Pollen contamination, occurrence and ear damage of corn earworm in mixed plantings of non-Bt and pyramided Bt corn

Pollen contamination, occurrence and ear damage of corn earworm (CEW) were evaluated in three different planting patterns of seed mixtures of non-Bt and Bt corn containing Genuity^® SmartStax^TM and Agrisure^®Viptera^TM 3111 traits. The three planting patterns were 1) pure stand of 27 Bt plants; 2) pure stand of 27 non-Bt plants; and 3) one non-Bt plant in the center surrounded by 26 Bt corn plants (RIB). The number of eggs laid by CEW was similar between Bt and non-Bt corn ears regardless of the planting patterns and corn products. Pyramided Bt corn hybrids were highly effective for CEW control with virtually no larvae or ear damage on the ears. Due to cross-pollination, a high proportion of kernels of refuge plants in RIB planting were contaminated to express Bt proteins. The intensive contamination of Bt proteins in refuge ears didn’t reduce the larval survival at early stages (e.g. 3-4 instars), but development of the larvae was significantly delayed compared to that on pure non-Bt corn ears. Information generated from this study should provide useful information to improve resistance management modeling for Bt corn. Further study should focus on the effect of Bt protein contamination on the full life cycle of CEW.