WASHINGTON — The devastation of American honeybee colonies is the result of a complex stew of factors, including pesticides, parasites, poor nutrition and a lack of genetic diversity, according to a comprehensive federal study published Thursday.
The problems affect pollination of U.S. agricultural products worth tens of billions of dollars a year. The report does not place more weight on one factor over another, and it recommends a range of actions and further research.
Since 2006, millions of bees have been dying in a phenomenon known as colony collapse disorder. The causes have been the subject of much study and speculation.
The federal report, issued Thursday by the Department of Agriculture and the Environmental Protection Agency, said the biggest culprit is the parasitic mite varroa destructor, calling it “the single most detrimental pest of honeybees.”
The problem has also hit bee colonies in Europe, where regulators are considering a ban on a type of pesticides known as neonicotinoids. The U.S. report cites pesticides, but near the bottom of the list of factors. Federal officials and researchers advising them said the science doesn’t justify a ban of the pesticides yet.
At a news conference Thursday, Sonny Ramaswamy, a top USDA official, said the scientific consensus is that there are multiple factors “and you can’t parse any one out to be the smoking gun.”