ST. PAUL -- An annual survey of beekeepers shows honey bees continue to die at high rates. Between April 2020 and this April, losses across the country averaged 45.5 percent according to preliminary data from the Bee Informed Partnership, a collaboration of researchers that has conducted the annual bee loss survey for 15 years.

Bee mortality reported by 3,347 beekeepers, representing about 7% of all honey bee colonies across the country, was the second-highest since the survey began in 2006.

Researchers say the high losses were in part because more bees die throughout the year.

"Earlier on in this activity we kind of felt like people lost most of their bees in the winter, but particularly this year and last year, these kind of loss events are occurring year around," said Mikayla Wilson at the University of Maryland.

Those high losses don't mean managed honey bees are disappearing, the overall number of bee colonies is relatively stable, but it means beekeepers need to spend more time and money dividing their surviving bee colonies to create new ones that replace those lost.

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"The total number of bees in the United States, we feel like that is relatively balanced, but that activity of having to divide colonies is a great amount of pressure on the beekeepers and a tremendous amount of labor," said Wilson.

The queen bee (darker and longer, in center of photo) in a the hive of a Grant, Minnesota, beekeeper in 2014. St. Paul Pioneer Press file photo
The queen bee (darker and longer, in center of photo) in a the hive of a Grant, Minnesota, beekeeper in 2014. St. Paul Pioneer Press file photo

Because most commercial bee operations travel from state to state for crop pollination, losses they report are calculated in all states they worked in, making it more difficult to calculate state by state bee mortality.

The latest survey shows Minnesota bee losses for last winter were 31.6%, about the same as the national average.

Commercial honey bee operations pollinate an estimated $15 billion worth of food crops each year.

“Though we see fluctuations from year to year, the worrisome part is we see no progression towards a reduction of losses,” said Nathalie Steinhauer, the partnership’s science coordinator.

“We see in the survey signs that beekeepers are adjusting their practices over time,” said Steinhauer. “We also see that their perception of risk is changing. The level of acceptable loss, which was originally around 15% in earlier years of the survey, has crept up to 23% this year.”

The survey found parasitic varroa mites and problems with queen bees were the primary reasons colonies were lost.

There has been some progress in understanding the reasons for the high loss of managed honey bees, including improved methods of treating bees for the parasitic varroa mite, cited as one of the most common causes a bee colony is lost. Efforts to increase plants on the landscape that provide essential nutrition for bees, and to reduce the use of pesticides known to harm bees, are underway.

“But there are still a lot of issues that are left unaddressed,” said Steinhauer. “It seems we’re running to stand still because beekeepers are changing their practices, and yet we still don’t see a clear improvement in their loss rates.”