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Wednesday, April 4, 2007

On Bees, Or, An Apple A Day May Be A Thing Of The Past

America employs a massive army of migrant farm workers, who rise from their winter slumber every year and travel from farm to farm, helping to prepare the crops.

From October to December of 2006 they started vanishing in unprecedented numbers. Many of the ones who survive have suffered massive injuries from an unknown agent; and it is possible that crops from apples to pears to avocado will no longer be produced in the US as a result.

Who are these workers? Honeybees.

Why does this matter? Bees pollinate crops, you may recall, and without the efforts of bees it would be impossible to produce many of the things you expect to find at the grocery store. Almonds, apples, avocados, and sugarbeets (think crop based fuels here) are all 90% or more dependent on bee pollination. Not to mention honey. (Corn, rice, and wheat are pollinated by the action of the wind, and are not pollinated by insects.)

Honeybees are not the only pollinating animals. Wasps and other “bee types”, ants and beetles, butterflies, hummingbirds, and even bats also pollinate. Each, however, presents unique management issues that have prevented their widespread adoption as tools of the farming trade.

The dollar value of all these potentially lost crops may exceed $15 billion.

How bad is the problem? A beekeeper in Georgia reports that he only expects 9 of his 1200 beehives to survive. There are concerns that the beekeeping (apiary) industry may not recover. Other apiasts report losses of 30-90% of their bees.

The spread of Colony Collapse Disorder can be seen on this map.

The cause of Colony Collapse Disorder is currently unknown.
It is known that this Disorder is highly unusual for several reasons:

--the collapse of colonies is massive and sudden, which is unprecedented.

--unlike bee disease outbreaks in the past, it is almost impossible to locate dead bees in or near the hives.

--in affected colonies, virtually all older worker bees are absent, with a queen, larvae, and young adult bees being the only remaining hive residents.

--in an extremely disturbing development, empty colonies, which are full of highly desirable nectar, honey, and royal jelly (more on this later) are not immediately “poached” for their food by other normally opportunistic insects, such as the wax moth. Insects appear to be unwilling to access these free food supplies for at least two weeks following a hive collapse.

--there are extensive anatomical abnormalities, from the thorax to the sting gland, which seem to be associated with the presence of one or more pathogenic agents not currently identified.

--the affected bees are both unwilling to feed (yes, beekeepers feed their charges) and apparently unable to digest pollen, as undigested pollen grains have been found in the digestive tracts of live bees.

At this point in the discussion, some background is in order.

Most beekeepers, as discussed above, travel from place to place renting their bees to farmers.

There were about 2.4 million hives in production at the end of summer 2006, with 1/3 of those in California. There will not be that many in the summer of 2007.

Despite that number, apiasts must come to California to supplement the State’s bee supply by an additional 600,000 colonies every year just to pollinate the almond crop. (It can cost up to $150 per day per colony for this service.)

A bacillus was associated with the American Foulbrood disease. It is considered the most serious of bee pathogens, and outbreaks resulting in extensive die-offs of bee colonies occurred in the 1940’s. Antibiotics have controlled this pathogen since then.

The Varroa mite was implicated in the near complete elimination of bee colonies in the wild during the 1990’s; a second mite (the tracheal mite) is not well understood. Neither mite was discovered until the 1980’s.

Here is a great page taking you through the biology of a bee. I’ll quickly tell the story below.

There are three kinds (“castes”) of bees. Queens live one to a hive, and basically do nothing but eat, lay eggs and generate a pheromone that prevents the other females in the colony from wanting to reproduce. A newly hatched queen will kill all other queens present, including her mother and sisters.

Mating occurs when a “virgin” queen, having just killed any other potential queens, takes her “mating flight”. In this flight she interacts with drone (male) bees who deposit, literally, a lifetime of sperm which she will store in a specialized gland. Sadly (or not, depending on your perspective), the event is fatal for the drones. The interaction with multiple drones appears to be an effort to create genetic diversity.

Queens have the option of fertilizing an egg with her stored sperm. If this occurs, a drone will hatch. Drones have no purpose other than mating, and over the winter no males will be present in the hive.

Non-breeding female (worker) bees are the result of unfertilized eggs, and vastly outnumber the other two types of bees.

Eggs are deposited in the familiar hexagonal cells of the honeycomb. (Brood comb is the term for the portion of the comb that actually contains eggs, as opposed to the food storage portion of the comb.) It surprised me to learn that workers prepare a unique peanut shaped cell which is kept in reserve in the event the current queen stops producing eggs or pheromone. If this should occur, workers will install a female egg in the cell. About 3 days later the egg will enter its larval stage, and with proper feeding, a queen will develop who will emerge and kill her predecessor.

“It’s good to be the King” Mel Brooks’ Louis XVI character tells us, and, not unlike France, maybe not so good to be the Queen.

The total time from egg laying to emerging from the larval stage as a young adult is 20 days for all three “castes” (Queen, worker, and drone). All larvae will be excessively fed for the beginning of that stage, and then worker and drone larvae will be fed much less often as the larval stage progresses.

It is estimated that worker bees will visit each larval bee 110,000 times during the 16-24 days of the egg and larval stages.

