation is completely contrary to “common sense,” so go figure!

Again surprisingly, I found in previous testing that if that large amount of saturated chipboard is instead laid flat, that it can overdose the bees, and cause serious agitation, bearding, and brood kill.

Justification for the Ratios Tested

Our “positive control” formulation was the 1:1 (weight:weight) ratio that we’ve used for years. Maggi [[6]] used a 1:2.5 ratio, so I split the difference between it and the preferred New Zealand 1:1.5 formula, and tested a 1:2 ratio. In addition, Kanelis [[7]] suggested using a 1:2.7:1.7 (OA:gly:H₂0) ratio. This solvent-heavy ratio would have put very little oxalic acid into the matrices, so I included a 1:2:1 ratio, which results in a “drier” feeling matrix, similar to the first ratio that I used with shop towels [[8]].

The various formulations resulted in a range of the amount of total oxalic acid applied per hive (Table 2), although with the more absorbent matrices, plenty of OA remained in the matrices at the end of the trial 65 days later.

The Test Colonies

An added difficulty for me is that (as I described in September [[9]]) some of the colonies that I had at my disposal turned out to be mite resistant (what a bummer), and thus would not be suitable for testing the efficacy of a treatment against varroa. So I could only use colonies which exhibited a buildup in their mite levels.

Experimental limitation: It’s nearly impossible to equalize the mite infestation rates of a starting group of colonies, since over half the mites are typically in the brood, and the mite population and reproduction dynamics can vary greatly from hive to hive. I dealt with this issue by using a randomized block design to assign treatments (stratified assignment by their mite counts after 3½ months of mite buildup), thus not only minimizing the effect of this variable, but also allowing us to test the effect of treatment over a range of infestation rates.

I could only scrounge up enough colonies with high enough mite counts to allow me an “n” (number of replicates) of 12 hives per treatment (the minimum that I’ll use), but since each matrix was applied to 36 hives, and each formulation ratio to 72 hives, I hoped that this repetition would allow me to tease out useful findings. So we applied treatments to 18 x 12 = 216 hives in total (Figure 2).

Fig. 2 We numbered all the test hives in the five yards, sorted them by starting mite count, and randomly assigned treatments to each tier of 18 (a randomized block design). At each yard, we spread out the 18 tubs, and very carefully applied the assigned treatment to each hive. Here Brooke is acting as the supervisor “Hawk,” tracking and recording confirmation that Rose took each treatment from the right tub and placed it on top of the correct hive for insertion.

Since the three formulations for each matrix looked similar, we had to be very careful, and actually (due to a possible error in proper application) in two yards replaced all of two treatments the following day (I’m a stickler for getting everything exactly right). The colonies varied in strength, but all had bees in both the upper and lower boxes.

The ladies did a great job at distributing and applying the treatments, but they weren’t quite up to lifting 216 heavy upper brood chambers (Figure 3).

Fig. 3 It was dang hot as we set up the trial (Figure 4), and I supplied the muscle to crack open each hive for inspection and insertion of the treatment. The surfaces of our dark hive covers reached over 150˚F, and just resting them against my bare arm when I tipped them up would send a flash of heat through my body. I had to pause from time to time from lifting the heavy boxes to avoid heatstroke! Thank goodness that we keep gentle bees that don’t require us to wear much protection.

Fig.4 The weather started out very hot and dry as we were performing mite washes and applying treatments, then cooled off a bit. Daytime humidity was low early on, but briefly got high in early September (there was no rain during the trial). Data from KCAGRASS50 (2523 ft elevation).

The Matrices

In order to introduce you to the matrices that we tested, I took photos of Rose applying them to some hives (Figures 5 through 10).

Fig. 5 Our “positive control” was a Swedish sponge (If You Care brand) cut in half. All flat-laid treatments were laid on the top bars of the lower brood chamber, to the front and the rear of the hive, centered on the cluster. This enabled us to feed pollen sub to encourage brood rearing during the dearth (to allow for the mites to continue to reproduce).

