Reduced toxin binding associated with resistance to Vip3Aa in the corn earworm ( Helicoverpa zea )

is a major crop pest in the United States that is managed with transgenic corn and cotton that produce insecticidal proteins from the bacterium, (Bt). However, has evolved widespread resistance to the Cry proteins produced in Bt corn and cotton, leaving Vip3Aa as the only plant-incorporated protectant in Bt crops that consistently provides excellent control of . The benefits provided by Bt crops will be substantially reduced if widespread Vip3Aa resistance develops in field populations. Therefore, it is important to identify resistance alleles and mechanisms that contribute to Vip3Aa resistance to ensure that informed resistance management strategies are implemented. This study is the first report of reduced binding of Vip3Aa to midgut receptors associated with resistance.