Evaluating the flight performance of Helicoverpa zea populations carrying different Cry and Vip3A resistance alleles

The corn earworm (CEW), Helicoverpa zea, is a highly mobile and economically damaging pest of corn and cotton in the U.S. It annually migrates northward from overwintering regions in the southern U.S. to the Corn Belt. This long-distance seasonal movement facilitates rapid gene flow and the widespread dissemination of adaptive traits, such as Bacillus thuringiensis (Bt) resistance alleles. In recent years, CEW has evolved widespread practical resistance to Cry1Ac and Cry2Ab2 across the U.S., and early-warning resistance to Vip3Aa in the Mid-South and Texas, raising serious concerns about the landscape-level spread of Vip3Aa resistance alleles and the durability of Vip3Aa for CEW control. Previous studies suggest that insect resistance to Bt proteins is sometimes associated with fitness costs, such as reduced pupal size, decreased survival, and slowed growth rate. Such fitness costs may impact dispersal potential and the spatial dynamics of resistance allele spread. However, the effects of Bt resistance associated fitness costs on CEW flight performance and dispersal capacity remain poorly understood. In this study, we used a flight mill system to compare the flight performance of CEW individuals carrying different combinations of resistance alleles to Cry1/Cry2, and/or Vip3Aa proteins. A total of thirteen different insect genotypes of CEW were tested for flight propensity, distance, duration, and speed over a 24-hour period under controlled conditions. These findings provide insights into how Bt resistance may impact CEW dispersal and the spread of resistance alleles, with important implications for resistance management and the preservation of Bt crop efficacy.