Fig. 6 I had dismissed corrugated cardboard during previous exploratory testing, since the adhesive of the pieces that I tried fell apart in the hot oxalic solution. But I recently noticed a shipping box made from double-layer, eco-friendly corrugated cardboard [[10]] and gave it a quick test, which suggested that its glue might work for us. I confirmed that the double-corrugation board could absorb a lot of oxalic solution, so I included it in the trial, since as a matrix it would be readily available to penny-pinching beekeepers.

Fig. 7 Unfortunately, we found that after a couple of days in the tub, the corrugated pads tended to delaminate, making them a bit difficult to apply and to later remove. But the price is right!

Fig. 8 I ordered chipboard sheets (similar to that used for the New Zealand hung strips) from Uline [[11]]. They took some time to absorb the solution, but were easy to install and remove. You may have noticed that we’ve shifted from using nitrile gloves to food handling gloves, which not only provide adequate protection, but are much easier to get on and off sweaty hands. And because they are so inexpensive we don’t hesitate to remove (and properly dispose of) them any time that we want our hands to be free of gloves (or acid).

Fig. 9 At the suggestion from a beekeeper whose name I’ve sadly misplaced, I tried King Zak biodegradable towels [[12]]. These towels, although thin, were surprisingly absorbent, and remarkably strong (they held together for removal after 65 days). They look promising for further experimentation.

Fig. 10 For hung matrices, we applied Beequip’s 1¼” x 15” chipboard strips at the rate of 3 strips per brood chamber [[13]]. As pointed out previously, this results in a far greater amount of surface area exposure to the bees than with the flat-laid pads. The hung strips, although a bit more tedious to apply, work well for treating nucs or single brood chamber hives.

Following recommendations from New Zealand, I’d planned on replacing the hung strips in half the test hives with fresh ones at 30 days. However, when the time came to do so, I decided to also replace all the pads in the other treatment groups in the same yards as well (in order to equalize that variable for all test groups). That then doubled the number of treatment groups to compare to a count of 36!

Dose applied to the bees

This brings us to the indirect dispersion of (by transfer by the bees) of the active ingredient — oxalic acid — and its exposure to the mites (the intended target) (Figure 11).

A teaser: I’ve been using chemical titration to track the actual amount of acid residues on the bees’ bodies resulting from various application methods of oxalic acid (and have presented my preliminary findings at conventions and on Zoom). I hope to soon publish my findings.

Fig. 11 Although we’re happy to see dead mites on the pads, in actuality it’s unlikely that they died from direct contact — it’s the amount of acid that gets distributed from the pads onto the bodies of the bees that apparently does the trick. The moist surface of this sponge is due to the absorption of atmospheric moisture within the cluster by the glycerin humectant.

Practical application: Glycerin absorbs nearly half its weight in water at cluster humidity (which runs at about 50-60% independent of ambient humidity). My sons and I have learned to check for a pad’s potential for acid transfer from its surface by touching them lightly with a fingertip, and then tasting that finger for acidity [[14]]. So long as the pad’s surface remains moist and sour tasting, it can continue to disburse acid onto the bees.

Results

So how much total acid would the applied treatments contain? I weighed them as we prepared them to see (Table 2).

Table 2 The amounts shown in red are the total applied dose per hive. Note that at higher solvent (glycerin and water) ratios, less total acid is contained in the matrix. And the addition of water results in there being less glycerin as a humectant (and a drier surface).

So just how important is the total amount of acid in a pad or strip? This would be considered as the “dose per hive,” but doesn’t account for how much acid degradation occurs [[15]] or never gets dispersed before the pad is removed by the beekeeper or the bees (I’ve confirmed that oxalic acid degrades fairly rapidly when in contact with organic materials, but some matrices maintained substantial acidity (by the taste test) on their surface for over two months in my environment).

