2012 Almond Pollination Update

2012 Almond Pollination Update

ScientificBeekeeping.com

First Published in ABJ in April 2012

Randy Oliver

Who woulda thunk, what with all the lousy weather last spring, widespread summer drought, the reports of massive queen failures, the disastrous honey crop, and the high winter losses of the past few years, that there would have been enough colonies for almond pollination this winter? But to most everyone’s surprise, there was!

It seems like a lifetime ago that I wrote my first article for ABJ–on the status of almond pollination, way back in 2007! I’m typing these words during the middle of almond bloom 2012, and just spent the day in the orchards tending to my hives. The bloom today is on strong, and the weather perfect, with several varieties simultaneously in bloom (Fig. 1), which augurs well for a good harvest.

Figure 1.  Almonds in bloom in the Central Valley last season.  The cool, damp weather extended the bloom for the longest duration in memory; both growers and beekeepers were surprised that a record crop was set!  For you trivia buffs, the average tree last year set 7,353 individual nuts (I have not personally confirmed that figure).

Back in 2007, there had been a sea change in the beekeeping industry, shifting from primarily being honey producers, to instead depending upon pollination rental income from a single crop in California. The Golden State is now host to a million out-of-state bee hives which come to celebrate Valentine’s Day in the almond orchards. These immigrant pollinators outnumber California hives two to one. They arrive by pickup truck, flatbeds, and semi trailers, bringing with them every new strain of pest and pathogen from the far corners of the country, do their job (paying taxes to California as of last year), and then leave.

The big question each winter since 2004/2005 is whether there will be enough colonies to fulfill the pollination demand, and just how much growers are willing to pay for those hives.

More trivia: it took about 1.5 million colonies of bees to pollinate 750,000 bearing acres of almond trees, producing nearly 2 billion pounds of nutmeats. That means that on average, every colony pollinated about 1333 lbs of nuts, and at a wholesale price of about $2/lb, each colony’s efforts contributed to a gross return to the grower of $2666.00! If we divide that value by the approximate number of bees in an 8-frame colony (14,000), that means that each individual bee, on average, pollinated 19¢ worth of nuts. And at a $150 per hive rental rate, each bee rented at 1¢ for a month’s wages.

Supply and Demand

The supply of bees this season for almonds just barely met demand—it was neither short nor long. This indicates that the supply and demand market worked perfectly. It also indicates that the current offered rental rates are likely something that both growers and beekeepers can bank on, provided that the growers keep planting new acreage, that the world continues to crave almond nutmeats, and that colony winter mortality doesn’t suddenly go up to 50% or drop back to the 5-10% that we enjoyed prior to our bees having to share their blood with the varroa mite.

Adam Smith’s “invisible hand of the market” is clearly working as expected. The pollination needs of the growers are being met, and beekeepers are receiving adequate monetary incentive to supply enough colonies to continue to meet the growers’ needs.

So how does this unregulated and inefficient market manage to work so well to reach equilibrium? It’s driven by the simple bidding of almond growers against each other for a service that beekeepers are willing to provide. The economic demand for hives is relatively “inelastic”—growers need bees in order to set a crop, independent of the price. But the important thing to keep in mind is that the beekeepers do not set the average price for pollination contracts—it’s impossible for us to rig prices, since there is no way to keep beekeepers from undercutting one another (otherwise, in this inelastic market, we’d all be charging $200 per hive). Rather, beekeepers respond to the price that growers offer and adjust the number of colonies that they run based upon the degree of profitability of hauling them to almonds. It’s up to the growers to offer enough incentive for beekeepers to ramp up their numbers.

Just prior to bloom each year, we see the extremes: if the supply of bees is “long,” desperate out-of-state beekeepers trying to recoup hauling costs for hives for which they couldn’t find placement will advertize them for as low as $80 (the lowest price that I heard of this year). On the other hand, should supply be short, growers desperate to fulfill the crop insurance requirement for placing two 6-frame colonies per acre (USDA 2010) will bid the price up to $200 per hive (happened last year). The funny thing is that the next season the growers only remember the lowest advertized price; conversely, the beekeepers all remember the highest! The reality is that those extreme last-minute prices paid for a few hives only represent a drop in the bucket, and have little to do with the setting of a fair price for the other 99% already in place.

So the market, after some oscillations in recent years, seems to have settled upon a figure of around $140-$160 per 8-frame colony, sometimes with bonuses for stronger hives. At this price, Dave Mendes may find it worth the cost and hassle to haul thousands of hives from Florida to California (and is even more attractive for me hauling them the mere 100 miles to the orchards that I pollinate).

Colony Collapse and the Price of Rentals

CCD has been a mixed blessing for beekeepers—it caused disastrous losses for some, but has also grabbed the public’s attention about the plight of bees and beekeepers. Such attention has made it a tiny bit easier for almond growers to swallow the incredible jump in pollination prices since 2004 (Fig. 2). But the good news for those growers is that by dint of hard work and ingenuity, beekeepers have generally managed to supply enough hives each year. Most of us long-time almond pollinators have good relations with our growers, and certainly do not feel that we are gouging them. I want my growers to get rich–so that they are able to pay me a sustainable price for my hives! It appears that an inflation-adjusted price of around $150 is sustainable.

A recent economic analysis of almond pollination prices (Rucker 2012) concludes:

“Based on media reports, attentive readers who have tracked the issue might infer that managed U.S. honey bee populations are nearly gone. Our examination of the operation of pollination markets leads us to conclude that beekeepers are savvy entrepreneurs who use their wealth of knowledge of the particular circumstances of time and place—acquired over their lifetimes of work—to adapt quickly to changing market conditions. Not only was there not a failure of bee-related markets, but they adapted quickly and effectively to the changes induced by the appearance of Colony Collapse Disorder.”

Figure 2.  Acres of bearing almond trees in California (left scale, in thousands) vs. pollination rental rate (right scale, in dollars).  Note that it wasn’t any sudden surge in demand that caused prices to skyrocket—it was due to the sudden relative shortage of bees. Sources: Doug Flohr (2011), USDA, NASS, California Field Office, by permission; Almond Board of California; 2012 estimate.

The abrupt rise in pollination rental rates from 2005-2008 was a supply and demand “adjustment.” Although increased acreage of bearing almond orchards indeed increased the demand somewhat, it certainly wasn’t the main cause for the abrupt increase in prices—that was due to lack of supply—the number of colonies available for rent. The California State Beekeepers survey estimated that the winter mortality rate in 2004/2005 doubled from the previous year’s 15 percent to 30 percent (Sumner 2006). The resulting shortage of bees caused prices to start climbing. Then in 2005/2006, “On the heels of the 2005 shortage, some almond growers wished to secure their bees early for 2006” (Mussen 2006), and things started to get exciting!

Up until that winter, the growers had been able to bluff the beekeepers into thinking that there was no way that they could possibly afford to pay another penny for hive rent. But then, anticipating another shortage, they suddenly they went into a bidding frenzy for the short supply of available bees, driving the price up to an unheard of $150. The growers had been forced to tip their hand, and we stunned beekeepers got a taste of what the growers were really willing and able to pay for bees. There was no turning back!

Increased Winter Mortality

That high winter mortality rate continued to persist through last year (it appears to have abated somewhat this season). As much as we’d like to blame it on a single cause, in reality there were a number of reasons. The high fall/winter losses for 2004/2005 and 2005/2006 can largely be attributed to the failure of miticides (and beekeeper management) to control varroa, and to poor late-summer forage in some regions (Mussen 2006). (We may see a return of major mite issues next fall if are unable to adjust to the unavailability of a current popular miticide).

