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Date: | Sun, 25 Nov 2007 18:42:56 -0800 |
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Bob Harrison wrote:
> I am not saying BT corn pollen is the cause of CCD but do
> believe that the BT pollen does raise health concerns for
> honeybees.
Bob, what specific bee health concerns do you have
about BT corn pollen?
Earlier this year Galen P. Diveley at the University of Maryland
(a researcher who also had previous experience
evaluating the effects of BT corn on the monarch butterfly)
published an article: "Bt corn cleared in Colony Collapse Disorder"
http://www.americanfarm.com/TopStory5.01.07f.html
Excerpts: "The endotoxins currently expressed in Bt corn (Cry1
types against caterpillars; Cry3 types against beetles) are not
biologically active against hymenopteran insects such as the
honey bee, nor do the CCD symptoms resemble those expected
in Bt intoxicated organisms. Exposure is also very low because
the expression of endotoxins in pollen is barely detectable in
most Bt corn hybrids and corn does not produce nectar. For
these reasons, bees are not commonly found foraging in corn
fields."
Numerous laboratory studies have examined the potential
non-target effects of Bt corn on honey bees by feeding high
doses of the pollen or purified endotoxin mixed with honey
or sugar syrup directly to larvae in brood cells. Published studies
and other technical reports submitted to EPA have all shown
no adverse acute effects. In particular, recent laboratory
studies in New Zealand and Switzerland exposed bees by
feeding on pollen treated with purified Cry1 endotoxins at
doses considered well above the maximum environmental
exposure levels encountered in the field. Results showed
no negative effects on bee survival.
Laboratory feeding studies at the University of Maryland also
showed no effects on the weight and survival of honey bees
feeding on Cry1Ab-expressing sweet corn pollen for 35 days.
A two-year field study (soon to be published in the
European bee journal Apidologie) conducted by this author
and his graduate student represents the first attempt to
expose functional colonies of honey bees to Bt corn pollen
under open field conditions. In this Maryland study,
colonies placed in Bt sweet corn plots were allowed to
forage on corn pollen and also fed Bt pollen cakes for 28 days.
The pollen cake consumption alone represented approximately
44 percent of the expected daily pollen requirements of each
exposed hive. Results showed no adverse effects on bee
weight, foraging activity, colony bee strength and brood
development.
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