A new class of pesticides used to replace neonicotinoids could be just as harmful to crop-pollinating bees.
That's according to researchers from the Royal Holloway University of London, who claimed following experiments that the ability of bumblebees to reproduce - and the rate at which their colonies grow - were compromised by the new chemical.
The new class of insecticides are based on the chemical sulfoximine, instead of neonicotinoids, which have become widely used in recent years. However, it has also been claimed that neonicotinoids are behind a significant decline in bee numbers and colony collapses in recent years.
Reported in the journal Nature, the findings show that colonies exposed to low doses of the pesticide in the lab yielded significantly less workers and half as many reproductive males after the bees were transferred to a field setting.
"Our results show that sulfoxaflor can have a negative impact on the reproductive output of bumblebee colonies," said Harry Siviter, lead author of the paper and researcher at Royal Holloway University of London.
The problem with sulfoxaflor is that while it doesn't kill bees directly, it appears to affect the immune system or their ability to reproduce - just as it is strongly believed that neonicotinoids do.
The researchers have called for regulatory bodies to look at the non-lethal effects insecticides might have on bees before issuing a licence.
They have suggested that, in order to keep bees safe as a species, we need to know more about the levels of insecticides the insects can tolerate in the wild so that the level of risk can be more accurately assessed.
Dr Ellouise Leadbeater of Royal Holloway, University of London, added: "Our study highlights that stressors that do not directly kill bees can still have damaging effects further down the line, because the health of the colony depends on the health of its workforce."
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