The survey consisted of 6,128 beekeepers, who represent 14.5 percent of the nation's 2.74 million managed honeybee colonies, says the Bee Informed Partnership. Of those surveyed, 67.2 percent "experienced winter colony loss rates greater than the average self-reported acceptable winter mortality rate of 18.7 percent."
The number of bees lost during the winter of 2014-15 was actually lower than in the winter of 2013-14, but an increase of summer losses led to higher overall losses, the survey said. Beekeepers lost 27.4 percent of colonies in the summer of 2014, compared to 19.8 percent in 2013.
"Nobody knows with certainty why. Beekeepers once expected to lose perhaps 10 percent of their bees in an average year," Wines writes. "But deaths began to spike in the middle of the past decade, when a phenomenon in which bees deserted their hives and died en masse—later named colony collapse disorder—began sweeping hives worldwide." Losses also have been partly blamed on pesticides. (Bee Informed graphic)