In the second study discussed in the article, researchers at Kansas State University reported in Science that they had discovered corn borer resistance to Bt toxins. Shelton and Roush question the methodology used in the study, "including that the authors did not demonstrate that resistance was actually to the same Bt toxin as in the plant or that the insects could survive on the Bt plant." Even so, they write, "this questionable laboratory study has generated considerable debate over whether the present resistance management policy should be overturned."
In another recent issue of Nature, a University of Arizona study showed that the pink bollworm's resistance to Bt-cotton was recessive in inheritance, but the paper questioned whether resistant bollworms developed more slowly than susceptible bollworms. This could possibly knock out random mating and dilute the insect's resistance in the field. "We hope that the take-home message won't be converted to another premature claim that Bt crops are doomed," Shelton and Roush say in their commentary.
Since the release of the monarch butterfly study, write Shelton and Roush, companies that make the genetically engineered agricultural seed have been confronted by freezes on the approval process for Bt transgenic corn by the European Commission and by "possible trade restrictions by Japan." In the United States, there have been calls for a moratorium on the further planting of Bt-corn.
In discussing the Cornell monarch butterfly report, Shelton and Roush voice
their surprise that a "previous and more relevant and realistic study has been
largely overlooked." While the Cornell laboratory study showed high mortality
among monarch larvae that ingested genetically engineered pollen, an Iowa State
University study by Laura Hansen and John Obrycki showed low mortality even when
Monarch larvae were fed milkweed that had the highest levels of Bt pollen that
would be encountered in
Contact: Blaine P. Friedlander Jr.
Cornell University News Service