Fewer honeybees died this past winter than in previous ones, although bees are still dying at a rate that is not economically sustainable, according to a federal report published Thursday.
The new survey, issued by the U.S Department of Agriculture and the Bee Informed Partnership, found that nationwide losses of managed honeybee populations from all causes was down to 23.2%, a drop of nearly 7% from the winter before when death rates were at 30.5%.
Over the past eight years, beekeepers have reported average winter losses of 29.6%.
That’s still no reason to celebrate. Beekeepers say they lose money every year that losses exceed 18.9%, according to the USDA.
Honeybee die-offs have been blamed on a combination of factors, including pesticides, disease, parasites, poor nutrition, bad weather, and the stress of being trucked from orchard to orchard to pollinate different crops. Colony collapse disorder, a mysterious phenomenon in which bees vanish from their hives, may be triggered by one or a number of these pressures.
“Yearly fluctuations in the rate of losses like these only demonstrate how complicated the whole issue of honey bee heath has become,” Jeff Pettis, coauthor of the survey and leader of the government’s bee research laboratory in Maryland, said in a statement.
The report comes after a Harvard study that found a strong link between the most widely used class of pesticides — neonicotinoids — and colony collapse disorder. Some scientists have dismissed the report, taking issue with the small sample size (only 18 colonies were tested) and noting the pesticides used to treat the colonies were not administered to the bees in a way that would be found in nature.
Rather than targeting pesticides, the government report said there is a “growing consensus among researchers that one of the largest contributors to poor colony health and colony losses is the varroa mite.”
The mite is an Asian-bee parasite that first arrived in U.S. in 1987.
“What is clear from all of our efforts is that varroa is a persistent and often unexpected problem,” Dennis van Engelsdorp, director of the Bee Informed Partnership and an entomologist at the University of Maryland. “Every beekeeper needs to have an aggressive varroa management plan in place. Without one, they should not be surprised if they suffer large losses every other year or so.”
Monsanto, Bayer, and other pesticide companies also “say the bees are being killed by other factors, such as mites,” Reuters said.
According to the website, Monsanto, a maker of pesticides, owns one of the companies that collaborated with the USDA on the report.
The survey results are based on self-reported information from 7,200 beekeepers, who represent 21.7% of the country’s 2.6 million colonies.
NOW WATCH: Briefing videos
Business Insider Emails & Alerts
Site highlights each day to your inbox.