Opportunities & challenges for HearNPV integration of sweet corn pest management programs

Corn earworm, Helicoverpa zea (CEW), is the primary pest of sweet corn in the U.S., often requiring multiple insecticide applications and/or the use of Bt varieties. Resistance to pyrethroids and Bt proteins in CEW populations has created serious challenges for managing this pest. Organic growers, especially, have very few viable options to control CEW. Helicoverpa armigera nucleopolyhedrovirus (HearNPV) offers an intriguing IPM tool to utilize in CEW management programs. However, because HearNPV virions must be ingested, take a few days to kill small larvae, and are not as efficacious on larger instars, the performance of HearNPV in small plot sweet corn insecticide efficacy trials has not been on par with other insecticides. Late timing of application and poor coverage may have contributed to the previous unfavorable results with HearNPV in sweet corn. Recent larger scale trials with air blast spray applications showed that HearNPV significantly increased the number of marketable (undamaged) ears on a commercial sweet corn farm in Virginia. These results suggest that with optimized spray timing and coverage, HearNPV can provide improved CEW control in cropping systems that observe these best practices. More research is needed to improve application technology and optimize the use of HearNPV in sweet corn.