Local and Landscape-Scale Features Influence Bumble Bee (Hymenoptera: Apidae) Bycatch in Bertha Armyworm Mamestra configurata (Lepidoptera: Noctuidae) Pheromone-Baited Monitoring Traps

The bertha armyworm (BAW) Mamestra configurata Walker is a significant pest of canola Brassica napus L. (Brassicales: Brassicaceae) in western Canada. Its activity is monitored through a large network of pheromone-baited monitoring traps as a part of the Prairie Pest Monitoring Network across the Canadian Prairies. The unintentional bycatch of bee pollinators in pheromone-baited traps targeting moth pests occurs in many agroecosystems and may have repercussions for biodiversity and pollination services of wild plants and managed crops. We conducted field experiments to determine the abundance and diversity of bees attracted to green-colored BAW pheromone-baited traps across the canola growing regions of Alberta, Canada. A higher species diversity and more bumble bees were captured in BAW pheromone-baited than in unbaited control traps. Bombus rufocinctus Cresson (Hymenoptera: Apidae) was the most commonly captured species. Few other wild bees or honey bees Apis mellifera L. (Hymenoptera: Apidae) were captured during this study. Additionally, we evaluated the influence of local and landscape-level habitat features on bee bycatch. Local flowering plant abundance improved overall model fit but did not directly impact bee bycatch. The proportion of natural and seminatural habitat, and especially forested area, in the area surrounding monitoring traps affected bee bycatch. Both local and landscape-scale factors were important in this study and often have combined effects on bee communities. This study provides recommendations to reduce the bycatch of beneficial bee pollinators in a large-scale pheromone-baited monitoring network.

Role of enhancin in Mamestra configurata nucleopolyhedrovirus virulence: selective degradation of host peritrophic matrix proteins

To infect per os, baculovirus virions cross the peritrophic matrix (PM) to reach the midgut epithelium. Insect intestinal mucins (IIMs) are PM proteins that protect the PM and aid passage of the food bolus through the gut. Some baculoviruses, including Mamestra configurata nucleopolyhedrovirus (MacoNPV-A), encode metalloproteases, known as enhancins, that facilitate infection by degrading IIMs. We examined the interaction between MacoNPV-A enhancin and M. configurata IIMs both in vivo and in vitro. Per os inoculation of M. configurata larvae with MacoNPV-A occlusion bodies (OBs) resulted in the degradation of McIIM4 within 4 h of OB ingestion, while McIIM2 was unaffected. The PM recovered by 8 h post-inoculation. To investigate whether enhancin was responsible for the degradation of IIM, a recombinant Autographa californica multiple nucleopolyhedrovirus expressing MacoNPV enhancin (AcMNPV-enMP2) was constructed. Enhancin was found to be a component of occlusion-derived virions in AcMNPV-enMP2 and MacoNPV-A. In in vitro assays, McIIM4 was degraded after MacoNPV-A and AcMNPV-enMP2 treatments. Degradation of McIIM4 was inhibited by EDTA, a metalloprotease inhibitor, indicating that the degradation was due to enhancin activity. Thus, MacoNPV-A enhancin is able to degrade major structural PM proteins, but exhibits target substrate specificity.