Although the total amount of OA contained in the matrix does not necessarily reflect the amount that makes it onto the bees, it did correlate with performance (Figure 12). The 1:1 sponges and NZ strips held the most acid (66 & 62 g respectively; both performed well), and the 1:2:1 King Zak cloth and chipboard the least (12 & 18 g respectively; both performed poorly).

Fig. 12 There appeared to be a weak correlation between the gross amount of oxalic acid in the pads or strips, and the resulting percent mite reduction. This could simply be because there was more acid on the surface upon application, or more of a reservoir of acid to diffuse to the surface over time. Note that the highest doses were no more efficacious than half the dose, notably with the sponges, KZ cloth, and corrugated cardboard — the matrix appeared to be more important than the dose! Surprisingly, the sponges with the 1:2:1 ratio performed very well in all test hives but two.

Update: It’s clear that it doesn’t require 50 grams of oxalic acid to obtain good efficacy.  The new product Varroxan contains 7 grams of OA dihydrate per strip, with 4 strips recommended per hive, which equals only 28 grams – a figure supported by the data above.

In my analyses, I used median values rather than means. Means can be greatly skewed by a single hive with a very high mite count. Medians more reflect what a beekeeper is interested in — the midpoint, with half the hives exhibiting lower, and half higher values. Statistically, one includes the standard deviation or a box plot. But with this large data set, I found that simply showing the raw data in blue and red tells us all we need to know [[16]](Figure 13).

Fig. 13 Results 65 days after application of the treatments. The more red per treatment group, the poorer the performance; the more blue the better. I highlighted the best performers in yellow.  But pay attention to the median mite reduction figures in the small boxes below each treatment.

Summary of my interpretation of the chart

Important note: The chart does not indicate “efficacy” of treatment, but only reduction (in most cases) from the starting count. In any hive in which its red column is no taller than its blue column, its mite infestation rate did not increase (in most cases it decreased). I stacked the columns in this chart for better visibility — if you see any blue at all, that colony’s mite count went down. Any column showing mostly blue would indicate high efficacy, but I could not calculate the value, since we didn’t have negative controls.

Formulations: As far as formulation, the 1:1 ratio performed the best overall (the most blue), with a few other surprise showings. Its consistent performance across a variety of matrices is telling.

Matrices: Unfortunately, chipboard laid flat was unimpressive, even at the repeated 1:1 ratio. However, when hung in the New Zealand strips, it performed well. Swedish sponges were the most consistent performers overall, followed closely by the New Zealand strips, double-corrugated cardboard (notably at the 1:1 ratio), and the surprise showing by the thin King Zak towels (other than with the 1:2:1 ratio). I did not test Maximizer pads [[17]], since they’ve performed very similarly to Swedish sponges in previous trials.

Repeating the application: Surprisingly, replacing the treatments at 30 days didn’t improve their performance for any test group other than the King Zak towels. I’m not clear on why the Kiwis think that it is of benefit with the hung strips.

The citric acid treatments: I didn’t show the results of the citric acid treatments, since at our spot monitoring at the trial midpoint, many of their mite counts were exploding, so we removed them from the trial and treated them with oxalic. Bummer, since I had high hopes for citric.

Discussion

Reduction vs. efficacy: This was a comparative trial of the matrices and formulations, in which we could compare the percent mite reductions by the various treatments, but not determine efficacy, which would have also required an untreated negative control group.

For example, if in a negative Control group the mite count quadruples over the two months of a trial (a realistic increase), a colony that maintained its original starting infestation rate would exhibit a percent mite reduction of zero, but an efficacy of 75% (relative to the Control) by the Henderson-Hilton calculation.

Practical application: Based upon the major increases in the infestation rates of the citric treatments and the other poor performers, we can conclude that the efficacies of most of the 1:1 treatment groups were actually quite high.