Additionally, as I’m pointing out in my articles on Nosema ceranae, that parasite also likely started adding an additional degree of stress about that time. Plus, in 2005/2006, some operations (including my own) suffered from a serious epidemic of “corn-yellow EFB-like” sick brood and unusual sudden collapses. Then in 2006/2007 Dave Hackenberg became the industry spokesperson for the syndrome that came to be known as Colony Collapse Disorder.

Folk rushed to place their bets upon what caused CCD—blaming everything from cell phones or jet chemtrails, to genetically-modified crops or systemic pesticides, to previously unnamed viruses. Since CCD issues seem to be abating this year, a number of those suspects can likely be exonerated. What is important to keep in mind is that beekeepers, given enough economic incentive, figure out how to deal with things.

Rucker explains: “What should be understood is that the state of the honey bee population—numbers, vitality, and economic output—are the products of not just the impact of disease but also the economic decisions made by beekeepers and farmers.”

If beekeepers’ primary income is from almond pollination, then they are going to do whatever it takes to ramp up their numbers. As Sumner (2006) pointed out, many of those colonies are likely to be “unemployed” for the rest of the season, and must be maintained at considerable expense by trucking them to good forage if you can find it, or by costly supplemental feeding. Sumner predicted, “The result is that rather than receiving half or one third of their annual revenue from almonds, many commercial pollinators may now require almonds to cover most of their annual cost of colony maintenance. If this scenario develops as described, we may expect the pollination fee for almonds to remain high.” Sumner was clearly prophetic.

As you can see by the graph above, due to the infusion of additional money from the almond industry, the beekeeping industry quickly responded to the problem of 30% winter losses; by 2008/2009 pollination prices had restabilized, but at a considerably higher set point.

So let’s take a look at the various market forces involved, specifically the demand for bees, based upon the amount of bearing acreage, and the supply of bees, which is largely determined by the wholesale price of honey and the amount of winter mortality.

The Beekeepers’ Situation

When honey prices were low, and winter losses starting hitting 35%, beekeeping for many became unprofitable. The almond growers stepped up and threw the beekeepers a lifeline in the form of higher rental income from pollination. And for that we beekeepers should be immensely grateful. In the past two years I’ve even heard beekeepers saying that times now are pretty good—with both honey and pollination prices at historically high levels, they are actually making money (myself included).

And then comes this year, with a completely unexpected full supply of bees for almonds! CCD seems to have largely disappeared (which is why “Disappearing Disease” used to be called just that—the disease would spontaneously disappear). The question now is, will there be an excess supply of bees next season exerting downward pressure on rental rates?

A projected shortage of strong colonies is the main bargaining chip for beekeepers. But that doesn’t mean that lack of shortage is going to drive down pollination rates to any great extent, since the degree of supply directly reflects the return on investment to beekeepers. In order to maintain high colony numbers, commercial beekeepers today spend a fortune on trucking, queen replacement, medications, pollen supplements, and syrup; not to mention about twice as much labor per hive as back in the day.

A typical migratory pollinator nowadays may need to replace 50-70% of his colonies over the course of a season. The “three P’s”—pathogens, pesticides, and poor nutrition are a deadly combination to bee health, and the necessary crowding of hives exacerbates the problems.

The need to make up replacement colonies from splits eats into income that might have otherwise been made from the unsplit hives (Harmon 2011). And it’s much more expensive to try to build up your operation late in the season in time for almond pollination, than it would be to work instead with the normal honey bee seasonal cycle and split colonies on natural pollen flows in early spring (too late for almonds). So unless there’s enough reward in the almond orchards, it simply won’t be worth it for beekeepers to maintain the numbers of strong hives that the growers desire.

But there are always some beekeepers who for some danged reason or another just give their bees away in almonds! Beekeepers could learn from the almond industry. At a recent almond growers’ convention (Waycott 2012), Brian Ezell from Paramount Farms explained that:

• “Growers & Sellers must place value in what we produce. Buyers do not expect our industry to sell below the cost of production, but they will gladly let us!
• Growers must draw the line on acceptable grower returns. There is never a reason to sell any…almond below the cost of production.”

Beekeepers should take this sage advice to heart! Those who rent hives at less than the cost of production destabilize the market and hurt us all.

There is a term used in economics: the “marginal cost of production”–the cost of producing one more unit of a particular good. In the case of the supply of hives for almonds, that would be the cost to add one additional strong hive to the overall supply of bees (including the placement cost required to get them in and out of the orchard). In an expanding market, such as the demand for hives in almonds, the price paid by the buyer must allow the supplier to recoup his marginal cost of production.

So what’s the cost of production of a new hive? I don’t know how much it takes for the rest of you to produce an additional hive for almonds, but I figure over $200, so that fact alone suggests that colony rental rates won’t be dropping much.

But is it fair to compare the marginal cost of production to something that is merely rented out? Perhaps we should rather be looking at the “return on assets”—in the case of beekeepers, the question would be, is running an additional hive a good “investment”? Data from an informal survey by Dr. Eric Mussen (2009) suggested that at that time it cost a beekeeper about $180 to maintain an 8-frame hive for a year—and costs have gone nowhere but up since then. Granted, that hive, if well managed and if the weather cooperates, may return some income from honey or other pollination contracts, but many beekeepers base their colony count upon a break-even in almonds. So if a temporary glut of hives occurs, my guess is that the supply will quickly adjust downward the next year.

There is also the “reserve pool” of potential hives that are not normally brought to almond pollination (these are akin to the “carryout” reserve of commodity crops). These hives belong to honey producers who simply don’t find the price offered for almond contracts to be worth the time, trouble, cost, and risk to haul them to California. This reserve acts as a stabilizing force for the market price—should the growers suddenly get desperate due to a major shortage and start offering $200, then that would be enough motivation for some of those reserve hives to get put onto trucks. Conversely, if the offered bid dropped to only $100, even more hives would pass on almond pollination, and instead spend the winter resting (along with their owners).

Bottom line: the number of colonies available for rent reflects the degree of profitability to the beekeeper. Both the marginal cost of production and the return on assets suggest that the sustainable price for almond rental fees for 8-frame colonies will remain at around the current price, and adjust upward for inflation.

The Growers’ Situation

The cost of production for almonds is currently approaching $4000 per acre if you calculate it by the book (Klonsky 2011, 2011), although that high theoretical cost should be taken with a grain of salt. Renting two hives per acre at $140/hive accounts for about 7% of theoretical production costs—in the same ballpark as either irrigation or fertilizer.

However, grower return per acre is pretty good–at last year’s average yield per acre of 2600 lbs and the current farm gate price for nut meats of about $2 per lb, the average grower enjoys a net return of $1200/acre (over total operating costs), or $2700/acre (over cash operating costs, excluding land and trees) (Klonsky 2011). When you take into consideration that the grower would lose money on every acre without bees, it’s easy to see why they are (begrudgingly) willing to pay $150 or more for colony rent (of course growers begrudged paying me $12/hive when I first began pollinating, and have begrudged every price increase since).

So what does the crystal ball say about future demand for colonies in almonds?

