Honey bee (Apis mellifera) social immunity behaviours: Variance between domestic stocks and effect on chalkbrood (Ascosphaera apis) infection

Chalkbrood is a common fungal disease that affects honey bee (Apis mellifera) brood and has the potential to cause serious economic damage to beekeeping operations, particularly when colonies are already stressed or in conducive environmental conditions. This disease is caused by a heterothallic fungus, Ascosphaera apis, which is distributed worldwide. There is no chemical treatment registered for controlling chalkbrood disease in Canada or the USA, and as such, prevention and control of chalkbrood must be achieved through best management practices that ensure strong, well-nourished colonies. Because A. apis spores are common and the active fungus may be asymptomatic, it is difficult for beekeepers to know the prevalence of the disease in their colonies or beekeeping operation. As such, the use of highly-resistant honey bee stocks capable of self-treating chalkbrood infections are critical to prevent significant disease outbreaks, such as those reported by Canadian beekeepers during blueberry and cranberry pollination. We assessed social immunity traits—namely propolis production and hygienic behaviours—in various stocks of bees and determined their effect on chalkbrood expression while monitoring disease progression in colonies. These findings can be used to advance our knowledge of honey bee social immunity behaviours and to find real-world applications for these traits within the beekeeping and bee breeding industries.