Bumblebee Reproductive and Behavioural Responses to Pesticides

Bumblebees are important pollinators and contribute to the pollination of crops and wild plants, however many bumblebee species are in decline. One of the drivers of these declines are pesticides. Bumblebees can be exposed to a variety of different pesticides when foraging in the environment, through matrices such as nectar and pollen. We know very little about how non-insecticidal pesticides can affect bees, these pesticides include fungicides and herbicides. In particular, we know even less regarding how fungicides and herbicides may affect bumblebees, which are important pollinators. The aim of this thesis was to explore how a widely used fungicide (prothioconazole) and herbicide (glyphosate) may affect bumblebees both individually and at the colony level with regards to their behaviour and reproduction, as well as promoting awareness of the importance of this research by highlighting the research gaps in this area. To do this, I conducted a systematic review to identify the knowledge gaps in this research area to inform the rest of this thesis, and highlight its importance to other researchers in this field. I then investigated the interactions of bumblebees with plants dying of herbicide treatment to determine if this was a possible route of exposure, since there was so little research carried out on herbicides. I then investigated the impacts on colony level reproduction, foraging activity and pollen load content, learning and memory, as well as diapause survival and colony initiation. The findings of this thesis indicate that fungicides and herbicides are greatly understudied, particularly in the context of non-Apis bees. I also determine there is not one clear negative affect of these pesticides, and that context is important in observing if there can be behavioural or reproductive implications of glyphosate and prothioconazole. These results demonstrate that whilst I have added to the research gaps in this area, there is still a huge amount of research to be carried out to properly understand the mode of action and the vulnerability of bumblebees to these pesticides, which bumblebees can be frequently exposed to. The findings of this thesis have importance for ecotoxicologists, academics and policy makers by highlighting important areas for future research and promoting awareness that these non-insecticidal substances can also have implications for bees.