Pesticides makes bees forget which flowers are most rewarding

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pressreleases_160765Commonly-used pesticides are damaging honey bee brains and their ability to learn, scientists have found.

Two studies from scientists at Newcastle and Dundee Universities have highlighted the negative impact on the bees’ abilities following exposure to a combination of pesticides.

The research has shown that two types of chemicals called neonicotinoids and coumaphos lower brain activity and when combined, the pesticides interfere with the insect’s ability to learn and remember.

Newcastle University’s Dr Geri Wright and Dr Sally Williamson found that a combination of these pesticides made bees forget important associations between floral scent and food rewards.

Their study, published in the Journal of Experimental Biology, established that when bees had been exposed to combinations of these pesticides for four days, as many as 30% of honeybees failed to learn or performed poorly in memory tests. Again, the experiments mimicked levels that could be seen in the wild, this time by feeding a sugar solution mixed with appropriate levels of pesticides.

Dr Wright said: “Pollinators like honeybees, perform sophisticated behaviours while foraging that require them to learn and remember floral traits associated with food. Disruption in this important function has profound implications for honeybee colony survival, because bees that cannot learn will not be able to find food.”

Dr Williamson added: “Our research indicates that bees are able to forage less effectively, they are less able to find and learn and remember and then communicate to their hive mates what the good sources of pollen and nectar are.”

Building on this work, in Nature Communications, Dr Wright and the University of Dundee’s Dr Christopher Connolly investigated the impact on bees’ brains of two common pesticides: pesticides used on crops called neonicotinoid pesticides, and another chemical, coumaphos, that is used in honeybee hives to kill the Varroa mite, a parasitic mite that attacks the honey bee.

The bees’ brains were exposed to pesticides in the lab at levels predicted to occur following exposure in the wild and brain activity was recorded. They found that both types of pesticide target the same area of the bee brain involved in learning, causing a loss of function. If both pesticides were used in combination, the effect was greater.

The study is the first to show that these pesticides have a direct impact on pollinator brain physiology.

Together the researchers expressed concerns about the use of pesticides that target the same neurotransmission pathway in the insect brain and the potential risk of toxicity to non-target insects. Moreover, they said that exposure to different combinations of pesticides that act at this site may increase this risk.

This research is part of the Insect Pollinators Initiative, joint-funded by the Biotechnology and Biological Sciences Research Council, Defra, the Natural Environment Research Council (NERC), the Scottish Government and the Wellcome Trust under the auspices of the Living with Environmental Change (LWEC) partnership.

Reference: J Exp Biol. 2013 Feb 7. Exposure to multiple cholinergic pesticides impairs olfactory learning and memory in honeybees. Williamson SM, Wright GA.

(Newcastle University)

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