Projected Acreage

A recent presentation to growers on the economics of almond production (Harp 2011) projected that the world demand for almonds will require about 30–40,000 additional bearing acres in California per year, which in turn will require an additional 60–80,000 8-frame colonies. This projected additional demand should help to support pollination prices.

Sure there’s some concern about the new “self-fertile” cultivars decreasing the demand for bees, but those varieties still require at least a colony per acre to be cost effective (Northcutt 2011), so no one is expecting them to make much of an impact for the foreseeable future.

Stocking Rate

The thing that I can’t understand is why some growers shoot themselves in the foot by shorting themselves on bees. I picked up a new contract this season—a beautiful, by-the-book 15-yr orchard that yielded less than 2000 lbs/acre. But the grower had only been contracting for one 7-frame colony per acre, figuring that his neighbor rented enough bees to cover one end of his orchard (adjacent growers consider this sort of getting a free ride akin to thievery).

When I began pollinating almonds, growers rented two hives of bees per acre and were happy to obtain 1000 lbs of harvested nutmeats per acre. Today, state-of-the-art orchards harvest 4000 or more pounds from the same acre! Four times as much yield means that four times as many nuts are set per acre, meaning that at least four times as many blossoms must be pollinated per acre. Yet the average hive stocking rate is still set at only two hives per acre, even though average colony strength hasn’t substantially changed (Sheesley 1970). Honey bee foraging behavior hasn’t changed, so I wonder if we are expecting today’s bee to do four times as much work as yesterday’s bee?

Recent research by Dr. Frank Eischen indicates that at peak bloom of early cultivars, there was much better nut set at 2 colonies per acre compared to 1 colony; and for late cultivars better at 1 colony/acre as compared to 0.77 (which is the range that the grower in the test was willing to allow). His findings strongly suggest that growers are seriously not renting enough bees per acre to realize the full potential nut set.

Practical application: Dr. Eischen’s findings strongly suggest that growers are not contracting for enough bees per acre in order to realize the full potential nut set, especially in the newer high-density orchards and for the densely-flowering hardshell cultivars. As growers get educated to this fact the demand for bees should increase.

At the U.C. experimental almond research station that I’ve pollinated for over 25 years (Fig. 4), the average bee stocking rate has been 18–20 frames of bees per acre of mature trees, or the equivalent of two 9–10 frame colonies. But you don’t have to guess as to whether the stocking rate for any particular orchard is adequate—it’s easy to check for yourself! In a fully-stocked orchard, the bees will have completely stripped the pollen from the blossoms by early afternoon each day (Fig. 3).

Practical application: I suggest to my growers that they confirm that they are getting optimum pollination by checking the blossoms for pollen in the afternoon at peak bloom.

Figure 3.  Early bloom on a cold morning in Arbuckle this spring.  My son Ian at work in the background; our bees at work in the foreground.  Note that the pollen has not yet been stripped from these blossoms.  At full bloom, recent data from Dr. Eischen suggest that growers may not be renting enough colonies per acre.

Without adequate pollination, the grower may forego some portion of the potential yield of that orchard. Smart growers go ahead and contract for bees a bit on the heavy side as a form of risk management should the weather not cooperate—in an orchard heavily stocked with bees, a good crop can be set during brief breaks in the weather.

Practical application: stocking an adequate amount of strong colonies per acre is an effective form of risk management for growers should poor pollination weather occur during bloom.

Although growers balk at spending more on hive rental, they should do the math! Say that an orchard is yielding 2000 lbs at two hives per acre. It follows that with nutmeats selling at $2 a pound, an increased yield of merely 4% would easily pay for an additional hive at $140. Dr. Eischen’s data suggest that growers may be missing out on far larger percentages of yield than that! I just don’t understand why a grower who has invested some $2500 in fixed costs per acre would short himself on bees at the most critical time for nut set!

Practical application: the beekeeping industry is doing a poor job at educating growers as to optimal stocking densities. If we were to invest some money into research and grower education, both parties would benefit!

Figure 4.  At the Nickels Soil Laboratory in Arbuckle, U.C. researchers experiment with every combination of rootstocks and almond cultivars, planting density, type of pruning, methods of irrigation, fertilization, etc.  I’ve been pollinating this orchard long enough to see plots get planted, the trees grow to maturity, and then be ripped out and the plot replanted!

Every spring I speak with grad students at the Nickels Lab who are marking off individual blossoms, monitoring soil probes, etc. Such research has allowed growers to increase production from 1000 lbs to an average 2600 lbs per acre, with 4000+ lbs expected in the near future! The research station is self-sustaining—they make enough from the sales of harvested almonds to cover their costs and pay the staff. Would I be frivolous to suggest that some of our bee research stations follow a similar model?

Frame Strength

The question often arises, what is the most efficient colony strength for almond pollination hives? And furthermore, what is a 10-frame colony worth relative to 4-framer, as far as the actual amount of pollination work that gets done?

There are plenty of opinions based upon what someone thinks, but not a whole lot of firm data. In my 2007 article, I plotted out a graph derived from a bunch of unpublished UC Davis data. It suggested that the relationship between frame strength (from 4 to 16 frames of bees) and actual pollination work was directly proportional—i.e., that a 12-frame colony would do as much work as three 4-framers. Of course, nearly everyone was incredulous.

So I found the best published data sets to date—a large 1970 study of 256 colonies, and a meticulous 2007 study of 83 colonies. Both studies used the amount of pollen removed by a pollen trap as a proxy for the number of blossoms visited by the foragers of that colony. One may argue fine points, but shy of netting off acres of almonds, the amount of trapped pollen is probably a fairly reliable indicator of pollination performance.

I reworked the data —setting the amount of pollen trapped by 4-frame colonies as the baseline to which pollen collection by colonies of other strengths could be compared. In the graph below (Fig. 5), I set the amount of pollen collected by 4-framers at 100%; if a larger colony collected three times that amount, then it would be rated at 300%. Interpretation tip: If there were indeed an optimal colony size, the bars would form a curve, peaking at that strength.

Figure 5. Pollen collection as a function of colony frame strength, relative to that of 4-framers.  The green line is the hypothetical relationship that pollen collection is directly proportional to frame strength, rather than being more efficient at any particular colony size.  And that is pretty much what the actual data indicates over the range from 3 –16 frames!  These hard data sets indicate that a single 12-frame hive is likely worth at least as much to the grower as three 4-framers!   Data reworked from Sheesley and Poduska (1970), 256 colonies, five orchards, two years combined data; and Eischen (2007), 83 colonies.

The above findings will come as a surprise to those of us (including myself) who assumed that stronger colonies would have a greater percentage of field bees, and would thus be relatively more effective pollinators per frame of bees. The data also suggest that pollination value continues to increase linearly clear up to at least 16 frame strength! By rights, then, if 4-frame colonies are renting for $100, then a 16-framer should rent for $400. That’s going to be a hard sell, no matter how robust the data!

Practical application: again, unless beekeepers educate growers with firm economic data, we may not be paid fairly for strong colonies.

OK, you say, but strong colonies, due to their larger cluster size, must certainly fly better earlier in the morning or in cool weather! Luckily, Dr. Eischen also collected data comparing the number of returning pollen-carrying foragers in morning and evening, which I also reworked. In addition, I included his calculations for the number of grams of pollen trapped per frame of bees. To interpret the graph below (Fig. 6), for each color of bars, look to see if there is a curve indicating an optimal colony size for pollination efficiency.

