Because rainfall repeatedly reduced pollen concentrations during the summer 2000 test period, the results must be considered conservative, the scientists said.
The findings and those of five other related projects done elsewhere, and which also targeted Bt corn, appear online this week in the Proceedings of the National Academy of Sciences. The papers are being released ahead of publication at the request of the U.S. Environmental Protection Agency.
The results of this study suggest that pollen from Bt corn varieties engineered with the 176 event may have sublethal effects on black swallowtails (Papilio polyxenes) feeding on host plants situated outside of cornfields, the authors wrote. Researchers also attempted to study the effects on monarch butterflies (Danaus plexippus), but a high death rate was believed to be more likely the result of predation than proximity to pollen.
Bt corn refers to genetically modified varieties that resist the European corn borer (Ostrinia nubilalis). Bt is short for Bacillus thuringiensis, a soil organism that produces toxic proteins that kills the borers, which cause $1 billion in crop damage annually in the United States. Scientists can control when and in what part of the plant the toxin is produced by combining gene sequences with specific promoters. Successful transformations of corn with the genetically engineered sequences are called events.
The UI team, led by entomologists May R. Berenbaum and Arthur R. Zangerl, planted Novartis Max 454 Bt corn, which contains Novartis event 176, in a 30-by-30 meter tract northeast of the UI campus in late May 2000.
This variety of Bt corn is known to produce pollen with higher concentrations of the pesticide
Contact: Jim Barlow
University of Illinois at Urbana-Champaign