Neonicotinoid pesticide exposure impairs crop pollination services provided by bumblebees

Abstract

Recent concern over global pollinator declines has led to considerable research on the effects of pesticides on bees ^{1- 5} . Although pesticides are typically not encountered at lethal levels in the field, there is growing evidence indicating that exposure to field-realistic levels can have sub-lethal effects on bees affecting their foraging behaviour ^{1, 6, 7} , homing ability ^{8, 9} and reproductive success ^{2, 5} . Bees are essential for the pollination of a wide variety of crops and the majority of wild flowering plants ^{10- 12} , but until now research on pesticide impacts has been limited to direct effects on bees themselves and not on the pollination services they provide. Here we show the first evidence that pesticide exposure can reduce the pollination services bumblebees deliver to apples, a crop of global economic importance. Colonies exposed to a neonicotinoid pesticide provided lower visitation rates to apple trees and collected pollen less often. Most importantly these pesticide exposed colonies produced apples containing fewer seeds demonstrating a reduced delivery of pollination services. Our results also suggest reduced pollination service delivery is not due to pesticide-induced changes in individual bee behaviour but most likely due to impacts at the colony level. These findings show that pesticide exposure can impair the ability of bees to provide pollination services, with important implications for both the sustained delivery of stable crop yields and the function of natural ecosystems.