Figure 6.  Eischen’s 2007 data, reworked.  I divided both returning pollen forager rate and pollen collected per day by average colony frame strength during bloom in order to get pollination rates per frame of bees.  Surprisingly again, the per-bee morning and afternoon foraging rates were highest for the 7-framers.  On the other hand, the highest rate of actual pollen collection (as measured by pollen traps) was by the 10-frame colonies.

Well, more surprises again—it appears that a larger proportion of bees in the smaller colonies actually foraged for pollen! Lots of us would have lost money on that bet, but I put a great deal of faith in any of Dr. Eischen’s well designed and meticulous studies (Fig. 7)! The astute reader may have noticed that the two graphs have different bottom axes. In the first graph, pollen collection was plotted against initial field grading, rounded to the nearest frame at the beginning of bloom. In the second graph, I plotted it against the more accurate average of actual measured frame strength over the entire course of bloom. I did this since not all of the colonies in the study grew in strength during the bloom.

Bottom line: it looks like a frame of bees performs approximately the frame amount of pollination work regardless of the size of the colony, suggesting that two 4-framers would provide about as much pollination service as a single 8-framer. If anything, pollination efficiency appears to be greatest in 8- to 12-frame colonies, which comes as no surprise, as this is around the size at which a colony is typically feeding the greatest proportion of brood.

Practical application: the implications of the above data sets are that growers are either paying far too much for 4-frame colonies, or far too little for 12-framers (I personally favor the latter interpretation).

Figure 7.  Dr. Frank Eischen of the USDA ARS at work in the almonds this season—preparing to net off a branch to measure bee pollination rates.  The bee industry owes Dr. Eischen a debt of gratitude for his valuable practical research on mite control, Small Hive Beetle, and almond pollination.  Photo courtesy Kodua Galieti, whose images can be seen at koduaphotography.com.

And even those growers who are paying bonuses for stronger colonies may not be compensating beekeepers adequately. I had the choice this year between several different contracts (Table 1):

Table 1. Comparison of payment per frame of bees, depending upon the contract. Note that in the current market, the beekeeper really has little incentive to produce strong colonies. Other than saving a bit on trucking, you get paid more per bee the weaker the colony!

Traditionally, it used to be worth it to me to combine my 4-framers with my 8-framers, and contract for 12-frame colonies at a premium price (thus saving on trucking). There is no longer much incentive for me to do so, since the current market rewards the beekeeper for the number of boxes, rather than for the numbers of bees in those boxes.

So some beekeepers stick to the “Domino’s Pizza model”—forget busting your butt to produce premium colonies that growers aren’t willing to pay proportionately more for. Rather, offer them the minimum quality that they’ll accept, for what appears to be a cheap price. After all, they are only screwing themselves!

Grower Education

I hope that Dr. Gordon Wardell, who has been collecting data on nut yield vs. average colony frame strength, will be able to share those important economic figures with the industry some day (hint, hint). My suggestion to the almond growers would be to shift from renting numbers of hives to numbers of frames of bees per acre.

To that end, I drew up a new contract this year for one of my more enlightened growers: I guaranteed a specific number of frames per acre (18), independent of the number of hives that I used to fill the contract. For validation, I invited my grower to inspect as many drops as he wished with me, to ensure that I met the guarantee. This contract allowed me great latitude as to how to fill each drop, and could easily have had a proportional penalty written in for failure to reach the target. Since I came up a little short on hives in February, I ran all my 12-framers to this contract, and then cleaned up by renting all my weaker hives at a high per-frame rate to other growers.

Such a contract may become a model for the future. But for now, there is unfortunately a disproportionately low return for providing extra-strong colonies, and I’m tired of all the feeding and work necessary to produce them!

Fungicides

Almonds are susceptible to a variety of fungal diseases, especially in the Central and North Valleys, which receive more rain than down south. Following wet weather, the sounds of tractor-mounted blowers, crop-duster biplanes, and helicopters are common in the orchards, spraying right over our hives (Fig. 8). Although such fungicides are touted as being harmless to bees, after a spray we may observe entombed pollen, brood issues, and adult bee dwindling.

Figure 8.  I snapped this photo of John Miller’s hives as they were being thoroughly fogged with fungicide in the middle of the day.  Although fungicides do not normally cause significant overt adult bee mortality, the surfactant adjuvants in the tank mix sure can!  Such spraying may also cause negative effects upon brood, beebread fermentation, and overall colony health.  Growers can mitigate these problems somewhat by spraying after dusk.

Of special concern to the California queen breeders are the queen cell losses that some see when raising queens from colonies that had been exposed to the fungicide PristineÒ. Dr. Gloria Degrandi-Hoffman of the Tucson Bee Lab recently presented the results of their research, which found negative effects from Pristine upon queen production.

On the other hand, I’ve seen legitimate research by BASF, the manufacturer of Pristine, which indicates that the active ingredient has little effect upon bee brood. At the last California Queen Breeders meeting, representatives from BASF, to their great credit, pledged to work with us to get to the root of the reported problems. The company has stationed Dr. Christof Schneider, one of their bee specialists from Germany, in California to monitor pesticide levels in pollen and to run studies in almonds. I applaud this sort of cooperative work between beekeepers and the chemical industry!

Some researchers have suggested that the problem may be due to pesticide synergies or surfactants added to the tank mixes. I also suggested that we should consider that no researchers have investigated whether there are synergies between the toxic amygdalin in almond pollen and common pesticides.

Eco-Terrorism in the Valley

As if you didn’t already have enough things to worry about, this January right in the heart of almond country, animal rights extremists perpetrated an act of terrorism by using kerosene and digital timers to incinerate fourteen parked cattle trucks at a major feedlot [1, 2]. Such destruction is a tactic used by those who feel that “Arson, property destruction, burglary and theft are ‘acceptable crimes’ when used for the animal cause” [2a].

What has the above got to do with beekeepers? Well, if you didn’t already know, “bees are abused and exploited for their honey, wax and other derivatives” [3]. There is “cruelty in the honey industry” [4]. “Many people who understand the cruelty involved in factory farming and are morally opposed to eating meat find it less obvious that the lowly honeybee should also be of ethical concern…Like all factory farming, beekeeping has morphed into an industrial process which puts profits ahead of animal concerns” [5].

Your beekeeping operation could be the next target of some extremist!

One of the problems of the blogosphere is that folk concerned about legitimate issues can, by stretching the truth just a wee bit, incite those itching to destroy something to do so for some ostensibly “just cause.” The destruction of Harris Farms’ trucks should serve as a warning to all beekeepers that there are those out there who are under the impression that we abuse our bees–“Like other factory-farmed animals, honeybees are victims of unnatural living conditions, genetic manipulation, and stressful transportation” [6].

The press coverage of CCD has opened an opportunity for some to blame commercial beekeeping practices as the cause of death of our unfortunate charges. I am surprised by the number of blogs on the web by well-meaning folk who earnestly believe that, “There honestly is no escaping the harsh realities of methods within the commercial honey production process and the cruelty the bees themselves are forced to endure during such times” [7].

I read this after my sons and I had worked in the rain for a week to feed thousands of dollars worth of carefully-prepared and nutritious pollen supplement to my hungry hives, gently brushing the bees aside so that we didn’t squash them. Heck, in this instance, I literally treated my bees better than my own children! (Fig. 9). But you’d never know it if your only source of information was the Internet!

