European foulbrood may affect availability of honey bee colonies in pollination-deficient blueberry farms

Blueberries are Canada’s top fruit crop export, valued at $552 million in 2019. British Columbia (BC) produces most of Canadian cultivated highbush blueberries, which are primarily pollinated by honey bees from BC and Alberta. BC blueberry crops experience limited pollination, which is a concern for producers. At the same time, beekeepers have reported a decline in colony health, observing an increase in European foulbrood (EFB) in blueberry-pollinating colonies. We investigated bee health in blueberry-pollinating colonies, because decreases in post-pollination health status can affect beekeepers’ decisions on future pollination contracts.
We examined one blueberry-pollinating site and one wild forage-pollinating site across three time points (start, end, and post-blueberry pollination). We observed a greater increase in EFB-like symptoms in the blueberry-pollination colonies. Laboratory analysis incorporated the novel technique of droplet digital PCR to obtain absolute quantitation of Melissococcus plutonius, the etiological agent of EFB, in nurse bees. We found that colonies can have M. plutonius infections with variable levels of EFB symptoms. Levels of Varroa destructor and Nosema spp. did not seem to be affected by forage type. We are also identifying chemical compounds in honey and bee bread obtained from both groups of colonies.
An increase in EFB symptoms following blueberry pollination may affect colonies available for pollination services, and impose further challenges to pollination-deficient blueberry farms. Our increased understanding of the variables affecting bee health and pollination services will help ensure the sustainability of agricultural crop systems that depend on managed pollinators for optimal crop production.