Report links Varroa mite, variety of factors to bee losses
By JOHN O'CONNELL
A new report analyzing rising losses of bee colonies outlines a host of explanations, emphasizing the parasitic Varroa mite as the major factor.
According to the report, released May 2 by USDA and the U.S. Environmental Protection Agency, mites have developed widespread resistance to the chemicals beekeepers use to control them within hives, and several new viruses have emerged in U.S. bees.
Since 2006, an estimated 10 million beehives have been lost, with a $2 billion replacement cost to beekeepers. Idaho beekeepers say losses last winter were especially acute.
"Consensus is building that a complex set of stressors contribute to pollinator declines, and researchers are increasingly studying multiple factors of colony losses," the report reads.
The Varroa mite, first found in the U.S. in 1987, is to blame for increasing levels of many bee viruses, according to USDA.
"It seems to me the most significant thing beekeepers can do is keep Varroa mites down," said Roger Porter, a Chubbuck, Idaho, beekeeper. "Varroa mite is the scourge."
Porter, who loses 10 percent of bees in a normal winter, lost half of his colonies this winter, with most in December. Porter believes more research is needed on bee miticides and how they affect colony health. For the past two years, he's used a nontoxic hop-derived miticide called Hopguard, with good results when applied at temperatures above 60 degrees.
Scot Bischoff, a Downey, Idaho, beekeeper with 4,000 hives, lost a quarter of his hives this winter, about double the normal rate. Nationally, he believes some beekeepers cut back on miticides due to sharp price increases. In Idaho, he suspects the stress last season of a cold spring limiting the bloom and a dry summer stressed and weakened bees. The tough weather conditions forced Bischoff to feed his bees more than normal to minimize losses.
Bischoff also believes agricultural pesticides and chemical spraying of roadsides have impaired bees.
Reed Findlay, a University of Idaho Extension educator from Power County who keeps bees, theorizes beekeepers suffered a "double-whammy" last season because they got lackadaisical on mite control and had a cold spring and dry summer. Findlay and Porter agree that there's too little unbiased scientific data to link colony collapse to pesticides.
"A lot of the main people studying bees are shying away from the pesticide link and looking more at drought, mites and new diseases," Findlay said.
The federal report calls for breeding of bees to increase genetic diversity to limit diseases. The report also highlights how poor nutrition may be making bees more susceptible to disease and parasites, and broadening the variety of forage for bees could improve colony health.
The report concludes the role pesticides may play in colony collapse is unclear and should be further studied. It also suggests increasing outreach to farmers to help manage bees' exposure to pesticides and implementing better monitoring of beekills.
The report outlines the proceedings of an October 2012 conference in Alexandria, Va. The conference was organized by the Colony Collapse Disorder Steering Committee, formed in early 2007 and led by USDA and EPA, partnering with Pennsylvania State University to bring stakeholders together to study the issue.