Bees are important pollinators, though, recent evidence suggests some species of bumble bees (Hymenoptera, Apidae, Bombini, Bombus Latreille) are declining in parts of their ranges due to a combination of drivers such as climate change, pesticide use, habitat loss, competition for resources and pathogens acting upon the bees at once. A relatively new and important area of gut microbial research, the fungal and bacterial gut community members, could offer insight on why some species of bumble bees are declining while others remain stable. In this thesis, I use a combination of field and molecular methods to investigate aspects of bumble bee health in Saskatchewan, Canada, including species occurrence and pathogen incidence and explore microbial associations with known and potential pathogens. The second chapter explores the need for a bumble bee monitoring program in Saskatchewan and how standardization compares to non-standardized survey methods. I compared bumble bee occurrence data from four datasets in terms of sampling effort over time and how properties of each dataset influenced species conservation assessments. The Palmier dataset was a single collection event in 2018 using a standardized survey methods. The Royal Saskatchewan Museum (RSM) and Global Biodiversity Information Facility (GBIF) datasets represented specimens collected with unstandardized collection events over decades. The iNaturalist dataset contained citizen science observations. The Palmier dataset was the largest of the four datasets and despite the single collection event, species richness in the Palmier dataset was comparable to the RSM and GBIF datasets. The iNaturalist dataset was biased to locations with higher population density and overrepresented species at-risk compared to the Palmier, RSM and GBIF datasets. The third chapter (previously published) documents the first occurrences of the Common Eastern Bumble Bee (B. impatiens), a managed species that is not native to the Canadian prairies, recorded from southeastern Alberta. The fourth chapter (also previously published) documents the first Canadian occurrence of a recently characterized trypanosomatid bumble bee pathogen, Crithidia expoeki, in native Saskatchewan bumble bees. The fifth chapter explores the fungal and bacterial gut communities of bumble bees and their associations with common bee pathogens. The results indicate that pathogens cause dysbiosis, or imbalance of microbial communities in bumble bees. A differential abundance analysis revealed significantly enriched and depleted taxa in bees testing positive for specific pathogens. The results from this study can be used to compare microbial strain level differences across geographic landscapes over time. The sixth chapter investigates a novel yeast association and swollen proventriculus in the digestive tract of at-risk bumble bee species across Canada. It was discovered that the swollen proventriculus morphology occurred only in males in the subgenus Bombus, a taxon in which the majority of North American species are at-risk. Classic culturing methods and Sanger sequencing revealed that bumble bees with a swollen proventriculus harboured distinct yeast communities in high numbers. Using 16S rRNA sequencing, I also found higher abundances of lactic acid bacteria and Gillimella bacteria in male bumble bees with a swollen proventriculus compared to bumble bees of both sexes without.