click image to zoomCourtesy Agricultural Research ServiceA larger percentage of managed honeybee colonies survived this winter compared to the previous winter.Honeybee deaths decreased about 7 percent during the 2013-14 winter from the previous winter, according to an annual survey of beekeepers.
The survey, conducted by the U.S. Department of Agriculture and the Bee Informed Partnership, found winter mortality from all causes was 23.2 percent, down from 30.5 percent in 2012-13, according to a news release.
The survey spanned from October 2013 through April 2014 and involved about 7,200 beekeepers who managed about 564,000 colonies.
The eight-year average winter loss is 29.6 percent.
Previous surveys have found winter losses ranging from 21.9 percent in 2011-12 to as high as 36 percent in 2007-08.
"Yearly fluctuations in the rate of losses like these only demonstrate how complicated the whole issue of honeybee heath has become, with factors such as viruses and other pathogens, parasites like varroa mites, problems of nutrition from lack of diversity in pollen sources, and even sublethal effects of pesticides combining to weaken and kill bee colonies," Jeff Pettis, survey co-author and research leader of the Agricultural Research Service Bee Research Laboratory in Beltsville, Md., said in the release.
One of the challenges is there is no way to tell why the bees did better this year than last year.
Among the leading causes of colony losses reported by the beekeepers in past surveys have been queen failure, poor overwintering conditions and varroa mites.
An increasing number of researchers say they believe that varroa mite, a pinhead-sized parasite that litterally sucks the life from bees, is one of the largest contributors to poor colony health.
Despite the decrease in winter mortality this season, it still remains above a roughly 19 percent level that beekeepers consider economically sustainable.
This year, nearly two-thirds of beekeepers responding to the survey pegged their losses as greater than the economic threshold.
The complete results of the survey will be available later this year, but you can view an abstract at Bee Informed.
The Bee Informed Partnership comprises university and USDA experts as well as leaders from the honeybee industry. Its goal is to develop practical methods that the industry can adopt to reduce honeybee mortality.