Study: Biotech Corn Kills Monarch

Paul Cherubini cherubini at
Tue Aug 22 05:27:11 EDT 2000

The article posted by Jeffrey Caldwell stated:

> The Iowa State researchers planted breeds of biotech corn that
> produced different levels of the insecticide pollen along with some
> corn that hadn't been engineered. They then placed potted milkweed
> plants at varying distances from the fields. After two or three
> days they took the milkweed plants into the lab and exposed the
> caterpillars to the plant leaves.

My understanding is that in the original Cornell study, Dr. Losey 
found some monarch caterpillars died when FORCED to eat
milkweed artifically dusted with Bt corn pollen in the LABORATORY. 

The Iowa State Researchers appear to have repeated Losey's 
LABORATORY FORCE FEEDING experiment using naturally
dusted milkweed. Forced feeding = forced exposure.

IMHO, the severe limitation of this new Iowa State study, just like the
original Cornell study is that it fails to address the crucial question
of real world larval exposure to toxic levels of Bt corn pollen.

We know some monarchs lay eggs on milkweeds
growing on the edges of both Bt corn fields and conventional corn
fields. We know pollen accumulates on the leaves of these milkweed
plants for a brief period in late July.  But how does the survivability of 
UNMANIPULATED caterpillars developing on those plants 
(NOT FORCED TO FEED ON THE POLLEN) differ (if at all)
between a Bt corn field vs. a conventional corn field?  The Iowa 
State Study does not answer this question. 

Unmanipulated caterpillars in the field may exhibit a variety of
behaviors that inadvertently help prevent the ingestion
of toxic amounts of foreign matter like road dust or pollen.  This is the
reason why insecticide manufacturers never rely on lab studies
of efficacy in deciding whether or not to bring a new insecticide
to the market. They know that what happens in the lab cannot be
extrapolated to the field, hence they conduct years of real world field
trials before deciding whether or not a new candidate insecticide 
is as good or better than other products on the market.

Paul Cherubini

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