Effect of Bt Expressing Transgenic Corn on Corn Earworm in Soybean.

Corn earworm (Helicoverpa zea Boddie) is an important pest of corn and soybean in the Delaware, Maryland and Virginia (Delmarva) region. Corn serves as a primary nursery for generation turnover of corn earworm populations which eventually shift to soybean later in the growing season. Most of the farmers in the region grow Bt corn. We studied the impact of Bt corn on corn earworm in soybean. Three Bt expressing corn hybrids and non-expressing isolines were planted in the field in replicated field trials. Full grown larvae (prepupae) were collected from Bt expressing corn and non Bt isolines and were placed in emergence cages consisting of inverted, plastic buckets with ventilation holes on the sides. Results showed   that the number of corn earworm moths that emerged from Bt expressing corn hybrids was lower than the moths that emerged from non-Bt expressing isoclines suggesting that the population of corn earworm moths that affect soybean crop later in the season is reduced.