The effect of hygienic behavior, viral co-infection and blueberry pollination on the development of European foulbrood in honey bees in Michigan

European foulbrood (EFB) has been an increasing problem for Michigan beekeepers. Here we examine the role that blueberry pollination, hygienic behavior, and viral co-infection play in the development of EFB. In May of 2020, 60 queen right hives were selected from a commercial beekeeping operation in Michigan and split into two locations: in blueberry fields for pollination or a distant holding yard, away from blueberries. Hygienic testing was performed on each hive and workers were collected for viral testing and hive health metrics and EFB disease status were gathered three times over the season. We found high levels of viral co-infection, with no clear links to health outcomes. No statistically significant difference was found in the development of clinical disease between the two groups with 61% (17/28) of the colonies in the holding yard developing moderate to severe disease over the course of the season compared with 69% (20/29) of those in blueberry pollination. No relationship was found between hygienic behavior and colony health. This suggests that blueberry pollination is likely not an important factor in the development of European foulbrood and hygienic behavior is not important in preventing the development of this disease.