Lepidopteran control in field corn using new Bt trait combinations

Corn earworm, Helicoverpa zea (Bobbie), and fall armyworm, Spodoptera frugiperda (J.E. Smith), are key lepidopteran pests of corn in the southeastern United States. Single gene Bt traits (Cry1Ab and Cry 1F) were variable in efficacy against corn earworm in the ear. Serious defoliation by large infestations of fall armyworm also can occur in hybrids with the Cry1Ab gene. Efficacy of the Mon 89034 event with Cry2Ab2 gene in combination with a modified Bt gene (Cry1A.105) for corn borer control in several combinations is presented. These pyramided Bt lines provide improved control of corn earworm and prevent most kernel damage. Ear infestations were reduced on average by about 70% and kernel damage was reduced by an average of 90%. Grain yield responses were variable but improved grain quality was observed when earworm infestations were large. No consistent effect on grain aflatoxin contamination was found in this limited number of trials. The most consistent benefit from the new Bt traits was found in later corn planted after the recommend planting time.