Field performance of Cry1F and Vip3A Bt traits under varying western bean cutworm pressure

Western bean cutworm (WBC), Striacosta albicosta (Lepidoptera: Noctuidae), is a native pest of dry bean (Phaseolus vulgaris) and corn (Zea mays) in western Nebraska and has expanded eastward in the past 15 years. Current S. albicosta treatment relies on transgenic Bt corn (Cry1F and Vip3A traits) and chemical insecticides, but recently farmers have reported that moth flights and pest pressure has increased and that these treatments are less effective. This experiment tests the efficacy of transgenic Bt corn with Cry1F or Vip3A  traits under 0, 10, 20 and 30% WBC infestation rates in a field setting. Additionally, we surveyed and collected predatory insects from field plots for PCR gut-content analysis. Feeding trials were also conducted with Coleomegilla maculata and Hippodamia convergens (Coleoptera: Coccinellidae) to see how they responded to S. albicosta eggs and larvae. Our results for infestation pressure were inconclusive due to high larval mortality likely caused by corn growth stage and weather events. Predator surveys revealed four main species in research fields: Orius insidiosus, C. maculata, H. convergens, and Chrysoperla spp. During predator surveys, C. maculata was visually observed feeding on S. albicosta egg masses at least twice. Feeding trials showed that 84.4% of C. maculata fed on WBC prey items while only 36.3% of H. convergens fed on prey items. Gut content analysis will be used to indicate which predators fed on S. albicosta. These results will have implications for using C. maculata and other natural enemies as potential tools for managing S. albicosta infestations in crops.