Large-scale study ‘shows neonic pesticides harm bees’ – BBC News

 In Science

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Some honeybee hives exposed to neonicotinoids were at risk of dying off over winter

The most extensive study to date on neonicotinoid pesticides concludes that they harm both honeybees and wild bees.

Researchers said that exposure to the chemicals left honeybee hives less likely to survive over winter, while bumblebees and solitary bees produced fewer queens.

The study spanned 2,000 hectares across the UK, Germany and Hungary and was set up to establish the “real-world” impacts of the pesticides.

The results are published in Science.

Neonicotinoids were placed under a temporary ban in Europe in 2013 after concerns about their impact on bees. The European Commission told the BBC that it intends to put forward a new proposal to further restrict the use of the chemicals.

Prof Richard Pywell, from the Centre for Ecology and Hydrology in Oxfordshire, who carried out the research, told BBC News: “Our findings are a cause for serious concern.

“We’ve shown for the first time negative effects of neonicotinoid-coated seed dressings on honeybees and we’ve also shown similar negative effects on wild bees.

“This is important because many crops globally are insect pollinated and without pollinators we would struggle to produce some foods.”

However, Bayer, a major producer of neonicotinoids which part-funded the study, said the findings were inconclusive and that it remained convinced the pesticides were not bad for bees.

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The experiments assessed oilseed rape grown with and without neonicotinoids

A growing number of studies have found evidence of a link between neonicotinoids and problems for bees.

But there have been questions over whether lab-based research represented what was happening in the wider environment or if the results of field-based studies were merely picking up a simple association between the pesticides and bee impacts rather than direct causation.

“There was a need to undertake a large-scale, realistic experiment to represent the effects of neonicotinoids on pollinators in the real world,” said Prof Pywell.

The pan-European trials took place across 33 sites.

Bees were exposed to winter-sown oilseed rape that had been treated with two different types of neonicotinoids – Bayer’s clothianidin and Syngenta’s thiamethoxam – as well as untreated oilseed rape.

For bumblebees and solitary bees, the researchers said that in the UK, Hungary and Germany, higher concentrations of neonicotinoid residues found in nests resulted in fewer queens.

The scientists also found a type of neonicotinoid called imidacloprid in the wild bee nests. This pesticide was not used in the study, and the team said its presence suggested that despite the 2013 ban, the chemicals were lingering in the environment.

For honeybees, the scientists concluded that in the UK and Hungary, exposure to neonicotinoids meant that hives were at risk of dying out over the winter.

Prof Pywell said: “In the UK, we had high hive mortality.”

In Hungary, colonies fell by 24% over winter.

However in Germany, the scientists found there were no harmful effects on overwintering honeybees.

They believe this may be because bee diseases are less prevalent in Germany and the insects also have a wider range of flowers to forage on.

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Bumblebees were less likely to produce queens after exposure to the pesticides

Commenting on the research that it had part-funded, Syngenta said the data was valuable but variable.

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