Field Effects of Bt Corn on the Impact of Parasitoids and Pathogens on European Corn Borer in Illinois

The European corn borer completes two to three generations per year in Illinois. Fourth and fifth instars tunnel in stalks, causing disruption in the flow of water and nutrients in the plants. The cavities created by the borers may weaken stalks and ear shanks, resulting in lodging or dropped ears. Before the advent of Bt corn, producers attempted to control European corn borers, if the need arose, by applying insecticides before the larvae tunneled into the corn stalks. However, scouting for European corn borers, especially second generation borers, is arduous, and timing an insecticide application for maximum efficacy is difficult. Consequently, the acreage of corn in Illinois treated with insecticides for control of European corn borers has often been significantly lower than the acreage with economic infestations. In other words, many producers did nothing to manage European corn borers, similar to what has been reported throughout much of the Midwest (Rice and Ostlie, 1997). However, the promise of season-long control of European corn borers with transgenic corn expressing ́-endotoxin proteins from Bacillus thuringiensis Berliner genes (Bt corn) (e.g., Koziel et al., 1993) has encouraged many producers to manage this perennial pest with transgenic Bt hybrids.