Complexities in a cornfield--nontarget impacts of Bt corn

May Berenbaum, Head of Entomology, UIUC

Although agroecosystems are greatly simplifield in comparison with natural systems, they still present tremendous complexities that challenge efforts to protect crop plants from insect damage. The widespread adoption of transgenic corn expressing Bacillus thuringiensis endotoxin (Bt corn) for management of European corn borer (Ostrinia nubilalis) raised concern over the possibility of adverse impacts on nontarget lepidopterans (including Danaus plexippus, the monarch caterpillar) through movement of the Bt endotoxin protein in corn pollen. Laboratory and field studies demonstrated that the potential for adverse impacts on nontarget lepidopterans varies with the specific Bt corn event and with environmental conditions. Moreover, environmental impacts of Bt corn must be evaluated in the context of other mortality factors in effect in cornfields, including nontarget impacts of biological control programs in other agricultural systems. These studies demonstrate dramatically the impossibility of creating agroecosystems that have no adverse impacts on the natural landscape in which they are embedded.

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