Even low exposure to pesticides can seriously disrupt foraging behavior in bees. New research reveals that exposure to pesticides significantly alters flower choices, learning abilities and ability to extract nectar and pollen in bumblebees.
While bumblebees exposed to a realistic level of neonicotinoid insecticide collected more pollen, lead researcher Dara Stanley, of Royal Holloway University of London, found that they took significantly longer than unexposed bees to do so.
"We found that chronic exposure to field-realistic levels of thiamethoxam altered the interactions between bumblebees and morphologically complex wildflowers. First, a higher proportion of bees that were released from pesticide-treated colonies became foragers in comparison to control colonies. Of these foragers, bees exposed to pesticide visited more L. corniculatus flowers, showed a trend towards a preference for this species on their first flower visit and collected more pollen," researchers wrote in the study.
"However, although bees exposed to pesticide learnt to manipulate flowers sooner, control bees learnt to manipulate flowers after fewer flower visits than pesticide-exposed bees, and also visited a higher proportion of T. repens flowers," they added.
Unexposed bees were also quicker at learning how to manipulate flowers after significantly fewer visits than their exposed counterparts, according to Stanley.
"Bumblebees exposed to pesticide initially foraged faster and collected more pollen. However unexposed bees may be investing more time and energy in learning. Our findings have important implications for society and the economy as pollinating insects are vital to support agriculture and wild plant biodiversity," Stanley explained in a news release.
"Bees rely on learning to locate flowers, track their profitability and work out how best to efficiently extract nectar and pollen," added senior study author Nigel Raine, environmental sciences professor of the University of Guelph. "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," said Raine, who is also the Rebanks Family Chair in Pollinator Conservation the University of Guelph.
Past research revealed that honeybees exposed to neonicotinoid pesticides experienced significant changes in brain regions linked to learning and memory. Researchers said the latest findings are worrying because bees and other insects are an important part of global food security and biodiversity.
Raine said the latest study highlights the need for more field-realistic research on how pesticides affect bee behavior.
"Our results suggest that current levels of pesticide exposure could be significantly affecting how bees are interacting with wild plants, and impairing the crucial pollination services they provide that support healthy ecosystem function," he concluded.
The latest findings were published in the journal Functional Ecology.