French researchers say they have found the ‘missing link’ behind the different conclusions reached by tests on and in the laboratory and in the field.

The National Institute for Agricultural Research (INRA) scientists say neonicotinoid insecticides can harm individual although whole colonies can alter their behaviour, producing more worker bees to make up for the high losses in response to exposure.

The European Commission imposed its ban in December 2013 on three neonicotinoids that were used as seed dressing on -attractive crops, such as oilseed rape, due to their perceived harmful effect on bees, and will review the ban next month.

Reporting in the Royal Society journal Proceedings B, the French scientists were looking at the impacts of one neonic, thiamethoxam (sold as Cruiser OSR), at the behest of France’s food safety agency ANSES. However, bees were also “unexpectedly” exposed to imidacloprid, another neonicotinoid (which was banned from use on sunflowers in France in 1999 ands has never been used on OSR in the country).

Their findings suggest that the pesticides do harm honeybees (bees foraging in crops treated with neonics died off at a quicker rate), but that whole colonies alter their behaviour, producing more worker bees to make up for the high losses in response to exposure. However, this process delays the production of male drones in the colonies, whose job is to breed.

Though those who, like the UK government, reject the Commission’s neonic restrictions have welcomed Wednesday’s report, claiming that results suggest bee colonies are able to recover in the wild, independent scientists have pointed out that other insect pollinators cannot rely on such buffers to protect them from harm.

The researchers behind the new study stress that, given the “strong and unprecedented link” between evidence of harm to bees in lab studies and their findings in the field, “It is… urgent that risk assessors take into account the scientific evidence for behavioural disorders triggered by trace levels of neonicotinoids.”

Furthermore, the re-evaluation in March this year of an inconclusive Defra-funded study, which was first published without peer review in 2013, ahead of the Commission’s decision to restrict use of certain neonics, uncovered evidence of harm to bee colonies where research agency FERA found none.



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