Pollen is the protein source for the colony, and nectar is the carbohydrate source.

Nectar (which is stored in the hive) with moisture content that has evaporated below 18% becomes honey.

Remember Royal Jelly? This most precious of bee foods is a mixture of digested pollen, honey, and bee saliva. In a process reminiscent of the production of fois gras, a female larva is “lavishly” fed this food by older nurse bees to become a Queen.

A lesser food, “bee bread”, consisting of digested pollen and honey, is provided to future worker bees after the first 24 hour feeding of Royal Jelly. They are not fed nearly as often as Queens, and are cared for by older and younger adult worker bees.

The food provided to drones changes from a low-pollen mixture to a high-pollen mixture as the larvae develop. Because drones grow to the largest size of all three castes, they also require the largest quantity of food.

Lifespan? Drones live more or less two months, workers typically live one to four months (shorter in the summer), and Queens can live from two to five tears.

It is possible to “split” a colony to create two colonies, if a new Queen can be provided, and of course, the market has filled this need.

With that out of the way, let’s move on.
Unless linked otherwise, all of the following information is referenced here.

There are commonalities among the affected beekeepers:

--they are all migratory beekeepers. All of the impacted colonies had been moved at least twice; and possibly as many as five times in ’06. (However, reports of major losses to non-migratory keepers can be found here.)

--each experienced at least a 30% mortality rate (a 10% mortality rate is considered normal for “migrant” colonies).

--each has “restarted” a dead colony by using resources from another living colony. The way this works is “dead-out” brood combs (which may or may not contain living larval bees) are placed in physical proximity to a living colony. The workers will then maintenance all the combs. When the Queen lays eggs in the new brood comb it is removed and placed in a new box, creating a new colony. You can see pictures of this process here.

--they all “stressed” the affected colonies in some way. These stresses included overcrowding, pollinating crops with low nutritional value, and drought. (This is not a complete list.)

--none of the keepers used Fumigillin to control nosema disease.

These practices raise the following concerns:

--placing “dead-out” colonies in proximity to apparently healthy colonies may transmit the pathogenic agent to the healthy colony.

--moving colonies, for a variety of reasons, may be stressing the bees, and increasing the possibility of disease.

--moving colonies around the country may be exposing bees to new pathogens.

--splitting out colonies creates stress. This includes the stress of forcing older bees to serve as nurse bees, rather than pollen gathering bees. Because older bees are more likely to have diseases, this increases the possibility that larval bees will be infected at emergence.

Performing examinations of dead bees, normal for this type of investigation, has proved extraordinarily difficult because there aren’t any dead bees to examine. As was mentioned at the top of the diary, this is an unprecedented occurrence.

As a result, scientists are forced to examine living bees, bee bread, and honey. 24 colonies (19 from Pennsylvania, and five from Georgia) were examined.

Examining the dead-out combs does not reveal significant levels of pathogens.

However, examination of the living bees does reveal extensive pathogenic loading (including both viruses and fungi). In fact the samples contained virtually every known bee disorder, and the levels of infection are far more extensive than any previously reported in the scientific literature.

A photograph of the dissected thorax of a bee collected while still alive exhibits discoloration normally associated with dead bees.

Photographs of the normally white “kidneys” (Malpighian Tubules) reveal brownish discolorations. The structures have even disappeared in some samples. Unusual levels of debris are noted in the tubules.

Evidence of fungal infections can be seen in the pyloric scarring evident, the accumulation of immune defense cells near the sting gland, and the visible presence of mycelium, in some cases.

Strange stonelike objects are present in the abnormally transparent rectums of samples from the Georgia colonies that cannot be explained.

One slide revealed a square structure that resembles a known virus, but the structure is ten times the size of that virus. This also cannot be explained.

It has been suggested that symbiotic combinations of crop treatment chemicals may be stressing the bees, allowing these other opportunistic pathogenic agents to take hold in the colonies. A new class of insecticides, the neonicotinoids, has especially attracted the attention of investigators.

There is a research project under way, using the samples, to determine if a currently unknown pathogen exists.

So now what?

The most recent recommendations I’ve seen (dated March 7th) suggest not merging colonies together, isolating affected colonies while research on a “sterilization” process continues, and following specific chemical treatment and feeding processes, with the goal of reducing potential “kidney” damage and other bee stressors.

There was no suggestion that migration from farm to farm be discontinued as a beekeeping practice.

There was no suggestion to the general farming community that changes in the chemicals applied to crops might be in order.

So let’s sum up:

A currently unknown event is causing the disappearance of worker bees from managed bee colonies.

The event has occurred with previously unheard of speed.

This event is unprecedented in its scope, and has the potential to completely alter American agriculture in a manner not yet fully appreciated.

Crops as diverse as grapes, strawberries, ornamental flowers, and all citrus fruit could become nearly impossible to grow commercially as a result of the event.

The living bees examined have pathogen loads never before seen by science.

Beekeepers express doubt that the industry will continue to exist if a solution cannot be found quickly.

There are virtually no feral bees to replace or assist in the rejuvenation of the bee population.

Normally I try to offer a snappy observation to end these discussions, but today I don’t have one.

Let’s hope the bees don’t provide it for us.

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