Chronic exposure to a neonicotinoid pesticide alters the interactions between bumblebees and wild plants

Abstract

Summary Insect pollinators are essential for both the production of a large proportion of world crops and the health of natural ecosystems. As important pollinators, bumblebees must learn to forage on flowers to feed both themselves and provision their colonies.Increased use of pesticides has caused concern over sublethal effects on bees, such as impacts on reproduction or learning ability. However, little is known about how sublethal exposure to field‐realistic levels of pesticide might affect the ability of bees to visit and manipulate flowers.We observed the behaviour of individual bumblebees from colonies chronically exposed to a neonicotinoid pesticide (10 ppb thiamethoxam) or control solutions foraging for the first time on an array of morphologically complex wildflowers (Lotus corniculatus and Trifolium repens) in an outdoor flight arena.We found that more bees released from pesticide‐treated colonies became foragers, and that they visited more L. corniculatus flowers than controls. Interestingly, bees exposed to pesticide collected pollen more often than controls, but control bees learnt to handle flowers efficiently after fewer learning visits than bees exposed to pesticide. There were also different initial floral preferences of our treatment groups; control bees visited a higher proportion of T. repens flowers, and bees exposed to pesticide were more likely to choose L. corniculatus on their first visit.Our results suggest that the foraging behaviour of bumblebees on real flowers can be altered by sublethal exposure to field‐realistic levels of pesticide. This has implications for the foraging success and persistence of bumblebee colonies, but perhaps more importantly for the interactions between wild plants and flower‐visiting insects and ability of bees to deliver the crucial pollination services to plants necessary for ecosystem functioning.

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 2: impacts on organisms and ecosystems

“…Bees exposed to thiamethoxam learned to manipulate flowers faster but after more visits (Stanley and Raine 2016). These results suggest that exposure of bees to sublethal concentrations of neonicotinoids may alter their function as pollinators, possibly favoring some plant species over others, with potential implications for both crop production and wildflower reproductive success.…”

Ecological intensification to mitigate impacts of conventional intensive land use on pollinators and pollination

“…The role of insecticides in affecting pollination services is unclear, but there is some new experimental evidence that insecticides affect floral preference and thus can modify the likelihood of delivery of pollination services to crop and wild plants by altering bee behaviour (Stanley et al . ; Stanley & Raine ).…”

Bee Community of Commercial Potato Fields in Michigan and Bombus impatiens Visitation to Neonicotinoid-Treated Potato Plants

“…Although not studied in potato specifically, pesticides can affect bumblebee physiology and behavior. For example, bumblebee foraging behavior was altered by chronic exposure to a neonicotinoid insecticide [19,20] and their fecundity and colony growth was also negatively impacted by neonicotinoid consumption [21,22,23]. While these studies suggest bees may be negatively affected by neonicotinoids, other work suggests that realistic exposures to neonicotinoids in the field do not negatively affect bees and that sublethal effects do not necessarily result in lasting colony effects, especially if pesticide-free alternative forage is available [24,25,26,27,28,29].…”