Another thing to notice in the chart is that you tend to see proportionally more red in colonies that started with low mite counts, compared to those that started with high mite counts. This is something that I’ve noticed before with other miticide treatments [[18]] – that you get your greatest amount of “treatment failures“ in colonies starting with lower counts. I’ve reworked the data in Figure 14 to show the pattern.

Fig. 14 Note that there are proportionally more increases in mite counts in those hives starting with lower counts (to the left) than in those with higher starting counts (to the right). I’m not clear as to why this is, but it was again apparent in this trial.

Practical application: Mite treatments in general tend to exhibit a greater percent reduction (and thus calculated efficacy) when applied to high-mite hives than to low-mite hives. I wish that I could explain why!

Musing on other studies

There are a number of really good studies on OAE, but I must take the results of a number of others with a grain of salt. Some do not understand that although the treatment causes elevated mite drop during the first week, that it may also cause an increase in the infestation rate for the first month, taking two full months to attain full efficacy (perhaps due to additional modes of action other than acute toxicity). And as shown above, it makes a difference whether the test colonies start with low or high mite infestation rates (so starting with low-count hives may result in more confounding outliers).

In addition, as evidenced by this trial:

• It’s not only about the total dose applied.
• The ratio of oxalic acid to glycerin makes a big difference.
• As does the delivery matrix used.
• The degree of saturation of the matrix (“sloppy” matrices may work better than “dry” ones).
• The amount of surface area of the of the pads or strips is critical.
• As well as is their placement — bees apparently must make contact in order to distribute the acid to the mites.
• The surprising observation that hung strips require a greater amount of surface area than do pads laid flat across the top bars (at least when applied to double brood chamber hives).
• Whether the surface of the delivery matrix remains moist and acidic.
• The fact that we’re not yet clear on the modes of action that oxalic treatment has upon the mites (it’s not just acute toxicity — watch this space!).
• And add the effect of the starting infestation rate, as well as
• The large differences in hive-to-hive performance in the same yard.

Confusing? Yes. Does OAE work? Yes. Do we still have a lot to learn? Yes!

Final Notes

The best use of this treatment appears to be application at the beginning of the honey flow. We need more research on its efficacy at other times of the season.

Repeated application of oxalic acid without rotation of miticides with other modes of action may well select for the evolution of resistant mites (don’t bet against evolution). Thymol is a great follow up after you’ve pulled your honey. Formic acid works well in the springtime. You can also rotate in Hopguard or a synthetic miticide. And of course our goal is to use resistant bee stock that may only require a single treatment a year!

A request: Please don’t write me for details on application until you’ve read this instructions page (which I will try to keep updated):

https://scientificbeekeeping.com/instructions-for-extended-release-oxalic-acid/

Acknowledgements

Thanks to my helpers Rose Pasetes, Brooke Molina, and Corrine Jones.

Citations and Notes

[1] https://scientificbeekeeping.com/instructions-for-extended-release-oxalic-acid/

[2] https://scientificbeekeeping.com/extended-release-oxalic-acid-progress-report-2/ (First published in American Bee Journal, October 2017)

https://scientificbeekeeping.com/extended-release-oxalic-acid-progress-report-3/ (First published in American Bee Journal, January 2018)https://scientificbeekeeping.com/extended-release-oxalic-acid-progress-report-4/ (First published in American Bee Journal, November 2018

https://scientificbeekeeping.com/extended-release-oxalic-acid-progress-report-2019/ (First published in American Bee Journal, December 2019)

https://scientificbeekeeping.com/2022-extended-release-oxalic-update-part-3/ (First published in American Bee Journal, May 2022)

https://scientificbeekeeping.com/testing-cotton-matrices-for-oae/ (First published in American Bee Journal, January 2023)

[3] Available on Amazon, or much cheaper if purchased in bulk lots of 500 or 1000 (contact Oliver Weiss oliver@ossipee.biz).

