Recent advance in Vip3Aa resistance of Helicoverpa zea in the United States

Helicoverpa zea, commonly known as the corn earworm, is a major pest targeted by Bt cotton and pyramided Bt corn in the United States. However, resistance poses a significant threat to the long-term effectiveness of Bt crops as a pest management tool. The efficacy of Bt Cry proteins against H. zea has been greatly diminished by resistance in the southern U.S., leading to a rapid adoption of Bt cotton and corn expressing the Vip3Aa protein. The evolution of Vip3Aa resistance has been accelerated by increased use of Vip3Aa technology, poor compliance with corn refuge requirements, and resistance to Cry proteins. In this study, we report the results of our recent monitoring efforts on Vip3Aa resistance in H. zea, including the susceptibility and resistance allele frequency of field populations to Vip3Aa, the inheritance of resistance, cross-resistance, and fitness costs in different resistant populations of H. zea.