Figure 9.  My sons feeding pollen supplement to hungry colonies in the rain prior to moving to almonds.  We use a pine bough to “tickle” the bees so that they move down between the frames.  Some of my recent research strongly suggests that you don’t want to squash bees when you’re feeding pollen supplement (more later)!

Practical application: it’s up to beekeepers to educate the public as to the truth about how much we care for our bees’ well-being, and that we only make a living if we treat them well!

The Future

The reality is this: almond growers are doing pretty well these days. The projected world demand for tree nuts is strong, and almonds are the cheapest and most versatile among them. Indeed, one of the industry concerns is that sales of nuts are so strong that packers are having trouble maintaining a comfortable “carryout”—a minimum inventory to act as a cushion should there be a short crop!

California holds a virtual monopoly on world production of almonds, so long as our water holds out (there is no snowpack in the Sierra this winter). And the world loves almonds! They are not only a tasty confection, but also good for you.

Despite some record almond crops in recent years, prices to growers remain profitable. Grower Bill Harp (2011), speaking to the Almond Board, reports that projected 10-20% grower returns on assets are possible with the expected almond supply and demand fundamentals (this is in an economy where any return on assets is a good thing). The bee industry will continue to hitch a ride on that wagon.

Bottom line: The near future looks pretty rosy for both almond growers and beekeepers.

Good Sources of Information

You can track the weather and progress of bloom at the Blue Diamond website http://www.bluediamond.com/applications/in-the-field/index.cfm?navid=101).

Project Apism http://projectapism.org has two great webpages of interest to almond pollinators:

The Cummings Report http://projectapism.org/content/view/64/49/ written by almond grower and industry insider Dan Cummings, and the

Bee Status Report http://projectapism.org/content/view/93/49/

Your $1 per hive donation to Project Apism will help to support beekeeper-funded practical research.

Hilltop Ranch posts almond updates at http://www.hilltopranch.com/2012/02/almond-update-25/

References

Carman, Hoy (2011) The estimated impact of bee colony collapse disorder on almond pollination fees. ARE Update 14(5): 9-11.

Eischen, FA, RH Graham, R Rivera & J Traynor (2007) The effect of colony size and composition on almond pollen collection. http://projectapism.org/component/option,com_docman/task,doc_download/gid,40/Itemid,44/

Flohr, D (2011) 2011 Almond Forecast http://www.hilltopranch.com/wp-content/uploads/2011/05/almond-industry-historical-data-from-nass.pdf

Harp, B, et al (2011) Economics of Almond Production. (Broken Link!) http://www.almondboard.com/Handlers/Documents/Economics%20of%20Almond%20Production.pdf

Klonsky, KA, et al (2011) Sample costs to establish an orchard and produce almonds (flood). http://coststudies.ucdavis.edu/files/AlmondFloodVN2011.pdf

Klonsky, KA, et al (2011) Sample costs to establish an orchard and produce almonds (microsprinkler). http://coststudies.ucdavis.edu/files/AlmondSprinkleVN2011.pdf

Ludwig, G (2009) Present & Future Beekeeping: “Almonds” http://www.usda.gov/oce/forum/2009_Speeches/Presentations/Ludwig.pdf

Mussen, EC (2006) Chaotic almond pollination. (Broken Link!) http://entomology.ucdavis.edu/faculty/mussen/JanFeb2006.pdf

Mussen, EC (2009) How much does it cost to keep commercial honey bee colonies going in California? http://projectapism.org/content/view/83/27/

Northcutt, G (2011) Quest continues for self-fertile almond varieties. Tree Nut Farm Press 3(5).

Rabobank 2011 https://www.rabobankamerica.com/content/documents/news/2011/us_tree_nut_sales_to_remain_strong_in_coming_years.pdf

Rucker, RR & WN Thurman (2012) Colony collapse disorder: The market response to bee disease. http://www.perc.org/files/ps50.pdf

Rucker, RR, WT Thurmon and Michael Burgett (2011) Colony collapse: The economic consequences of bee disease. http://economics.clemson.edu/files/ccd-paper-full-package-apr14-2011.pdf

Sheesley, B and B Poduska (1970) strong honeybee colonies prove value in almond pollination. California Agriculture. August 1970: 4-6.

Sumner, DA and H Boriss (2006) Bee-conomics and the Leap in Pollination Fees. http://aic.ucdavis.edu/research1/bee-conomics.pdf

USDA (2010) Federal crop insurance corporation adjustment standards product administration and standards division handbook 2012 and succeeding crop years. http://www.rma.usda.gov/handbooks/25000/2012/12_25020-1h.pdf

Waycott, R, moderator (2012) The Economics of Growing Almonds. (Broken Link!) http://www.almondboard.com/Growers/Documents/The%20Economics%20of%20Growing%20Almonds.pdf

[1] (Broken Link!) http://www.fresnobee.com/2012/01/10/2677557/animal-rights-activists-take-credit.html

[2] http://www.animalliberationpressoffice.org/communiques/2012/2012-01-10_harrisranch.htm

[2a] http://activistcash.com/biography.cfm/b/1459-alex-pacheco

[3] (Broken Link!) http://www.think-differently-about-sheep.com/Animal-Rights-Bees.htm

[5] http://prime.peta.org/2009/01/but-what-about-honey-is-it-cruelty-free

[4] http://www.veganpeace.com/animal_cruelty/honey.htm

[7] http://veglin.hubpages.com/hub/Why-Honey-REALLY-isnt-Vegan

[6] http://www.peta.org/issues/animals-used-for-food/honey-from-factory-farmed-bees.aspx

Sick Bees – Part 17b: Nosema – The Smoldering Epidemic

Sick Bees 17: Nosema

The Smoldering Epidemic

Part B

First published in ABJ April 2012

Randy Oliver

ScientificBeekeeping.com

The Scientific Method

Effect of the Invasion

Why Would Nosema ceranae Not Cause Problems?

Understanding Nosema

Understanding the Honey Bee Superorganism

Energy and Protein Metabolism

References

You may have noticed that I’m doing a sort of “about face” in my assessment of the impact of Nosema ceranae upon colony health. I feel that I owe the reader an explanation. I just get this nagging feeling that there’s more to the invasion of this new parasite into the U.S. bee population than meets the eye. To truly understand the potential impact of nosema, we must look beyond its effects upon individual bees, and rather focus on its impact upon the superorganism that we call the honey bee colony.

The Scientific Method

Science is not about microscopes and laboratories (that’s technology); it is about the thought process that we use to make sense of our observations of the world around us. One can think in a scientific manner just as well while wearing dirty white coveralls as when wearing a clean white lab coat!

The true scientist holds no positions, frees himself of beliefs, and avoids any prejudices or biases. His only firm conviction is to remain completely open minded and objective in the never ending quest to understand why things are the way they are.

Science is based upon the free sharing of data (accurate observations) and its interpretation. Not every scientist will interpret the data in the same way. So long as good scientific method is followed, there is nothing wrong with floating highly controversial interpretations, and indeed good scientists relish having an established paradigm challenged.

As an aside, please realize that the editorial filtration process of scientific publication is hardly perfect. I’m personally sometimes dismayed by the poor quality of peer review of late, and have serious criticisms of both the methodology and interpretation in a number of recently published papers.

Warning: unless you are willing to research more deeply, I caution you to take any new scientific findings that get splashed across the headlines with a grain of salt, especially when “hot” topics, such as CCD, pesticides, the environment, or human health are involved!

