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20
gennaio 2011 - Bees facing a poisoned spring - New kind of pesticide,
widely used in UK, may be helping to kill off the world's honeybees
By Michael
McCarthy, Environment Editor - The Independent
link all'articolo su The
Independent
A new
generation of pesticides is making honeybees far more susceptible to disease,
even at tiny doses, and may be a clue to the mysterious colony collapse disorder
that has devastated bees across the world, the US government's leading bee
researcher has found. Yet the discovery has remained unpublished for nearly two
years since it was made by the US Department of Agriculture's Bee Research
Laboratory.
The release of such a finding from the American government's own bee lab would
put a major question mark over the use of neonicotinoid insecticides –
relatively new compounds which mimic the insect-killing properties of nicotine,
and which are increasingly used on crops in the US, Britain and around the
world.
Bayer, the German chemicals giant which developed the insecticides and makes
most of them, insists that they are safe for bees if used properly, but they
have already been widely linked to bee mortality. The US findings raise
questions about the substance used in the bee lab's experiment, imidacloprid,
which was Bayer's top-selling insecticide in 2009, earning the company £510m.
The worry is that neonicotinoids, which are neurotoxins – that is, they attack
the central nervous system – are also "systemic", meaning they are taken up into
every part of the plant which is treated with them, including the pollen and
nectar. This means that bees and other pollinating insects can absorb them and
carry them back to their hives or nests – even if they are not the insecticide's
target species.
In Britain, more than 1.4 million acres were treated with the chemical in 2008,
as part of total neonicotinoid use of more than 2.5 million acres – about a
quarter of Britain's arable cropland.
The American study, led by Dr Jeffrey Pettis, research leader at the US
government bee lab in Beltsville, Maryland, has demonstrated that the insects'
vulnerability to infection is increased by the presence of imidacloprid, even at
the most microscopic doses. Dr Pettis and his team found that increased disease
infection happened even when the levels of the insecticide were so tiny that
they could not subsequently be detected in the bees, although the researchers
knew that they had been dosed with it.
Dr Pettis told The Independent his research had now been put forward for
publication. "[It] was completed almost two years ago but it has been too long
in getting out," he said. "I have submitted my manuscript to a new journal but
cannot give a publication date or share more of this with you at this time."
However, it is known about, because Dr Pettis and a member of his team, Dennis
van Engelsdorp, of Penn State University – both leaders in research focusing on
colony collapse disorder (CCD) – have spoken about it at some length in a film
about bee deaths which has been shown widely in Europe, but not yet in Britain
or the US – although it has been seen by The Independent.
In The Strange Disappearance of The Bees, made by the American film-maker Mark
Daniels, Pettis and van Engelsdorp reveal that they exposed two groups of bees
to the well-known bee disease nosema. One of the groups was also fed tiny doses
of imidacloprid. There was a higher uptake of infection in the bees fed the
insecticide, even though it could not subsequently be detected, which raises the
possibility that such a phenomenon occurring in the wild might be simply
undetectable.
Although the US study remains unpublished, it has been almost exactly replicated
by French researchers at the National Institute for Agricultural Research in
Avignon. They published their study in the journal Environmental Microbiology
and said: "We
demonstrated that the interaction between nosema and a neonicotinoid
(imidacloprid) significantly weakened honeybees."
Neonicotinoids have attracted growing controversy since their introduction by
Bayer in the 1990s, and have been blamed by some beekeepers and environmental
campaigners as a potential cause of CCD, first observed in the US in 2006, in
which billions of worker bees abruptly disappear from their hives.
Between 20 and 40 per cent of American hives have been affected, and CCD has
since been observed in several other countries from France to Taiwan, though it
has not yet been detected in Britain. Although Bayer insists its products are
bee-safe, French and German beekeepers have blamed them for large bee losses.
Neonicotinoids have been banned, to different degrees, in France, Germany, Italy
and Slovenia, although they are freely sold and widely used in the US and
Britain.
In the UK, the Co-op has banned them from farms from which it sources vegetables,
but the Government has rejected appeals from beekeepers and environmentalists
for their use to be suspended as a precaution. This week, however, an Early-Day
Motion was tabled in the Commons by Martin Paton, the Labour MP for Gower,
calling again for the Government to suspend use of the compounds following major
new controversy in the US surrounding Bayer's latest neonicotinoid –
clothianidin – which is increasingly being used in Britain. In November, a
leaked internal document from the US Environmental Protection Agency showed that
it was continuing to license clothianidin, even though its own scientists
reported that the tests Bayer carried out to show the compound was safe were
invalid.
Leading the calls for neonicotinoids to be banned in the Britain is Buglife, the
invertebrate conservation charity, which last year published a review of all the
research done on the chemicals' impact on "non-target" insects such as honeybees
and other pollinators.
Yesterday the Buglife director, Matt Shardlow, said of the Pettis study: "This
new research from America confirms that at very, very low concentrations
neonicotinoid chemicals can make a honeybee vulnerable to fatal disease. If
these pesticides are causing large numbers of honeybees, bumblebees, solitary
bees, hoverflies and moths to get sick and die from diseases they would
otherwise have survived, then neonicotinoid chemicals could be the main cause of
both colony collapse disorder and the loss of wild pollinator populations.
"The weight of evidence against neonicotinoids is becoming irresistible –
Government should act now to ban the risky uses of these toxins."
Bayer insists its neonicotinoids are safe for bees when used properly. Dr Julian
Little, a spokesman for Bayer CropScience UK, said it was difficult for it to
comment on an unpublished study. "It makes it impossible to look at their
methods, it makes it impossible to check whether you can repeat the work, you
don't know where they got the imidacloprid from, you don't know how they gave
that to the bees," he said. But he added: "I'm sure there are some very
interesting effects Dr Pettis has seen in a laboratory, but in reality, when you
get to what's important to everybody, which is what happens in the field, you
don't see these things happening. Bees are very, very important insects to Bayer
CropScience and we recognise their importance."
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