Pesticides still suspect in US bee colony disorder - USDA

25 August 2009 00:04  [Source: ICIS news]

WASHINGTON (ICIS news)--US government researchers said on Monday that pesticides remain a potential cause or contributing factor in the ongoing and mysterious collapse of bee colonies nationwide.

However, new research suggests that a virus may be responsible for the apparent epidemic that for three years has plagued the 2.3m bee colonies that are maintained in the US for agricultural pollination needs.

Known as colony collapse disorder (CCD), the epidemic is characterized by a sudden disappearance of a colony’s bees with few, if any, dead bees left behind.  For some unknown reason, a colony’s bees will fly off and never return.

Although the disorder may have been building for several years, it first came to crisis-level attention after the 2006-2007 North American winter season, when 32% of the nation’s cultivated bee colonies disappeared.

The disorder accelerated following the 2007-2008 winter season, when 36% of colonies were found to have collapsed. Bee losses were less severe following the 2008-2009 winter, reported by the US Department of Agriculture (USDA) at 29%.

However, even that reduced rate of colony collapse puts a major part of US agriculture at risk, according to the department.

“While the drop in losses is encouraging, losses of this magnitude [29%] are economically unsustainable for commercial beekeeping,” said Jeff Pettis, CCD research leader at the department’s Agricultural Research Service (ARS).

Continuing yearly losses of 30% for managed bee colonies nationwide poses a serious risk to about $15bn (€10.5bn) worth of annual US agricultural crops that depend chiefly on bees for pollination.

ARS officials noted that about one-third of the US diet - including most fruits, vegetables and vine crops - depend on bee pollination. Major food staple crops, such as corn, wheat and rice, are wind pollinated and have not been affected by the disorder.

Research results announced on Monday indicate that bees in colonies afflicted with the disorder have a higher overall level of viruses and other pathogens than normal colonies.

The new study also indicated that bees in CCD colonies “did not show significantly active pesticide response genes”.

“But we can’t go so far as to say that pesticides are exonerated,” said ARS spokesperson Kim Kaplan. “We still don’t know what is causal and what is result. There is a greater suspicion of a viral cause, but ‘suspicion’ is about as far as anyone is willing to go right now.”

“We still believe it will be multiple factors, perhaps including pesticides,” she added.

Kaplan said the disorder could be the result of a combination of pesticide exposure, viral infections and environmental stresses, such as drought or nutrition changes.

“Pesticides remain one of the potential factors,” she said.  “At this point, we have not found the cause, and we’re still looking at links and correlations and associations.”

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By: Joe Kamalick
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