A naturally occurring baculovirus (Helicoverpa zea nucleopolyhedrovirus) with the commercial name of Heligen® was registered in Kentucky under FIFRA Section 24(c) (Heligen 24c KY190041 SLN Acknowledgement Letter_20190925). This is a highly specific virus used to control corn earworm (Helicoverpa zea) and budworms (Heliothis virescens). This baculovirus needs to be ingested by the caterpillar to be infective. Once ingested, the baculovirus releases occlusion bodies in the caterpillar’s midgut that interact with the membrane of microvillar epithelial cells. As the infection progress, the larva’s body darkens and liquefies. This product may help industrial hemp growers as they are being affected by an outbreak of corn earworms.
The effectiveness of Heligen® is dependent on larval size, environmental conditions, application, and the feeding behavior of the pest. Infected larvae can take up to 8 days to die, although feeding activity is greatly reduced within 1 to 3 days post-infection, depending on larvae size. Temperature ranges from 65°F to 95°F are ideal for infectivity by Heligen®. Also, good coverage is important as the product needs to be ingested to be effective. Poor results may be expected if Heligen does not reach actively feeding larvae.
Heligen® can be used at 1.0 to 2.4 fl. oz. per acre. Use the higher application rate when flowers, seeds, or economic parts of the crop are present, under high pest pressure conditions, or to control 3rd instar larvae. Use the lower application rate during vegetative stages of crop production. Re-apply Heligen® at 7-day intervals during periods of continual pest infestation or as a preventive strategy.
In order to use Heligen®on hemp, the applicator will need to have a copy of the Heligen® 24(c) label, be a certified applicator, and check with their hemp buyer to make sure this is acceptable. The label for Heligen®can be accessed here: Heligen_24c_Label 2019.
By Raul T. Villanueva and Ric Bessin, Extension Entomologists