Beekeepers lost three of every 10 of their managed honeybee colonies to harsh weather this past winter, the highest winter mortality rate in five years. The losses propelled the annual loss rate to 40 percent for the year ended on March 31, according to a nationwide survey released on Wednesday. The not-for-profit Bee Informed Partnership said its survey also found that beekeepers are increasing the level of losses they consider acceptable.
Annual colony losses have reached or exceeded 40 percent in four of the past six years. The peak for annual losses was 45 percent in 2012/13. Bee Informed, a partnership of research labs and universities, began surveying winter losses in 2006/07 and expanded the survey to include annual losses in 2010/11. Reports of dramatic declines in bee populations were the impetus for the survey of bee health. Pests, disease, nutrition, and insecticides are considered factors in the declines.
Winter is the hardest season for honeybees because the food supply is limited and the production of new bees slows or stops, said Auburn University assistant professor Geoffrey Williams, the coordinator of the latest survey. The winter mortality rate of 30.7 percent in 2017/18 is the highest in eight years; the 10-year average is 27.9 percent. Summer-season losses of 17.1 percent for 2017/18 were on par with the 10-year average of 18.2 percent, according to Bee Informed.
Beekeepers taking part in the survey, on average, said they considered the acceptable winter loss rate to be 20.6 percent, up from 18.7 percent in the previous year and the highest percentage recorded since the survey began.
“We don’t have a solid explanation of why that acceptable rate continues to climb, but it could be that beekeepers are being realistic about potentially higher losses,” said Williams. “For them, it could be the new norm.”
The varroa mite, a parasite, is the No. 1 “health stressor,” and affected 41 percent of bee operations last spring, according to the USDA’s annual Honey Bee Colonies report. “Other pests and parasites” infested nearly 12 percent of colonies, pesticides affected 13 percent of colonies, and disease was reported in 4 percent. The USDA said losses from colony collapse disorder in early 2017 were down significantly from the first quarter of 2016.