A study from the departments of Chemistry and Zoology at the University of Otago has revealed that Honeybees can suffer severe learning and memory deficits after consuming small amounts of the pesticide, Chlorpyrifos.
In their study, researchers collected bees from 51 hives across 17 locations in Otago, southern New Zealand, in order to measure their Chlorpyrifos levels. Low levels of pesticide were detected in bees at three of the 17 sites, as well as in six of the 51 hives that were analysed.
Scientists were not surprised by the discovery of Chlorpyfiros, since Associate Professor Kim Hageman and her team found traces of the pesticide in the air, water and plant samples back in 2013. Chlorpyfiros was even detectable in non-sprayed areas since the chemical is highly volatile and can travel long distances.
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In a controlled environment scientists then fed bees a similar amount of the pesticide, which is used around the world to keep insects away from crops, to see how it would affect their performance in a learning test.
According to Dr Elodie Urlacher, lead author of the study, researchers found that bees who had ingested Chlorpyfiros were worse at learning different types of odours, and were also much less effective at recalling odours later on, even though the amount they had consumed was considered to be ‘safe’.
“For example, the dosed bees were less likely to respond specifically to an odour that was previously rewarded,” said Dr Urlacher. “As Honeybees rely on such memory mechanisms to target flowers, Chlorpyfiros exposure may be stunting their effectiveness as nectar foragers and pollinators.”
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The study has allowed researchers to identify the threshold for a lethal dose of Chlorpyfiros in terms of odour-learning and recall performance, which is 50 picograms of ingested Chlorpyfiros per bee, according to Urlacher.
“This amount is thousands of times lower than the lethal dose of pure Chlorpyfiros, which is around 100 billionths of a gram. Also, it is in the low range of the levels we measured in bees in the field.
“Our findings raise some challenging questions about regulating this pesticide’s use. It’s now clear that it is not just lethal effects on bees that need to be taken into account, but also the serious sub-lethal ones at minute doses,” Urlacher concludes.
The research has been published in the Journal of Chemical Ecology.
Additional reporting by University of Otago.
Image via Librestock.