Evaluating trap crops for managing Helicoverpa zea and Heliothis virescens in floral hemp systems

Corn earworm (Helicoverpa zea) is a major pest of floral hemp, where its larval feeding causes significant damage to flower buds and reduces flower yield. Currently, few non-pesticide options exist to manage this pest. In the field, we tested the sweet corn as a potential trap crop, using different planting times (early, mid-season, and late) to see if synchronizing corn flowering with hemp could help draw corn earworm moths away from the crop. However, field results did not provide evidence indicating the value of this trap crop. Field observations, however, resulted in an interesting find: tobacco budworm (Heliothis virescens) caused extensive damage to flower buds. Thus, additional greenhouse trials were conducted to determine the relative host preference for these two pests. We evaluated oviposition behavior and plant attractiveness using two- and three-choice assays for both H. zea and H. virescens. For corn earworm, there was clear preference for hemp over corn, indicating that floral traits in hemp contribute to relatively strong attraction over corn. Tobacco budworm exhibited preference for Nicotiana spp. over hemp. Together these data, highlight the importance of understanding host plant traits in developing non-chemical management strategies for hemp.