Study: Biotech Corn Kills Monarch

Cris Guppy & Aud Fischer cguppy at
Tue Aug 22 11:45:16 EDT 2000

Paul seems to be creating an concern with experimental design where none
really exists. In the wild "natural" caterpillars have no more choice in
what they will eat than do caterpillars placed by humans on a plant. The
caterpillar's mother places the caterpillar, in the form of an egg, on a
plant and the caterpillar is then forced to eat that plant (and the pollen
on it) or starve. What difference is there between that and a human placing
the caterpillar on a plant?

Sure, the caterpillars were placed on potted plants that taken into the
laboratory after natural dusting with pollen. But what difference does that
make to thecaterpillars? Whether they are in the wild or in the lab they
have to eat the plant they find themselves on or starve.

As it happens I do not think that Bt pollen from corn will have a very large
effect on the total Monarch population. However it is an indication of the
potential effects on non-target organisms of incorporating Bt genes into
plants. There is extensive research around the world into incorporating Bt
genes into forest trees, to reduce forest pest problems (as documented by a
World Widllife Fund study). Wherever such trees are planted, large numbers
of non-pest Lepidoptera that feed on the alterred trees would have their
populations eliminated or reduced, and IF the gene is incorporated into the
tree pollen as in corn the entire forest ecosystem will be sterilized of
non-target Lepidoptera. Speculation? Yes, but if we do not consider
potential adverse effects before these trees are released into the wild,
then it may be too late at that point.


----- Original Message -----
From: "Paul Cherubini" <cherubini at>
To: <leps-l at>
Sent: August 22, 2000 2:27 AM
Subject: Re: Study: Biotech Corn Kills Monarch

> 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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