(Back to the Scientific Method): any new interpretation as to why something is the way it is, or works the way it does, is subject to testing by proposing a “falsifiable” hypothesis. You can’t scientifically prove that anything is true (or that anything is “safe”); you can only “disprove” a hypothesis (such as that something does not cause measureable harm) by putting it to actual test in a well-designed experiment.

The best that you can do toward seeking truth is to find that the results of multiple experiments “support” your hypothesis. When a hypothesis has eventually been supported by enough robust data, then it is accepted as a scientific “theory”—a word that has much stronger meaning in science than it does in the common vernacular. A scientific theory becomes the paradigm by which the scientific community “understands” things—and is of course subject to revision should any new data come to light that falsify it.

When Dr. Mariano Higes found that Nosema ceranae was highly associated with the collapsing colonies that he observed in Spain, he proposed the hypothesis that the parasite was the cause. He further tested that hypothesis in various experiments by inoculating healthy colonies with spores, applying fumagillin or not, and then tracking the buildup of nosema and colony strength. He found that his results supported his hypothesis.

Other researchers, including myself, at first also found his hypothesis to be attractively plausible—it appeared to reflect the typical high mortality associated with the invasion of a naive host population by a novel parasite. However, when we sought to replicate Dr. Higes’ results in our own bees, we simply didn’t see a compelling cause and effect relationship, and as a result then questioned the validity of his hypothesis.

I myself fell into the skeptical camp; but I go out of my way to truly understand alternative viewpoints; to that end I have maintained a friendly ongoing conversation with Dr. Higes for the past five years—constantly challenging and questioning him. Such frank discussions are the best method to arrive at the actual truth of matters.

I want to be clear at this point that in this series I’m doing a lot of thinking aloud. I will try to be clear as to which conclusions (always subject to reevaluation) are based upon hard data and actual experimental testing; and which ideas or opinions are inferential—based upon suggestive data or observations. I also want to emphatically state that the evidence to date does not suggest to me that Nosema ceranae is directly responsible for either CCD or major colony losses; but it does appear to often be associated with them, and may be a contributor in some way. I’ll return to the subject of colony collapse in a later article.

Effect of the Invasion

So, how can we tell if the invasion by Nosema ceranae is having any substantial negative effect upon the health of our colonies? N. ceranae invaded East Coast apiaries as early as the mid 1980’s without anyone even noticing it, until it was discovered twenty years later by researchers investigating CCD. But then again, it was discovered in colonies suffering from CCD, which may be a telling point!

The effects of infection by the new nosema seem, in general, pretty similar to those of its cousin, although it appears to cause somewhat more gut damage, and may be a bit more resistant to fumagillin. The most notable aspect that is different about N. ceranae is that it apparently “has better mechanisms to evade host immunity to allow for faster growth and reproductive capacity than N. apis” (Chen 2009). Antúnez (2009) found that it up- and down regulates bee immune response genes differently than its cousin. Plus it is able to thrive over a wider range of temperature (Martín-Hernández 2009), so it exerts its negative influence over a more prolonged period each year. I suspect that it also has better mechanisms for transmission from bee to bee. All the above differences make it a more virulent pathogen –in the sense that it reproduces more efficiently, rather than necessarily causing increased individual bee or colony mortality.

Then Again, Why Would Nosema ceranae Not Cause Problems?

With the majority of U.S. bee samples currently being infected by nosema (presumably Nosema ceranae), it seems to me that perhaps the question that we should be asking ourselves is, “Why wouldn’t we expect this level of infection to be causing problems?”

There is a vast body of “classical” research on the fundamental negative effects of Nosema apis infection upon colony health and productivity. Nosema is an age-old nemesis of beekeepers. Why would we not expect similar effects due to the new nosema, which is even more successful at infecting bees?

Understanding Nosema

Nosema is adapted to turn a bee into a spore-producing factory; there is no benefit to the parasite in killing the bee. And therein lays the problem, because it makes nosema so insidious and unnoticeable. But a widespread increase in the prevalence of such an insidious infection could still exert major effects upon colony buildup, production, and survival.

Understanding the Honey Bee Superorganism

In order to understand the effect of nosema upon the colony, one must stop thinking of the honey bee as merely an insect. Rather, we must think of it at the level of the superorganism, similar to an intelligent, warm-blooded, fast-growing ten-pound animal. But not just any animal; specifically one whose rapid growth makes it ravenous for energy and protein—exactly the precious commodities that nosema steals from the colony.

So I did some research on the effects of gut parasites upon other animals. In humans, microsporidian infection of the gut results in malabsorption of nutrients (Kotler 1999). It is no surprise that a common result of gut parasitism is reduced growth rate and poor energy metabolism, due to less efficient digestion and utilization of food rations (McRae 1993). This made me think that I should compare the normal growth rate of the honey bee colony to that of other livestock. So I looked for a similar-sized, exceptionally fast-growing organism. I arrived at the modern day broiler chicken.

When I ran a farm store some thirty years ago, a broiler took 19 weeks to grow from egg to slaughter. Today, with better rations and breeds selected for rapid growth, it only takes about six weeks to grow the same chicken! As with the bee, this incredibly rapid growth rate requires a high energy, high protein diet, which must be optimally digested and utilized.

Next I downloaded data for the growth rate of a broiler, and transformed it into graphical form (Fig. 1).

Figure 1.  The growth rate of a modern broiler chicken.  The chicken grows from 2 lbs to 7 lbs in 36 days.  For perspective, the growth slope for a normal 12-month-old human child would appear dead level on the scale of this chart.  Data from Jacob 2011, CDC 2012.

Since the chicken’s weight crosses the 2-lb line early in this graph, we can handily compare its growth rate to that of a small colony of bees—a freshly-hived 2-lb package. In the following chart, I took data from two studies that measured package bee growth over time, and overlaid them on top of the chicken growth plot.

Figure 2.  Comparison between the weight gain of package bees vs. that of a broiler chicken.  The red curve shows how a package loses population until the first brood emerges.  After that point, packages grow considerably faster than even the fastest-growing chicken!  If our human child were to grow as rapidly as a bee colony, its weight would increase from 24 lbs to 250 lbs in the two months following its first birthday!  Data for 3-lb packages calculated from Nolan (1932) and Harris (2008),

Clearly, a bee colony grows at an amazing rate. But that ain’t the half of it! The chicken has the immense advantages of being penned in a warm room and provided with optimally-formulated chow, and maintains a compact body size, insulated by feathers. On the other hand, the industrious bee colony has to forage over a dozen square miles, spending a tremendous amount of energy in the process, as well as wasting a vast amount of body heat to the environment.

But I’m not done yet! If the chicken manages to store any excess energy or protein, it puts it on as fat or muscle—which then adds to its body weight. The analogous storage “tissues” of the bee colony would be the honey and beebread accumulated in the combs, but the above graph doesn’t reflect this fact. So let’s adjust the graph to take into account the bees’ stores (Fig. 3).

Figure 3.  Total weight gain (including honey and beebread) of a 3-lb package installed two weeks before the main flow, compared to the gain in body mass alone of bees or a broiler chicken.  When we measure total colony weight gain, the bees leave the broiler in the dust!  The end points of the dotted line are actual data Munro (1926); I estimated the intermediate curve based upon measurements by Nolan.

By the end of the above chart, the broiler was essentially done growing. On the other hand, the colony was approaching its maximum population, but it was hardly done “growing.” In the next two months, it gained yet another 218 pounds! It is not unheard of for a colony with a bee body mass of 12 lbs to gather, process, and stockpile its body weight in surplus honey each day!

