CORN EXPRESSING CRY1AB OR CRY1F ENDOTOXIN FOR FALL ARMYWORM AND CORN EARWORM (LEPIDOPTERA: NOCTUIDAE) MANAGEMENT IN FIELD CORN FOR GRAIN PRODUCTION

Fall armyworm, Spodoptera frugiperda (J. E. Smith), and corn ear-worm, Helicoverpa zea (Boddie), perennially cause leaf and ear damage to corn in the southeastern United States. Transgenic hybrids expressing the Cry1Ab (MON810 event) or Cry 1F (TC1507 event) insecticidal endotoxin from Bacillus thuringiensis (Bt) were evaluated for management of fall armyworm and corn earworm in central Georgia during 2006 and 2007. Corn was planted at the recommended time in mid-Apr and in late Jun to simulate a double-crop corn planting. Both Bt events reduced whorl infestation and damage by fall armyworm, but TC1507 provided greater protection from whorl injury than MON 810 under severe fall armyworm infestations. Hybrids with the MON810 event usually had less ear infestation by corn earworm than susceptible hybrids, whereas the TC1507 event usually did not reduce ear infestations. Nevertheless, both events prevented ear damage, but there was no consistent difference between the two Bt traits in preventing ear damage. Bt traits did not affect grain yield in either year during the first planting when fall armyworm infestations were low. Both events prevented significant yield loss during the second planting in 2006 when whorl infestation levels exceeded 50% in susceptible hybrids. Because of the greater activity in preventing whorl damage by fall armyworm, the TC1507 event would be useful in mitigating the risk of severe lepidopteran damage to later plantings of field corn for grain production in the southeastern U.S.