Non‐neonicotinoid pesticides impact bumblebee activity and pollen provisioning

Bees are essential pollinators of crops and wild plants and their ability to forage and pollinate are key aspects of their behaviour. Bee populations are under threat, with the use of insecticides a contributing factor. Most research has focused on neonicotinoid insecticides and bee mortality, and little is known about impacts on bee foraging and delivery of pollination services. However, other insecticide classes, such as organophosphates and pyrethroids, are increasingly used globally, but little is known about how these widely used substances may impact bees, particularly non‐honeybees. We exposed bumblebee Bombus terrestris colonies to field‐relevant doses of a pyrethroid (lambda‐cyhalothrin) and an organophosphate (dimethoate) and investigated sublethal effects on behaviour at the individual and colony level, in addition to pollination service delivery under semi‐field conditions. We show, for the first time, that exposure to these chemicals impacts the activity and pollen provisioning of bumblebee Bombus terrestris audax colonies, while no short‐term effects on flower handling behaviour or pollination service delivery were detected. We found that colonies exposed to dimethoate were less active, with 67% fewer bees leaving the colony to forage than control colonies, and of those that returned, 92% fewer returned pollen provisions to the nest. Colonies exposed to lambda‐cyhalothrin did not differ in activity; however, 62% fewer of these bees returned with pollen provisions. Policy implications. These findings give important insights into how exposure to different classes of insecticides could impact bumblebee activity and their provision of pollen required for colony development. With a focus on neonicotinoids in terms of policy changes regarding insecticides and bees, we show that other insecticide classes should also be re‐examined in relation to their potential risks for pollinators. We confirm the need to improve risk assessment of insecticides to assess sublethal effects, include non‐honeybee species in risk assessment processes and also consider key behaviours such as foraging and interactions with plants. These findings give important insights into how exposure to different classes of insecticides could impact bumblebee activity and their provision of pollen required for colony development. With a focus on neonicotinoids in terms of policy changes regarding insecticides and bees, we show that other insecticide classes should also be re‐examined