Chemical death sentence for bees

Photo / Sarah Ivey

A new generation of pesticides is making honeybees far more susceptible to disease and may be a clue to the mysterious colony collapses that have devastated bees around the world.

Yet this discovery has remained unpublished for nearly two years since it was made by the United States Department of Agriculture's Bee Research Laboratory.

Such a finding from the American Government's own bee lab would raise serious questions about the use of neonicotinoid insecticides - compounds which mimic the insect-killing properties of nicotine - and which are increasingly used on crops around the world.

Bayer, the German chemicals giant which developed the insecticides and makes most of them, insists 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 £510 million ($1.07 billion).

The worry is that neonicotinoids, which are neurotoxins - 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 bees and other pollinating insects can absorb them and carry them back to their hives or nests.

The American study, led by Dr Jeffrey Pettis 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 in microscopic doses.

Pettis and his team found that increased disease infection happened even when the levels of the insecticide were so tiny they could not subsequently be detected in the bees, although the researchers knew that they had been dosed with it.

Pettis said his research had 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 at this time."

However, the findings have been revealed because Pettis and a member of his team, Dennis van Engelsdorp, of Penn State University - both leaders in research on colony collapse disorder - 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.

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 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 significantly weakened honey bees."

Neonicotinoids have caused controversy since Bayer introduced them in the 1990s and have been blamed by some beekeepers and environmental campaigners as a potential cause of colony collapse disorder, in which billions of worker bees abruptly disappear from their hives.

It was first observed in the US in 2006.

Neonicotinoids have been banned, to varying degrees, in France, Germany, Italy and Slovenia, although they are freely sold and widely used in the US and Britain.

In Britain, the Co-operative Group has banned them from farms from which it buys vegetables, but the Government has rejected appeals from beekeepers and environmentalists to suspend their use as a precaution.

This week, calls were made in the Commons by the Labour MP for Gower, Martin Paton, calling again for the Government to suspend use of the compounds following controversy in the US over Bayer's latest neonicotinoid, clothianidin.

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 Britain is Buglife, the invertebrate conservation charity, which last year published a review of all the research done on the chemicals' effect on "non-target" insects such as honeybees and other pollinators.

Buglife director Matt Shardlow said of the Pettis study: "This 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 colony collapse disorder and the loss of wild pollinator populations.

"The weight of evidence against neonicotinoids is becoming irresistible - the Government should ... ban the risky uses of these toxins."

Bayer insists its neonicotinoids are safe for bees when used properly. 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.

"I'm sure there are some very interesting effects Dr Pettis has seen in a laboratory, but 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."

Silent hives

* Between 20 and 40 per cent of American hives have been affected by colony collapse disorder, a catastrophic disease wiping out bees around the world.

* Colony collapse disorder has since been seen in other countries from France to Taiwan, though not yet in Britain or New Zealand.

* The chemical giant Bayer insists its insecticide products - linked by some critics to bee mortality - are bee-safe. But French and German beekeepers have blamed them for large bee losses.

- INDEPENDENT