Abstract/Summary

Bees are the most dominant pollinators worldwide, providing many monetary and non-monetary benefits to society. However, wild bee declines and honeybee colony losses are reported in many regions of the world. Several pressures are responsible for these declines, including land use change, pesticides, and diseases, which can occur simultaneously and interact with each other. However, many knowledge gaps on the impacts of multiple pressures on pollinators remain. Here, I focus on managed Apis mellifera and Bombus terrestris and investigate: (a) the interactive effects of land cover and pesticides on bee health, activity, and crop yield using a large-scale fieldwork; (b) the impact of the new insecticide sulfoxaflor, the pathogen Crithidia bombi, and their interaction on bee behaviour and pollination, using a semi-field experiment in flight cages; and (c) beekeepers’ perceptions of the Bee Health Card, a tool under development that can help tackle health issues in beehives, using surveys involving 7 European countries. My findings indicate that higher proportions of cropland and lower proportions of woodland in the landscape favour Bombus terrestris colony growth in apple orchards, while a higher honeybee activity is linked to higher proportions of woodland. In oilseed rape fields, both B. terrestris colony growth and social bee activity are increased by higher fungicide and herbicide pressures. Moreover, I show that sulfoxaflor and Crithidia bombi, individually and in combination, do not affect the behaviour or pollination by Bombus terrestris. Finally, I observe that beekeepers recognise the opportunity offered by the Bee Health Card, and that the confidence in its effectiveness is key to its adoption. Cost is a barrier when economic incentives are not available, but environmental benefits may help increase the willingness to use the tool in such cases. I conclude that bees face several interacting pressures varying across species, and that the Bee Health Card may be useful in detecting and addressing such pressures, benefitting both wild and managed bees.