Flower plantings support wild bees and may also mitigate pesticide effects on reproduction

Sustainable agriculture relies on pollinators, and wild bees benefit many crops through increased yield. However, the combined exposure to pesticides and loss of flower resources, driven by agricultural intensification, contribute to declining diversity and abundance of many bee taxa. Flower plantings along the margins of agricultural fields offer diverse food resources not directly treated with pesticides. To investigate the potential of flower plantings to mitigate bee pesticide exposure effects and support bee reproduction, we selected replicated sites where half contained a flower planting. We assessed solitary bee (Osmia lignaria) and bumble bee (Bombus vosnesenskii) nesting and reproduction throughout the season in these landscapes. We also quantified local and landscape flower availability and used bee-collected pollen to determine forage resource use and pesticide exposure. Flower plantings, and the local flower resources they provided, supported solitary bee reproduction. Bumble bee reproduction was more strongly related to landscape-wide flower resources. Flower plantings did not reduce bee pesticide exposure, and their flowers were a source of pesticide exposure particularly for the solitary bee. However, local flower resources mitigated negative pesticide effects on bumble bee reproduction. There is an urgent need to find solutions to mitigate negative effects of pesticide use and loss of flowers associated with agricultural intensification. Our findings point towards flower plantings as a potential solution that merits further investigation on the balance between forage benefits and added pesticide exposure.