More than half of the managed honeybee colonies in Minnesota were lost in the last year, an annual study into nationwide bee deaths estimates.
Preliminary results from the Bee Informed Partnership's colony loss survey for 2014-15 found that beekeepers reported they lost 51.2 percent of colonies in the state in 12 months.
This is more than the national average of 42.1 percent – the second-highest rate of losses recorded in the nine years of the survey. This was driven by a huge increase in losses over the summer (between April and October), with losses during that time hitting 27.4 percent compared to 19.8 percent in 2013.
The rise in summer bee deaths is a cause of concern for University of Maryland researcher Dennis vanEngelsdorp, who led the survey and said these losses are likely to have been caused by poor nutrition and exposure to pesticides.
"It's worrying that we've got this new norm," he told MPR, "where just a continuous sort of hemorrhaging of losses seems to happen all year round."
"These bees are under incredible amounts of stress and we have to figure out what the drivers of those stresses are."
The study found that large, commercial operations lost more colonies during the summer, while smaller enterprises tended to suffer losses during the winter.
MPR notes that a "clear culprit" in the losses on small bee colonies was the varroa mite, a lethal parasite that spreads between colonies, but adds that the major cause of losses at larger operations is not clear.
Bee Informed compiled its results through a survey of 6,128 beekeepers across the country, who manage a combined 398,247 colonies between them.
Insecticide concern prompted MN review
Concern over the collapse of the bee population, and the potentially devastating effect it could have on the U.S. food system, prompted Minnesota's Department of Agriculture to launch a review of the insecticides being used on Minnesota farms in October.
One of the contentious issues that will be addressed is the use of neonicotinoids, one of the most popular insecticides used in agriculture, which some studies suggest could be linked to the widespread death of bees.
NPR News notes neonicotinoids are used to coat the seeds of many agricultural crops including Minnesota's biggest cash crop, corn, to repel insect pests.
The Star Tribune reports Minnesota's Department of Agriculture received more than 400 comments from members of the public calling for officials to include the possibility of banning neonicotinoids in its in-depth study.