Monday, May 24, 1999
Anyone who picked up a newspaper last week saw agbio's worst
nightmare to date: Headlines and color photos of a genetically modified plant
that kills butterflies.
As a result, the public now may be convinced that Bt corn poses
a grave environmental risk. Thus while it may be relatively easy to question
the quality of the laboratory finding at Cornell University, agbio advocates
will be challenged to raise a scientifically compelling case refuting the implications
of the study, focusing on real world conditions, and showing what happens in
actual practice through rigorous field tests.
The controversy was spurred by a letter to Nature from
Cornell researchers, who reported that monarch butterfly larvae were killed
by pollen from corn genetically modified to express Bacillus thuringiensis,
a natural toxin.
From a scientific point of view, the outcome was not surprising.
Leptidoptera are related to European corn borers, the target of Bt pesticides.
The toxic effects of Bt on monarchs and other lepidoptera "have been reported
in the scientific literature and/or regulatory review documents since at least
1986," according to Val Giddings, vice president for food and agriculture at
the Biotechnology Industry Organization.
Richard Lottstein, director of regulatory and government affairs
at Novartis Seeds, whose Bt corn was used in the study, said "it is well known
and in the scientific literature that Bts such as the Bt in our corn are specific
for lepidoptera and larvae. That a lab test showed that you could force an effect
on another lepidoptera using a Bt is not a surprise. The real question is does
it have any relevance to real life in the field. We don't think this study shows
there would be relevance."
In the Cornell laboratory, 56 percent of larvae survived after four days of feeding on milkweed leaves dusted with pollen from Bt corn, compared to 100 percent survival for larvae feeding on leaves dusted with untransformed pollen or leaves with no pollen (see B18). Larvae feeding on leaves with Bt corn pollen also grew more slowly.