Performance of Field Populations of Helicoverpa Zea Against Pyramided Bt Corn and Purified Vip3Aa1 Protein

In this study, occurrence and ear damage of the corn earworm, Helicoverpa zea (Boddie), were first evaluated against different non-Bt and pyramided Bt corn varieties in the field. The results showed that Bt corn containing Cry1Ab+Cry1F and Cry1A.105+Cry2Ab2 technologies are not effective against H. zea, with no differences on larval occurrence and ear damage relative to that on the non-Bt corn. However, unexpected number of larvae and ear damage were detected on the Cry1Ab+Cry1F+Vip3A corn, with 0.79 larvae per ear and 67.5% damaged ears. Diet-overlay bioassays showed that the resistance ratio of the H. zea population collected from Cry1Ab+Cry1F+Vip3A corn was 20.4-fold compared with the population collected from Cry1A.105+Cry2Ab2 corn.