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Informed Discussion of Beekeeping Issues and Bee Biology

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Subject:
From:
Paul Cherubini <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
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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