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."

The study

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.