Beekeepers in the U.S. lost nearly half of their honey bee colonies between April 2015 and April 2016, according to the preliminary results of a survey.
In a blog post earlier this week, the Bee Informed Partnership said that rates of loss in both winter and summer had worsened compared to the year before. Beekeepers lost 44 percent of their colonies, it said.
"We're now in the second year of high rates of summer loss, which is cause for serious concern," Dennis vanEngelsdorp, project director for the Bee Informed Partnership, said in a statement.
"Some winter losses are normal and expected. But the fact that beekeepers are losing bees in the summer, when bees should be at their healthiest, is quite alarming," vanEngelsdorp added.
The survey was conducted by the Bee Informed Partnership in collaboration with the Apiary Inspectors of America and with funding from the U.S. Department of Agriculture (USDA).
The Bee Informed Partnership said that the presence of the varroa mite was one contributor to the losses, with pesticides and malnutrition "also likely taking a toll."
The USDA describes honey bees as being a "critical link in U.S. agricultural production" and says that pollination by managed honey bee colonies contributes "at least $15 billion to the value" of U.S. agriculture every year.
"The high rate of loss over the entire year means that beekeepers are working overtime to constantly replace their losses," Jeffery Pettis, a senior entomologist at the USDA and a co-coordinator of the survey, said in a statement on the Bee Informed Partnership website.
"These losses cost the beekeeper time and money," Pettis added. "More importantly, the industry needs these bees to meet the growing demand for pollination services. We urgently need solutions to slow the rate of both winter and summer colony losses."