Assessing the impact of bycatch on Bombus griseocollis colony growth and development

Insect traps use visual and olfactory cues to attract target pests; however, they vary in their specificity and often unintentionally capture non-target insects (bycatch), including Bombus. Bycatch contributes to population declines in marine wildlife and results in negative impacts to associated ecosystems. Therefore, it is possible that bycatch negatively impacts Bombus populations and pollination services; however, this relationship has not yet been studied. Our objective was to quantify the impact of bycatch on Bombus griseocollis colony growth and development. Colonies were evaluated under four treatments: (i) marked B. griseocollis colonies paired with multicolored plastic bucket traps, (ii) marked colonies paired with traps and pheromone lures for Helicoverpa armigera, (iii) traps and lures (but no Bombus colonies), and (iv) marked colonies with no trap and no lure. This experiment took place within corn and vegetable fields in Utah in 2019 and 2020. Colonies were weighed and worker activity was measured weekly and trap contents were collected biweekly from July to September. Preliminary results from 2019 show no differences among treatments in relation to cumulative weight change or average worker activity for each colony based on a one-way random effects analysis of variance. However, more species of resident Bombus were collected in traps with lures. We are currently in the process of determining if the B. griseocollis collected in traps were from our released colony or were residents within the environment. Future work will include the development of an ecosystem service model to determine bycatch risk to pollination services.