Beekeepers in the United States lost a concerning 40 percent of their honey bee colonies between April 2014 and April 2015.
Winter loss rates slightly improved from previous years, but not enough to counter the severe overall losses observed in a nationwide study, the University of Maryland reported. Summer losses were particularly high, and researchers are concerned bee colony health is on a dangerous downward trend.
"We traditionally thought of winter losses as a more important indicator of health, because surviving the cold winter months is a crucial test for any bee colony," said Dennis vanEngelsdorp, an assistant professor of entomology at the University of Maryland and project director for the Bee Informed Partnership. "But we now know that summer loss rates are significant too. This is especially so for commercial beekeepers, who are now losing more colonies in the summertime compared to the winter. Years ago, this was unheard of."
Beekeepers who responded to the survey reported an annual loss of 42.1 percent. Winter loss rates were reported to have dropped from last year's 23.7 percent to 23.1 percent, but summer loss jumped from 19.8 percent to 27.4 percent. Beekeepers who manage fewer than 50 colonies, or "backyard beekeepers," believe the increase in loss can be blamed on the varroa mite, which is a lethal parasite that can be spread among colonies; for commercial beekeepers, the cause of the loss is murkier.
"Backyard beekeepers were more prone to heavy mite infestations, but we believe that is because a majority of them are not taking appropriate steps to control mites," vanEngelsdorp said. "Commercial keepers were particularly prone to summer losses. But they typically take more aggressive action against varroa mites, so there must be other factors at play."
The loss survey encompassed over 6,000 beekeepers from all 50 states. The beekeepers included in the study manage about 15 percent of the U.S.'s 2.74 million domestic bee colonies. The total economic value of honey bee pollination services are estimated to range between $10 billion and $15 billion annually.
"The winter loss numbers are more hopeful especially combined with the fact that we have not seen much sign of Colony Collapse Disorder (CCD) for several years, but such high colony losses in the summer and year-round remain very troubling," said Jeffery Pettis, a senior entomologist at U.S. Department of Agriculture and a co-coordinator of the survey. "If beekeepers are going to meet the growing demand for pollination services, researchers need to find better answers to the host of stresses that lead to both winter and summer colony losses."
The study is conducted each year by the Bee Informed Partnership in collaboration with the Apiary Inspectors of America.
