This past growing season was good for evaluating the impact of a variety of environmental factors on corn yield, such as nitrogen losses, hail damage, green snap, etc. It was not, however, a particularly good growing season for evaluating the damaging effects of European corn borer. Insect pressures were fairly light across the state. The light insect pressures coupled with the effects of one or more environmental factors made Bt hybrid evaluations challenging in 1998 (i.e., it was difficult to identify exactly what caused yield variability). Presented herein are the results from replicated field trials conducted by Iowa State University in 16 Iowa counties
