The impact of managed honeybees and commercial reared bumblebees on pathogens in wild bees

Abstract: Bees are important beneficial insects due to their ability to pollinate our crops and vegetables, as well as being critically important for maintaining wild floral biodiversity. Bees are important from both an economic perspective and an environmental perspective, which highlights the importance of having healthy and sustainable bee populations. The world’s bees share many of the same, or similar, pathogens, which can be transmitted between bees of the same or different species. One concern is that pathogens in imported or managed bees may spill over to native bees, with potentially devastating effects. The aim of this project was to assess if the pathogen distribution in wild bees has any relationship to the distribution of pathogens in managed bees. The pathogens investigated are: Nosema spp., Crithidia spp., Apicystis spp., acute bee paralysis virus (ABPV), slow bee paralysis virus (SBPV) and deformed wing virus (DWV). The study was divided into three separate projects. Super-B project: The goal of this study was to determine if there is a change in the pathogen distribution in wild bees at the same location over three years. Lövsta project: The goal of this study was to determine the pathogen distribution in wild bees in relation to the bee density and distance to honeybee hives. MSB project: The goal of this study was to compare pathogen distribution and abundance in wild bumblebees in relation to the presence or absence of imported bumblebee colonies. These three projects show that there is a relationship between the distribution of pathogens in managed bees and wild bees. During three consecutive years (2015 to 2017), there was an increase in overall pathogen pressure in both honeybees and wild bees, coinciding with an increase of the density of bees in the sampled area. These trends were however different for different pathogens. The distance to honeybee colonies affected the presence and levels of pathogens in wild bees, again in a pathogen-specific manner. Similarly, the effect of imported Bombus terrestris on the pathogen distribution in wild bumblebees, including wild Bombus terrestris, was different for different pathogens. Nosema, Crithidia and ABPV were present at higher levels in the strawberry farm without imported Bombus terrestris, SBPV was higher at the farm with imported Bombus terrestris, while Apicystis and DWV were roughly the same. More investigation is needed on the effect of these pathogens on different bee species and their function pathogen transmission.