The mysterious die-off of the nation’s honeybees worsened last year, with a spike in summer deaths indicating a troubling new development.
Each year the Bee Informed Partnership in collaboration with the Apiary Inspectors of America conducts a survey among both commercial and backyard beekeepers to track the health and survival rates of their honeybee colonies. What the results reveal for April 2014 to April 2015 are dismal. Beekeepers surveyed lost a total of 42.1 percent of their colonies during the period. And while winter loss rates dipped .6 percent (from 23.7 percent last year to 23.1 percent this year), summer loss rates increased significantly, from 19.8 percent to 27.4 percent, which is troubling. The health of bee colonies isn't getting better.
"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 etymologist from the University of Maryland and project director for the Bee Informed Partnership. “We expect the colonies to die during the winter, because that’s a stressful season. What’s totally shocking to me is that the losses in summer, which should be paradise for bees, exceeded the winter losses.”
"Years ago, this was unheard of," he added.
The losses among small-scale beekeepers (those with fewer than 50 colonies) seems clearly related to the varroa mite, a pesky and deadly parasite that is contagious between colonies; but for commercial beekeepers, the reason behind the losses remain less clear.
"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 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,” said Jeffery Pettis, a senior entomologist at U.S. Department of Agriculture and a co-coordinator of the survey. “But such high colony losses in the summer and year-round remain very troubling,"