* British study says earlier research flawed
* Previous research led to French ban on pesticide
* Pesticide maker Syngenta says new study backs its argument
* Environmentalists say doubts remain about impact on bees
(Adds comment from Syngenta and Friends of the Earth)
By Chris Wickham
LONDON, Sept 21 British scientists have shot
down a study on declining honeybee populations that triggered a
French ban on a pesticide made by Swiss agrochemicals group
France's farm minister Stephane Le Foll withdrew Syngenta's
marketing permit for the pesticide Cruiser OSR in
June, citing evidence of a threat to the country's bees.
But a study by Britain's Food and Environment Research
Agency with the University of Exeter says the results of the
original research were flawed.
The study, published in the journal Science, does not deny
that pesticides could be harmful to individual bees but argues
there is no evidence they cause the collapse of whole colonies.
"We do not yet have definitive evidence of the impact of
these insecticides on honeybees and we should not be making any
decisions on changes to policy on their use," said James
Cresswell, the ecotoxicologist who led the latest study.
The previous research, led by French scientist Mikaël Henry
and published in Science in April, showed the death rate of bees
increased when they drank nectar laced with the neonicotinoid
pesticide, thiamethoxam, the active ingredient in Cruiser OSR.
Neonicotinoids are among the most widely-used agricultural
Henry's work calculated this would cause a bee colony to
collapse completely but Cresswell said the French study seemed
to have used an inappropriately low birth rate, underestimating
the rate at which colonies can recover from the loss of bees.
"They modelled a colony that isn't increasing in size and
what we know is that in springtime when oilseed rape is
blossoming they increase rapidly," Cresswell told Reuters.
The French study has been cited by scientists,
environmentalists and policy-makers as evidence of the impact of
these pesticides on bees, which are declining around the world.
"We know that neonicotinoids affect honeybees, but there is
no evidence that they could cause colony collapse," said
Cresswell. "When we repeated the previous calculation with a
realistic birth rate, the risk of colony collapse under
pesticide exposure disappeared."
Cresswell said Henry's research also used a dosage of
pesticide equivalent to a whole day's intake by the bees, akin
to testing the effect of coffee on people by making them drink
eight cups in one go, rather than spread out over the day.
Henry said he was "perfectly comfortable" with the new
findings, adding in an emailed response to Reuters: "The model
we used predicts a major deviation from the expected colony
dynamics, rather than a collapse per se."
The April paper in Science said exposure to thiamethoxam
"causes high mortality due to homing failure at levels that
could put a colony at risk of collapse".
Syngenta lost a court bid in July to overturn the French ban
on Cruiser OSR, which meant the pesticide was not used for
rapeseed sowing in August and September.
"It's important for us that what we had argued is now
supported by a scientific study," Syngenta France spokesman
Laurent Peron told Reuters. "We are going to use the findings of
this study but it's too early to say in what way."
The French farm ministry declined to comment.
Environmental campaign group Friends of the Earth argued
that sales of the pesticide should be halted while any doubt
about their impact on bees remained.
"Neonicotinoid pesticides cannot be given a clean bill of
health until they have been properly tested for their effect on
all bees, not just honeybees," said campaigner Paul de Zylva.
Cresswell said: "I am definitely not saying that pesticides
are harmless to honeybees, but I think everyone wants to make
decisions based on sound evidence, and our research shows that
the effects of thiamethoxam are not as severe as first thought."
(Additional reporting by Gus Trompiz in Paris; Editing by
Belinda Goldsmith and Pravin Char)