Evaluating trap crop effects on corn earworm (Lepidoptera: Noctuidae) and tobacco budworm (Lepidoptera: Noctuidae)...

Corn earworm (Helicoverpa zea Boddie) and tobacco budworm (Heliothis virescens Fabricius) are economic pests in floral hemp (Cannabis sativa L.). Lepidopteran pest management in floral hemp is challenging due to limited research and heightened regulatory restrictions on chemical control. The utility of cultural control practices has not been well studied for noctuid pests in this system. We conducted controlled cage experiments and a field trial to evaluate sweet corn, sunflower, and ornamental tobacco as potential trap crops and assess the effect of 3 sweet corn planting dates on noctuid pest abundance in hemp. Sweet corn planting date did not affect H. zea larval densities in hemp, although larval abundance on corn varied by planting date. Field populations of H. virescens were more abundant in hemp plots compared to H. zea. In cage choice experiments, H. zea female moths displayed an ovipositional preference toward hemp compared to sunflower and corn; H. virescens had a stronger preference for egg laying on ornamental tobacco compared to hemp and sunflower. Based on our findings, sweet corn has limited potential as an effective trap crop for H. zea management in floral hemp. However, an earlier sweet corn planting date to better synchronize hemp flowering with the corn silk stage may improve trap crop potential. Ornamental tobacco showed promise as an effective trap crop for managing H. virescens in hemp. This study provides foundational research on cultural control strategies to manage critical noctuid pests in floral hemp production in southern Oregon.