Mushroom mycelium as a pathogen reducing additive to commercial bumble bee diet

Managed bumble bees transmit pathogens they acquire in commercial rearing facilities to wild bumble bee communities, which contributes to population declines. Therefore, it is important to find ways to eliminate pathogens from bumble bee rearing facilities and commercial colonies to reduce pathogen transmission to native bee communities. Previous research in honey bees found that mycelia extract from Reshi mushrooms significantly reduced Deformed Wing Virus and Lake Sinai Virus both in laboratory and field settings. As many fungi, including Pleurotus columbinus, produce wordantimicrobial chemicals and support immunity, these pathogen-reducing results may carry over to managed bumble bee colonies and provide a way to reduce pathogens in rearing facilities. It has also been shown that bumble bees given pollen with higher nutritional contents have more immune gene expression and stronger immune responses. As we have shown that P. columbinus mycelium may be a beneficial nutritional additive to B. impatiens’ diet, we can hypothesize that increased nutritional content and mycelial antimicrobial compounds may aid bumble bee immune responses. To test our hypotheses, we will create microcolonies of Bombus impatiens workers infected with the common bumble bee pathogen Crithidia bombi and provide them with pollen provisions containing a 1% concentration of dried P. columbinus mycelium or a mycelium-free control. Pathogen loads in workers and adult offspring, the number of offspring produced, adult offspring body size and weight, and internal fat, protein, and carbohydrate content of adult male offspring will be obtained for each microcolony.