Bumble bee pathogen prevalence is determined by host species

Bumble bees (Order Hymenoptera) are important pollinators of economically significant crops. In the past 20 years, there has been a decline in several North American species. Several causal factors contributing to bumble bee decline have been identified, including habitat loss, pesticides, and pathogens. Pathogens, particularly those originating from commercial colonies, are an immediate concern for conservationists. The effects of land cover on the distribution of bumble bee pathogen prevalence in the U.S.A is largely unknown. Madison, WI is a large metropolitan area and is bordered by suburbs, exurbs, agriculture, and forested areas. During the summers of 2019 and 2020, 2,094 bees were collected from 20 urban and agricultural sites. Each bee was screened for the microparasites Vairimorpha bombi, Crithidia bombi, Crithidia expoeki, and Apicystis bombi using a multiplex PCR panel. Conopid flies (Order Diptera) and mermithid nematodes (Order Mermithida), both large endoparasitoids, were also found. Bombus impatiens, the most abundant species, had the highest pathogen prevalence and the most prevalent pathogen in this species was Apicystis bombi.