[4] https://beequip.nz/

[5] https://scientificbeekeeping.com/7701-2/  (First published in American Bee Journal, March 2022)

[6] Maggi, M, et al (2016). A new formulation of oxalic acid for Varroa destructor control applied in Apis mellifera colonies in the presence of brood. Apidologie 47: 596-605.

[7] Kanelis, D, et al (2023): Evaluation of oxalic acid with glycerin efficacy against Varroa destructor (Varroidae): a four year assay. Journal of Apicultural Research, DOI: 10.1080/00218839.2023.2169368

[8] https://scientificbeekeeping.com/extended-release-oxalic-acid-progress-report/ (First published in American Bee Journal, July 2017)

[9] Selective Breeding Progress Report 2023

[10] Pratt Eco Options, in a box from Home Depot. I’ve now tried a few brands, and none really hold together long.

[11] https://www.uline.com/Product/Detail/S-18997/Corrugated-Pads/8-1-2-x-11-Chipboard-Pads-050-thick

[12] From Amazon: “Eco Friendly Reusable Cleaning Cloths, Reusable Paper Towel Cloth, 30 Sheets, All Purpose Clothe, Biodegradable.” Thank you to the beekeeper who suggested these, and whose name I’ve misplaced.

[13] For the occasional weaker colony, we applied strips proportionally, in order to maintain consistent exposure.

[14] I of course am not recommending that you do this. But keep in mind that a single serving of spinach may contain a full gram of oxalic acid.

[15] These figures are the acid content immediately after preparation. I’ve not yet performed titrations to determine how rapidly the acid degrades after preparation (it’s on my to do list!).

[16] I know — without a calculated p-value, trusting our eyes and brain to pick out a pattern would never pass peer review. But I often trust my eyes more than I trust convoluted statistics.

[17] 2022 Extended-Release Oxalic Update Part 1 https://scientificbeekeeping.com/7701-2/ (First published in American Bee Journal, March 2022)

[18] https://scientificbeekeeping.com/mite-control-while-honey-is-on-the-hive-part-2/ (First published in American Bee Journal, December 2020)

The Status of Our Industry Regarding Varroa Management: Part 3– Reading the Fine Print

Contents

CATCH UP. 1

A LOOPHOLE?. 1

“THE LETTER”. 2

Authority to Regulate. 2

Unreasonable Adverse Effects on the Environment 2

Our Questions (again) 3

EPA’S RESPONSE. 4

WHERE WE NOW STAND. 4

Acknowledgements and clarification. 4

Citations and Notes 4

The Status of Our Industry Regarding Varroa Management

Part 3

Reading the Fine Print

First published in ABJ December 2023

Randy Oliver

ScientificBeekeeping.com

CATCH UP

In the July issue of this Journal, I wrote about the options (legally allowed or unapproved) available to U.S. beekeepers for varroa management, especially with regard to use of the “natural miticides” [[1]]. However, after having the Chief of the Biochemical Pesticides Branch summarily reject my request for EPA to consider granting beekeepers an Own Use Exemption for the organic acids and thymol, I went back and reread the text of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) more deeply.

Allow me to again state that I am by no means a lawyer, but I just wanted to make sure that I wasn’t missing anything. So I searched the text of FIFRA for terms such as “use,” “regulation,” “unlawful,” and “exemptions.” I read a lot of paragraphs and sections, but didn’t find anything of particular applicability to us, until I searched for the word “unregistered.” And bingo — it looked as though I might have found a loophole!

A LOOPHOLE?

Definition of terms: Section 2 of FIFRA states: “The term ‘‘pesticide’’ means (1) any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest.”

Practical application: This means that off-the-shelf oxalic or formic acids or thymol are magically turned into “unregistered pesticides” the moment that they are used with the intent to control varroa — so watch your thought bubble!