So what’s my point? It’s that we beekeepers expect our bees to perform a feat of rapid growth beyond the capability of perhaps any other animal! But the bee superorganism can only pull this prodigious feat off by being extremely efficient at digesting and utilizing protein and sugar (energy). That is why it is completely dependent upon two of the richest foods in nature—pollen and nectar. A bee colony would starve to death on the sorts of diets that most organisms are adapted to.

A strong, foraging colony during spring or early summer must consume and efficiently process, every single week, a minimum of 2-3 pounds of high-protein pollen plus several (about 10-15) pounds of sugar. By comparison, a rapidly-growing chicken eats only about 2-3 lbs. of total dry ration; a similar sized growing cat eats only about a pound of dry chow a week.

The point: The goal of a colony is to convert nectar and pollen into bees and honey. The main deleterious effect of nosema may not be bee mortality, but rather the fact that infection suppresses efficient food conversion.

Nosema and Energy Metabolism

The point of the above graphs is that we beekeepers are keeping an exceptional animal! In order for a colony to perform to our expectations, it can’t afford to be handicapped by a parasite that messes with its digestion or saps its energy. Yet nosema does exactly that!

Dr. Dhruba Naug and Chris Mayack (2009) have been pioneers in this avenue of research. Allow me to quote some excerpts from their paper:

“Parasites are dependent on their hosts for energy to reproduce and can exert a significant nutritional stress on them. Energetic demand placed on the host is especially high in cases where the parasite-host complex is less co-evolved” [perhaps as in the case of N. ceranae and Apis mellifera?].

“Some pathogens such as microsporidians are particularly severe on their hosts in terms of exerting an energetic stress because they lack mitochondria and therefore have little metabolic ability themselves” [nosema is unable to digest sugar by itself, and steals energy directly from the bees’ metabolic pathway].

“These results demonstrate that energetic stress is the probable cause of the shortened life span observed in infected bees.”

The authors also noted that bees exhibiting an infection of only a quarter of a million spores per bee were hungrier than uninfected bees. They exhibited greater responsiveness to sugar and consumed about half again as much sugar per day.

At this point, I suggest that if you haven’t yet read Bernd Heinrich’s (2004) seminal book “Bumblebee Economics” that you stop right now and order it! Heinrich clearly explains how bee survival is all about energy balance and efficiency. This readable and fascinating book will give you a far greater appreciation and understanding of the economics of the hive, and of ecology in general.

Take home message: As Bernd Heinrich explains, for a colony to be successful, every worker bee must, over the course of its adult life, not only repay the colony’s investment of protein and energy used in rearing that bee to adulthood, but must then additionally forage for enough resources to support itself and to provide for additional broodrearing. Prior to its death, it will ideally produce a surplus of energy stores in the form of honey, which the colony can later use to survive dearth or winter. Any bee that, due to being parasitized by nosema, is unable to fulfill the above responsibilities would then be a net liability, rather than an asset, to the colony as a whole.

Heinrich focused upon bumblebees, but other authors soon followed suit with studies on honey bees. One excellent model of honey bee economics was published by Jon Harrison and Jennifer Fewell (2002). They worked up calculations for net forager caloric gain to the colony after subtracting the costs of colony metabolism and the energy necessary for foraging flight (Table 1).

Table 1. The economy of bee foraging energy gains vs. costs. Table modified after Harrison and Fewell (2002) by permission. By their calculations, in warm weather, the net energetic gain per forager per day is about 2167 Joules, which translates (by my calculations) to 1/50^th of a teaspoon of stored honey per day, or a bit less than 4 lbs of honey for a colony with 10,000 foragers.

Harrison and Fewell’s excellent model was a great starting point for me to try to gauge the effect of nosema infection upon colony weight gain. I know how my readers just love when I take the burden off their TV-addled brains and grind through the math for them, so I entered all of the data from the table above into my own spreadsheet. Luckily, my son volunteered to drive, so I was able to figure out most of the equations while we were hauling a load of hives down to almonds.

When I created a spreadsheet for a colony of 40,000 bees (about 23 frames of bees), assuming that a quarter of them were foragers (Winston 1987; a larger proportion than estimated by Harrison), the resulting daily weight gain or loss figures didn’t necessarily match those that I typically observe in the field (about a pound a day weight loss when confined by rain, and about 5 lbs per day net gain during a decent honey flow). So I adjusted the assumptions using other researchers’ measurements (Southwick 2001; Woods 2005) until the model better reflected field reality.

I got some interesting results. In warm weather, when there is only enough of a nectar flow such that the colony is just holding its own (neither gaining nor losing weight), one forager is essentially gathering enough nectar to feed itself, plus about three house bees, which kinda makes sense if a quarter of the bees are foragers! (A larger proportion may shift to foraging during an intense flow (Oliver 2010)).

However, given the exact same colony, with the same nectar income, but on a cool day, the colony will lose over a pound of weight a day, due mainly to the increased metabolic cost of foraging at lower air temperature.

Pay attention: This is likely a significant point to keep in mind, as nosema infection appears to mainly be a problem in cool weather. The energy economy of a bee colony is much more tenuous when bees must forage in cold air.

OK, now let’s go back to warm weather, again with enough of a light nectar flow that the colony is just able to hold its weight. Then add a nosema infection to the equation, such that half the field force is infected; and guesstimate that the cost of infection results in a 50% increase to the metabolic demand of the infected foragers (Mayack 2009, Martín-Hernández 2011). Without changing anything about the foraging trips or bloom, and without any bee mortality, the cost of the infection would result in about a half pound weight loss for the colony a day!

The infection above would be completely invisible to the beekeeper—the bee and brood population would be exactly the same, the number of foragers and the nectar income would be exactly the same, but the added metabolic cost of the nosema infection to only half the foragers (1/8^th of the colony population) would cause that colony to lose significant weight rather than holding its own.

It gets even worse in cool weather. Everything else remaining the same except for the greater heat loss from the foragers to the cool air (I’m ignoring any additional heat loss by the cluster), the colony would now lose over a pound a day—more than it would if the foragers were simply kept in by poor weather! The model suggests that the impact of nosema infection upon energy dynamics will be most substantial during cool weather or in times of nectar dearth when bees are engaged in fruitless foraging (like sitting in the orchards just prior to almond bloom).

Keep in mind that in recent years, surveyed U.S. beekeepers most often ranked colony starvation as the major cause of winter losses (vanEngelsdorp 2012). I’m thinking, if nosema infection results in less honey being stored over the season, and less efficient metabolism of that honey in cool weather, then perhaps nosema could be an indirect factor in these starvation losses.

You may be wondering what the model predicts for the impact of nosema infection during the main honey flow. Things change quite a bit when colonies are large, the weather is warm, the days are long, and foraging trips are richly rewarded. In a strong nectar flow in warm weather, the model predicts that a 50% infection rate of the foragers would not suppress honey production to any great degree.

But that’s only half the story—because by that time, nosema may have already done its damage during the colony buildup period prior to the main flow.

Nosema and Protein Metabolism

So let’s look at the main limiting factor for colony buildup. Colony buildup, given enough available honey, is limited by the protein income from pollen, and then the ability of young bees to efficiently convert that pollen into jelly.

