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John McDonald, Special to The Chronicle
San Francisco Chronicle, March 10 2007
original article
With reports coming in about a scourge affecting honeybees,
researchers are launching a drive to find the cause of the
destruction. The reasons for rapid colony collapse are not clear. Old
diseases, parasites and new diseases are being looked at.
Over the past 100 or so years, beekeepers have experienced colony
losses from bacterial agents (foulbrood), mites (varroa and tracheal)
and other parasites and pathogens. Beekeepers have dealt with these
problems by using antibiotics, miticides or integrated pest management.
While losses, particularly in overwintering, are a chronic condition,
most beekeepers have learned to limit their losses by staying on top
of new advice from entomologists. Unlike the more common problems,
this new die-off has been virtually instantaneous throughout the
country, not spreading at the slower pace of conventional classical
disease.
As an interested beekeeper with some background in biology, I think
it might be fruitful to investigate the role of genetically modified
or transgenic farm crops. Although we are assured by nearly every bit
of research that these manipulations of the crop genome are safe for
both human consumption and the environment, looking more closely at
what is involved here might raise questions about those assumptions.
The most commonly transplanted segment of transgenic DNA involves
genes from a well-known bacterium, bacillus thuringiensis (Bt), which
has been used for decades by farmers and gardeners to control
butterflies that damage cole crops such as cabbage and broccoli.
Instead of the bacterial solution being sprayed on the plant, where
it is eaten by the target insect, the genes that contain the
insecticidal traits are incorporated into the genome of the farm
crop. As the transformed plant grows, these Bt genes are replicated
along with the plant genes so that each cell contains its own poison
pill that kills the target insect.
In the case of field corn, these insects are stem- and root-borers,
lepidopterans (butterflies) that, in their larval stage, dine on some
region of the corn plant, ingesting the bacterial gene, which
eventually causes a crystallization effect in the guts of the borer
larvae, thus killing them.
What is not generally known to the public is that Bt variants are
available that also target coleopterans (beetles) and dipterids
(flies and mosquitoes). We are assured that the bee family,
hymenopterans, is not affected.
That there is Bt in beehives is not a question. Beekeepers spray Bt
under hive lids sometimes to control the wax moth, an insect whose
larval forms produce messy webs on honey. Canadian beekeepers have
detected the disappearance of the wax moth in untreated hives,
apparently a result of worker bees foraging in fields of transgenic
canola plants.
Bees forage heavily on corn flowers to obtain pollen for the rearing
of young broods, and these pollen grains also contain the Bt gene of
the parent plant, because they are present in the cells from which
pollen forms.
Is it not possible that while there is no lethal effect directly to
the new bees, there might be some sublethal effect, such as immune
suppression, acting as a slow killer?
The planting of transgenic corn and soybean has increased
exponentially, according to statistics from farm states. Tens of
millions of acres of transgenic crops are allowing Bt genes to move
off crop fields.
A quick and easy way to get an approximate answer would be to make a
comparison of colony losses of bees from regions where no genetically
modified crops are grown, and to put test hives in areas where modern
farming practices are so distant from the hives that the foraging
worker bees would have no exposure to them.
Given that nearly every bite of food that we eat has a pollinator,
the seriousness of this emerging problem could dwarf all previous
food disruptions.
John McDonald is a beekeeper in Pennsylvania. He welcomes comments or
questions about the bee problem at mcbee_77@yahoo.com. General
comments to home@sfchronicle.com.
This article appeared on page F – 4 of the San Francisco Chronicle