To my surprise, regarding the use of unregistered pesticides, (such as generic oxalic, formic, or thymol) I discovered that FIFRA does not mandate that the EPA regulate their use, but only that the Agency has an option to do so, based upon its determination that regulation would be necessary to prevent unreasonable risk. Aha, could this be an avenue worthy of pursuit?

So I decided to try my luck again, and carefully wrote a letter to the Chief, requesting clarification. By “carefully,” I mean that I refined draft after draft, since I figured that I’d only get one chance at getting a favorable answer.

“THE LETTER”

Here’s a copy of the letter:

Sent: Sunday, July 23, 2023 9:03 AM

Dear [Intentionally Withheld],

In a previous meeting, we beekeepers asked you about EPA granting beekeepers an own use exemption (similar to that in New Zealand’s [^a]) for application of generic substances such as formic and oxalic acids to their beehives. I now realize that we had asked you the wrong question — it is not up to the EPA to grant exemptions; according to Section 136a of FIFRA, such use is exempt by default.

Authority to Regulate

Section 136a states that “To the extent necessary to prevent unreasonable adverse effects on the environment, the Administrator may by regulation limit the distribution, sale, or use in any State of any pesticide that is not registered …” [boldface mine].

Note that Section 136a does not state that the Administrator shall regulate the use of any unregistered pesticide, but only that it may. As far as beekeepers are concerned, our interpretation is that FIFRA does not confer blanket authorization for the EPA to regulate or restrict the use of every off-the-shelf “natural” substance used for pesticidal purposes within beehives, but may limit the use only of those that it has determined would cause unreasonable adverse effects on the environment.

Such a decision to limit the use of a specific pesticide would need to be based upon a determination from a formal risk assessment by The Environmental Fate and Effects Division that such regulation is necessary to prevent unreasonable adverse effects on the environment.

So the questions that we beekeepers should have asked you are:

1. Whether the OPP has formally determined that it is necessary for the EPA to limit the use by beekeepers of unregistered, generic, off-the-shelf oxalic acid, formic acid, thymol, or food-grade plant oils for varroacidal purposes in their own hives, in order to prevent unreasonable adverse effects on the environment.
2. If so, has the EPA published their risk assessment to justify that decision and, where can we find that risk assessment to read?
3. And has the EPA decided to enforce action against such own use?

Unreasonable Adverse Effects on the Environment

The term “unreasonable adverse effects on the environment” means (1) any unreasonable risk to man or the environment, taking into account the economic, social, and environmental costs and benefits of the use of any pesticide, or (2) a human dietary risk from residues that result from a use of a pesticide in or on any food inconsistent with the standard under Section 346a of Title 21.

Regarding the use (as opposed to the advertisement or sale) of the generic off-the-shelf substances oxalic acid, formic acid, thymol, and food-grade plant oils by beekeepers for pesticidal purposes in their own beehives, we cannot imagine how EPA could have determined that own use of these substances would result in “unreasonable risk” to either man or the environment.

 Unreasonable risk to man (the applicator)

Similar to wood bleach, oven and toilet cleaners, and any number of off-the-shelf solvents, the above substances are commonly used by the public without unreasonable risk to the user. The minimal amount of injuries to beekeepers from using these substances in the U.S. and New Zealand (where such unregulated use is permitted) suggest that there is no unreasonable risk to the applicator.

Unreasonable risk to man (the public)

Since these natural products are already a part of the human diet and present in nature, and since all applications would be limited to the confines of wooden beehives, there is no unreasonable risk to the public. Not only that, but if beekeepers were to replace their current use of amitraz with these natural products, it would decrease the overall risk to the American public.

The economic benefit to the beekeeping industry

The few registered varroacides currently on the market are unreasonably expensive, often difficult to use, and with label directions that often do not reflect local climate and biological variations between individual honey bee colonies. The economic benefit to the beekeeping industry from being able to use these off-the-shelf natural products would be immense!