It may be that the main problem with nosema infection is its impact on the protein dynamics of the hive. Not only do the foragers have a more difficult time energetically in foraging for pollen, and a reduced flight range, but the colony may “starve” for protein despite its being brought in, if infected nurse bees can’t efficiently convert it to jelly. There is a fairly rapid turnover of protein within bee body tissues (Crailsheim 1986), so any hampering of protein processing could really throw a stick into the gears of the hive economy.

Nosema infection of the gut cells has an insidious effect. Not only does it reduce the ability of the gut to digest pollen and then absorb its nutrients, but it diverts protein that would normally go to jelly production into the replacement of damaged gut cells (Fig. 4). As a result, the hypopharyngeal glands tend to “dry up” in infected bees, and they can no longer feed the queen nor the brood.

Figure 4. Cross section of the midgut wall of a bee infected by nosema.   The parasite infects the epithelial cells (ep) which form the intestinal villi (the finger-shaped projections through which nutrients are absorbed).  The epithelial cells naturally break off from the tips of the villi and are replenished by fresh cells regenerated at the basal membrane (bm), which N. ceranae may also infect.  Infected mature epithelial cells fill with nosema spores (dark ovals), which are released when those cells are shed into the gut lumen. There is a greater overturn of the epithelial layer in infected bees, as the bee tries to generate cells faster than nosema can infect them.  This increased replacement rate requires the diversion of protein that would normally go into other tissues or jelly production.  Drawing by G.F. White (1919) Nosema-Disease.  USDA Bulletin No. 780.

So let’s look at the protein cost of nosema to colony buildup. In Figure 2, those pre-varroa colonies built up damn quick! They multiplied their populations fivefold in two brood cycles! That works out to a daily intrinsic rate of increase (r) of 1.04 (1.04% compounded daily for 42 days equals 5x increase).

So let’s factor in the potential drain to colony protein dynamics due to nosema. Unfortunately, I’m going to have to guesstimate here, since I haven’t found any studies in which the jelly production suppression due to nosema infection was clearly quantified. So I’m going to assume for modeling purposes that any badly-infected bee removes one “bee share” of contribution toward brood production.

So, let’s say that a quarter of the bees in the hive were infected; which would then depress the intrinsic rate of increase by a quarter, from 4% to 3% (r of 1.04 to 1.03). At that rate, a 2-lb package, instead of growing into a 24-frame honey-producing monster by the end of 10 weeks, would cover only 17 frames—you’d only get 2/3rds of normal colony growth! And that’s not even taking into effect the increased nosema-induced mortality of the package bees prior to the first brood emerging.

And yet again, the colony would appear to be perfectly healthy, with no brood mortality nor dead bees evident–it would just seem a bit lethargic in buildup. This is why nosema is called the “invisible disease.” And about half of all U.S. colonies now test positive for Nosema ceranae to some degree! It sure makes me wonder if we haven’t been paying enough attention to this new parasite.

Fundamental concept: honey bee colonies are by necessity voracious consumers of high-protein, high-energy food. Anything that affects the digestion and utilization of that food will negatively affect colony buildup and survival. Nosema siphons off a share of that protein and energy.

Practical application: Porrini (2011) and other researchers have found that infected bees can live nearly as long as uninfected workers provided that they receive plenty of protein. But at the same time, nosema spore counts get higher in protein-fed bees. I’d personally worry more about protein deficiency than spore counts! Making sure that your bees get plenty of nutritious pollen or supplement can greatly help to mitigate the deleterious effects of nosema infection.

Nosema and Colony Population Dynamics

You may have noticed that in this article I’m ignoring any increased worker mortality due to nosema. As I explained before, it is not in the interest of the parasite to bring about the death of its host. Rather, the effect of nosema is to turn a colony from a honey-producing factory into a spore-producing factory.

Should there be good weather and plenty of pollen and nectar, and if the colony has a vigorous queen, it can typically purge itself of all but a residual level of nosema infection. However, that colony may not be the sort of robust, productive colony that we are accustomed to. Not only is the colony handicapped by energy and protein competition with the parasite, but infected young bees tend to shift to foraging behavior earlier in life. Since the clock for bee “aging” doesn’t start to tick until a bee begins foraging, such a shift to earlier foraging means that the colony population buildup rate (the slope in the earlier graphs) would be further suppressed due to decreased worker mean lifespan. Again, this would not be due to direct bee mortality due to infection, but from reduced overall lifespan as a result of premature foraging.

“Fragile” Bees

And how about those “fragile” bees that we keep hearing about, that no longer recover from pesticides or viral infections the way that they used to? Could nosema be involved? I’ve seen the spore count reports from a number of commercial operations. In light of what I’m learning about the effects of nosema upon colony buildup, it may not be surprising that their colonies don’t rebound as well as they used to! It may simply no longer be possible to run bees to back to back in pesticide-laden pollination contracts without helping the bees in some way to get ahead of nosema.

Bottom line: These insidious effects of Nosema ceranae may well be related to why today’s successful commercial beekeeper is forced to requeen two or three times annually, to feed more syrup, and to feed much more supplemental protein. Let me state emphatically that I’m not sure about this, but the pieces sure seem to fit together!

We still have much to learn about the effects of Nosema ceranae infection upon colony energy, protein, and immune dynamics. I commend U.S. researchers Chris Mayack, Dhruba Naug, Ann Gibbs, Michael Goblirsch, Zachary Huang, Marla Spivak, and Frank Eischen for their work on this avenue of research (my apologies to those I’ve left out). I especially wish to thank Mariano Higes’ team for putting together an overall picture of the possible impacts of infection, well-reviewed by Raquel Martín-Hernández (2011).

Perspective

I apologize to my readers that this article is lacking in direct practical applications, other than that I suggest that perhaps we should start paying a bit more attention to Nosema ceranae. I realize that the tone of this article may lead some to freak out about this parasite, but I wish to emphatically state that that is not what I had in mind!

Lest I overplay the consequences of the presence of N. ceranae, remember that I’ve successfully run my California operation for many years without using any medications against nosema, so I’m certainly not recommending that you blindly start dumping medications into your hives. This winter is the first time that I’ve used any treatments—and I only treated colonies that clearly had problems.

Not all scientific studies have found benefit to treatment. Traver (2011) reports that in Virginia “we observed very little impact of Nosema infections on either colony growth or productivity, suggesting that even though we found higher levels of infection, treatment is not necessary.”

I’ve personally watched colonies with mean forager spore counts in the 5M range build up explosively and put on good honey crops, provided that forage conditions were good. But keep in mind that when I measured those counts, I wasn’t yet determining nosema prevalence (the proportion of foragers infected), so I really don’t know just how badly those colonies were actually infected.

I know of large commercial operators whose colonies had sky-high spore counts in spring, yet went on to be extremely productive without treatment.

On the other hand, in the majority my strongest colonies this December, zero out of 10 sampled bees were infected by nosema, and in no case were more than 1 out of 10 infected. But nosema prevalence was typically higher in my weakest colonies.

Somehow my strongest colonies appear to be holding their own against nosema just fine without treatment. I plan to test again at the end of almond pollination to see how they are faring at that time, as last year spore counts were quite high in the bee net samples from my returning truckloads.

Please be clear that I don’t want to sound alarmist about N. ceranae, yet I feel a responsibility to my readers to keep them abreast with recent research. In this article I’ve been thinking aloud, and have yet to reach firm conclusions. However, the evidence continues to mount that N. ceranae may be more of a problem than it originally appeared. I will go into more detail in subsequent articles.

References

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