Bumblebees threatened by pesticide combination

Monday 22 October 2012

EXPOSURE to two widely used pesticides is threatening the survival of bumblebees, scientists have found.

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Research that aimed to mimic conditions in the countryside, where bees come into contact with numerous chemicals, found the combined effects of the pesticides significantly reduced the success of colonies.

Researchers from Royal Holloway, University of London exposed a common species of bumblebee (Bombus terrestris) to two types of pesticides, a pyrethroid and a neonicotinoid, over four weeks at levels they would encounter in the fields.

Using radio tagging to record the behaviour of bees from 40 colonies, which were allowed to forage outside, the researchers found workers from colonies exposed to the neonicotinoid pesticide were less efficient at foraging, particularly collecting pollen.They were 55% more likely to get lost and not return to the colony than those not exposed to either pesticide, the study published in the journal Nature found.Even though more bees were spending more time foraging, there was less pollen and they spent less time looking after their young, which combined to lead to fewer worker bees being produced.In colonies exposed to the pyrethroid, four times as many bees were found dead in the nest as in the groups that did not come into contact with either chemical.Where the bees were given access to both of the pesticides, they suffered from both higher death rates among the worker bees and less successful foraging, reducing the success of the colony and even making it more likely to fail altogether.Dr Nigel Raine, who led the study, said: "There is an urgent need to understand the reasons behind current bee declines as they are essential pollinators of many agricultural crops and wild flowers."He said pesticide usage was currently approved on tests that examined single pesticides. "However, our evidence shows the risk of exposure to multiple pesticides needs to be considered, as this can seriously affect colony success," he said.

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Bumblebees threatened by pesticide combination

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