Unreasonable risk to the environment or off-target species

Since all these substances are naturally produced by plants or animals, are readily biodegradable, and applied only within the confines of bee hives, there is obviously no unreasonable risk to the environment. There would be no off-target species (other than the bees within that hive) exposed to the substance.

Unreasonable human dietary risk from residues

Since thymol, oxalic and formic acid already have exemptions from tolerance in honey, and since there is no restriction against adding food-grade aromatic plant oils to honey, application of these substances to beehives would not result in any unreasonable risk to the consumer.

Our Questions (again)

1. Has the OPP formally determined that it is necessary for the EPA to limit the use by beekeepers of unregistered, generic, off-the-shelf oxalic acid, formic acid, thymol, or food-grade plant oils for varroacidal purposes in their own hives, in order to prevent unreasonable adverse effects on the environment.
2. If so, has the EPA published their risk assessment to justify that decision and, where can we find that risk assessment to read?
3. And has the EPA decided to enforce action against such own use?

Our questions apply only to “own use” of the generic substances specified above. We understand that advertisement, distribution, or sale of these substances for pesticidal purposes requires registration and adherence to the instructions on the label.

Thank you for your time ― we look forward to your answers,

Randy Oliver

Footnote

[^a] (1) Schedule 2 of the ACVM (Exemptions and Prohibited Substances) Regulations 2011 provides for an exemption from registration under the ACVM Act referred to as the “own use” exemption. The exemption applies to a substance or compound prepared by a person for use on animals or plants that they own, or on any land, place or water that they own or occupy.

(2) In a beekeeping context, the ‘own use’ exemption is commonly used when a beekeeper prepares and applies preparations containing generic substances, such as oxalic acid or formic acid, to their own hives for control of varroa mites.

EPA’S RESPONSE

I received no response.

I brought this up with the leaders of our national organizations. We and our lobbyist had some Zooms, and both organizations decided to forward copies of my letter to EPA under their letterheads. In addition, we asked a couple of state legislators’ staffs to look into it.

To my great surprise, when I was at Apimondia in September, I got a call to join a Zoom with the Administrator of the EPA, along with the leaders of ABF and AHPA. My letter had apparently worked its way to the very top of the Agency. The meeting went very well, with the Administrator being very open to the situation that our industry is in with regard to options for varroa management. We were informed that the Agency had a team of its lawyers working on a response (and the next day I finally received an email formally acknowledging receipt of my letter).

WHERE WE NOW STAND

At the time of this writing (mid-October), we’ve still not received answers to the questions I asked in July.

Practical application: Of immediate applicability to beekeepers is that we’ve yet to receive an answer to the simple yes/no question “And has the EPA decided to enforce action against such own use?” The lack of an answer suggests that the EPA is still in the process of making a formal decision. That apparently means that we’d all been erroneously assuming that the EPA had determined (prior to my letter) that it was against the law for beekeepers to use unregistered oxalic, formic, or thymol in their hives with the intent to control mites.

So what can I say? The agricultural industry — of which we are part — is regulated by the EPA as to what we can use to manage pests and parasites. But at this point of time, we beekeepers have no idea as to whether EPA has determined that it is legal or not for us to use off-the-shelf generic “natural” products for the purpose of varroa control. Until we get clarification from the Agency, the answer remains up in the air …

Acknowledgements and Clarification

I’ve intentionally withheld some of the names of those involved in this discussion. I’ve got no beef with the EPA — every employee with whom I’ve been in contact appreciates our situation and has been very helpful — they are just doing their job in following the law as it is written. Ditto for those at the USDA who would rather remain anonymous. I do wish to credit the representatives of our industry who have helped me in this process — notably Charlie Linder, Dan Winter, Chris Hiatt, and our lobbyist Fran Boyd.

Citations and Notes

[1] https://scientificbeekeeping.com/the-status-of-our-industry-regarding-varroa-mgmt-and-what-can-we-do-about-it/