Bayer CropScience has dismissed the findings of a US report that linked neonicotinoid pesticides to a decline in bee health.

The report, by researchers at Harvard University, claimed that using two Bayer neonicotinoids significantly harmed honeybee colonies over winter, especially during cold seasons.

The study in Massachusetts suggested the use of two neonicotinoids – imidacloprid and clothianidin – led to bees abandoning their hives and dying.

But Bayer has rejected the findings of the research as “totally unrepresentative of what is happening in agriculture”.

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Dr Julian Little, spokesman for Bayer CropScience UK, explained: “The researchers were feeding honeybees with dose rates at 10, possibly nearer 100, times what they would normally encounter in the field.

“Not only were the doses really high, they were also given over 13 consecutive weeks.

“The chances of bees ever coming into contact with these sort of levels over that period of time is unrealistic – and for a whole colony, no chance.”

Dr Little added that the research was “really disappointing” as it was “so far away from the reality in the field, it was untrue”.

“The authors suggest that it is field-realistic. Quite simply, it isn’t,” he said.

Bayer has insisted that the EU’s ban on neonicotinoids linked to a decline in bees is unjustified.

It said other factors, including loss of habitats and climate change, were to blame. Globally, it has singled out the parasitic Varroa mite as the main culprit.