Discuss as:

Pesticides aren't the biggest factor in honeybee die-off, EPA and USDA say

From 2012: Honeybees may be victims of widely used insecticides. NBC's Anne Thompson reports.

The U.S. government's latest report on the mysterious disappearance of honeybees points to a parasitic mite as the biggest factor behind colony collapse disorder — and downplays the role of controversial pesticides that European officials are planning to ban.

Thursday's report from the Environmental Protection Agency and the U.S. Department of Agriculture says there should be further research into the effects of those nerve-agent pesticides, known as neonicotinoids. But it says the studies so far have not shown it to be the biggest hazard facing the bees.

Last month, beekeepers and environmentalists filed a federal lawsuit calling for an immediate ban on two kinds of neonicotinoids — clothianidin and thiamethoxam. One of the attorneys bringing that suit, Peter Jenkins of the Washington-based Center for Food Safety, told NBC News that his group was "very disturbed" by the way the report was presented, but he also said some of the problems cited in the report supported his case.

'Complex problem'
The report says that a complex combination of causes is behind colony collapse disorder, or CCD, a term that applies to the difficult-to-explain losses that have hit U.S. honeybee colonies since 2006. In the worst cases, entire colonies have disappeared within a few weeks. That's a big problem, because the government says an estimated one-third of all food and beverages are made possible by pollination, mainly by honeybees. Pollination is said to be worth more than $20 billion in agricultural production annually.

The relatively light bee colony losses during the winter of 2011-2012 gave some experts reason to hope that the CCD situation was getting better, but experts say that last winter's losses look as if they were worse than ever.

"The decline in honeybee health is a complex problem caused by a combination of stressors, and at EPA we are committed to continuing our work with USDA, researchers, beekeepers, growers and the public to address this challenge," acting EPA Administrator Bob Perciasepe said in a statement.

Deputy Agriculture Secretary Kathleen Merrigan promised that "key stakeholders will be engaged in addressing this challenge."

Scott Bauer / USDA via AP

A worker bee carries a Varroa mite, visible in this close-up view.

The report draws upon a gathering of officials and stakeholders that took place in Alexandria, Va., last October. It says that the parasitic Varroa mite is the "major factor" behind CCD in the United States and other countries. Varroa mites latch onto the bees and feed on their fluids, weakening the insects. The mites have developed widespread resistance to the chemicals that have been used to control them. The report says more attention should be given to breeding bees that can weather the mites, and notes that gene-sequencing projects focusing on honeybees as well as Varroa mites may provide fresh insights.

Beekeepers have long known about the mite problem, as well as the other causes listed in the EPA-USDA report: poor nutrition, reduced genetic diversity, the Nosema gut parasite, emerging viruses and a bacterial disease called European foulbrood. But figuring out the role played by pesticides has posed the biggest challenge for researchers as well as policymakers.

What to do?
Recent research studies have focused on the effect of neonicotinoids, a neurotoxic type of pesticide that has become widely used because they have little effect on mammals. Most of the studies suggest that the pesticides can scramble a bee's brains — but at what level of exposure?

Some say the exposure levels used in those studies may not accurately reflect the levels that bees experience in the fields. That's the tack taken in Thursday's report: "The most pressing pesticide research questions lie in determining the actual field-relevant pesticide exposure bees receive, and the effects of pervasive exposure to multiple pesticides on bee health and productivity of whole honeybee colonies," it said.

The report says residues from a different class of pesticides, known as pyrethroids, could pose three times as much risk to bees as neonicotinoids.  

The Center for Food Safety's Peter Jenkins complained that the effects of neonicotinoids were being downplayed, but he also called attention to some of the shortcomings mentioned in the federal agencies' report. "They admitted that their labeling is inadequate," Jenkins said. "They admitted that past risk assessments and data requirements were inadequate."

He said some of the proposed policy changes — including, for instance, the introduction of better equipment for coating seed corn with pesticides — would have a positive impact. "What they don't say is that it's going to take years and years to achieve those changes," Jenkins said.

Jenkins called for an immediate tightening of regulations of pesticides. "The one factor that EPA actually has control over is the one that they refuse to regulate," he said.

The EPA is working on a new round of risk assessments for pesticides, but the results of those assessments have not yet been released. Meanwhile, the agency is due to file its response to the environmentalists' lawsuit later this month. Jenkins said Thursday's report would have "no real effect" on the legal action, which could go on for years.

More about the bee die-off:

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.