Low levels of pesticides can impact the foraging behaviour of bumblebees on wild flowers, changing their floral preferences and hindering their ability to learn the skills needed to extract nectar and pollen, according to a paper in Functional Ecology, which claims it is the first to explore how pesticides may impact the ability of bumblebees to forage from common wild flowers that have complex shapes such as white clover and bird’s foot trefoil.
Bees and other insects pollinate many of the world’s important food crops and wild plants, and some believe they have been threatened in recent years. As such, there is an increasing need for field-realistic research into the impact of pesticides on bumblebees and other wild pollinators. Currently, there is reliance on anecdotal evidence of die-offs, at a time when amateur beekeeping has become popular. Meanwhile, some countries which use the primary class of pesticide blamed by environmental activists, called neonicotinoids, have shown no die-offs at all.
Yet the obvious case, parasites and climate, get little traction outside scientists with expert knowledge. And a team of ecologists takes the same tacks, finding that bumblebees exposed to a realistic level of a neonicotinoid insecticide (thiamethoxam) collected more pollen but took longer to do so than control bees. Pesticide-exposed bees also chose to forage from a different flower in comparison to control bees.
Professor Nigel Raine, University of Guelph (Canada) and Visiting Professor in Ecology at Royal Holloway, said, “Bees rely on learning to locate flowers, track their profitability and work-out how best to efficiently extract nectar and pollen. If exposure to low levels of pesticide affects their ability to learn, bees may struggle to collect food and impair the essential pollination services they provide to both crops and wild plants.”
Previous studies have found that exposure to neonicotinoid pesticides can cause changes in the brain, more specifically in the areas associated with learning and memory in honeybees.
In this new study, the researchers found that, while bumblebees exposed to pesticides collected more pollen than control bees, control bees were able to learn how to manipulate these complex flowers after fewer visits.