Honeybee visitation to shared flowers increases prevalence in bumblebees.

is a widespread pollinator parasite that commonly infects honeybees and wild pollinators, including bumblebees. Honeybees are highly competent hosts and previous work in experimental flight cages suggests can be transmitted during visitation to shared flowers. However, the relationship between floral visitation in the natural environment and the prevalence of among multiple bee species has not been explored. Here, we analyzed the number and duration of pollinator visits to particular components of squash flowers-including the petals, stamen, and nectary-at six farms in southeastern Michigan, USA. We also determined the prevalence of in honeybees and bumblebees at each site. Our results showed that more honeybee flower contacts and longer duration of contacts with pollen and nectar were linked with greater prevalence in bumblebees. Honeybee visitation patterns appear to have a disproportionately large impact on prevalence in bumblebees even though honeybees are not the most frequent flower visitors. Floral visitation by squash bees or other pollinators was not linked with prevalence in bumblebees. Further, prevalence in honeybees was unaffected by floral visitation behaviors by any pollinator species. These results suggest that honeybee visitation behaviors on shared floral resources may be an important contributor to increased spillover to bumblebees in the field. Understanding how prevalence is influenced by pollinator behavior in the shared floral landscape is critical for reducing parasite spillover into declining wild bee populations.