Skip to content

U.S. Beekeepers Lost 23% of Colonies Last Winter; Scientists Recommend Treating Bees for Varroa Mites

According to a national survey of honey bee colony losses conducted by the Bee Informed Partnership, the Apiary Inspectors of America, and the U.S. Department of Agriculture, U.S. beekeepers lost more than one in five honey bee colonies in the winter of 2013-2014 — significantly fewer than the winter before. But tough times continue for commercial beekeepers, who are reporting substantial honey bee losses in summer as well. Beekeepers who tracked the health of their hives year-round reported year-to-year losses of more than one in three colonies between spring 2013 and spring 2014.

University of Maryland entomologist Dennis vanEngelsdorp, who directs the Bee Informed Partnership, led a team of 11 researchers who conducted the survey. A total of 7,183 beekeepers, who collectively manage about 22 percent of the country’s 2.6 million commercial honey bee colonies, took part.

No single culprit is responsible for all of the honey bee deaths, but their research shows mortality is much lower among beekeepers who carefully treat their hives to control a lethal parasite called the Varroa mite.

“If there is one thing beekeepers can do to help with this problem, it is to treat their bees for Varroa mites,” said vanEngelsdorp. “If all beekeepers were to aggressively control mites, we would have many fewer losses.”

The beekeepers were asked to list the probable causes of their losses, and in a separate survey some of them also described how they managed their hives. Those responses are still being analyzed, but an initial review, previous fieldwork, and past surveys all point to Varroa mites as a persistent and controllable problem.

“Every beekeeper needs to have an aggressive Varroa management plan in place,” vanEngelsdorp said. “Unfortunately, many small-scale beekeepers are not treating their bees, and are losing many colonies. And those colonies are potential sources of infection for other hives.”

Blue bars show the percentage of winter honey bee colony losses considered “acceptable” by U.S. commercial beekeepers participating in the annual national survey. Red bars show the percentage of colonies actually lost each winter by the participating beekeepers. Credit: Bee Informed Partnership.

The survey found that 23 percent of the managed honey bee colonies in the U.S. died between Oct. 1, 2013 and March 31, 2014. That’s well below the average loss of 29 percent over the survey’s history.

However, summer death rates were nearly as high as the winter ones. Over the summer, about 20 percent of survey respondents’ colonies died. Losses between spring 2013 and spring 2014 averaged 34 percent. (The winter and summer losses do not match up to the year-to-year losses because not all beekeepers filled out all sections of the survey.)

“Rising and falling rates of colony losses demonstrate how complicated the issue of honey bee health has become,” said Jeff Pettis, a survey co-author and research leader of the USDA’s Bee Research Laboratory in Beltsville, MD. Pettis pointed out that the causes of honey bee colony failures are complex, including Varroa mites, other parasites and viruses; poor nutrition, which can be due to a shortage of wildflowers in herbicide-sprayed or drought-stricken farm fields; and exposure to insecticides and fungicides.

Now in its eighth year, the survey originally focused on winter mortality in managed honey bee colonies. The generation of bees that lives through the winter must survive months longer than summer bees’ 30-day lifespan. In winter, honey bees don’t produce offspring and are confined in a hive where diseases can spread.

“We used to think winter was the critical period,” vanEngelsdorp said. “But during our field studies, beekeepers told us they were also losing colonies in the summer months. So we expanded the survey and found that in fact, colonies are dying all year round.”

About two-thirds of beekeepers surveyed, who ranged from hobbyists to large businesses, said their colonies suffered unacceptable losses –greater than the 19 percent mortality rate that, on average, they were willing to absorb. It was the second year in a row that most beekeepers reported unacceptably high mortality.

A summary of the 2013-2014 survey results is available at


  1. The recent report, “National Honey Bee Loss Declines,” has many caveats which are not featured in media articles. The Bee Informed Partnership compiling the report states “This is a preliminary analysis.” The data they collect is provided voluntarily by beekeepers across the U.S. It is key to note this report reflects only 21.7% of the total 2.6 million colonies in the nation. This report reflects less than a quarter of the total managed bee colonies in the country. The beekeeping industry is comprised of backyard, side-liner, and commercial beekeepers with each category defined by the number of bee hives. If a majority of beekeepers reporting are backyard beekeepers with 1-10 hives that experience only an urban and suburban environment, their losses will be different compared to sideline and commercial beekeepers who travel around the state or the country pollinating crops, and exposing their bees to rural, and distinctly agricultural areas. The survey relies on beekeepers to voluntarily submit their information, and this report reflects less than a quarter of the total hives in the U.S.. The authors of the report
    reiterate these are “preliminary results.” As all research, the full report will give us greater information in order to make an informed conclusion. Talking with beekeepers across the country, losses over the winter were high for beekeepers in the winter states, as the winter was much longer this year. In the southern states where many commercial bees reside beekeepers reported losses exacerbated by pathogens and pre-lethal pesticide exposure weakening bees. One beekeeper reported 60% losses in his commercial operation. Before claiming less national losses, the complete story will be revealed in the full report.

    M. Colopy, Program Director
    Pollinator Stewardship Council

  2. Hi, just start here in Brazil a treatment injection ozone at a live beehive and getting good results. So far we are able to inject ozone for 20 minute at the entrance at a beehive, placing a white paper with some liquid vasile and getting counts fo some varroa mites dropping dead. We start this a few days ago and need some advice to improve my research.
    Is there anyone that can help me with this test?
    Here in Brazil we don´t have much problems with Varroa but I know that is a big problem in USA.
    Thanks in advance.

    Mauro Massari

    • Hi Mauro,

      how much ozone do you put into the beehive? Or what device do you use? How much O3 /hour does it produce?


      Vladimir Domen Slovakia (Europe)

  3. Ozone is easy to get and would appear to be less damaging to the honey and the bees. Not sure how it will work in stopping the varroa mite?

    • Good news for all from Italy!

      We have concluded our trials using ozone on bees.
      The results is very intersting.
      Applying 20 minutes of ozone in the hives, when all the bees are inside, we received as result the dead of all varroa inside the colonies for a long period, more than 21 days. All the stadium of varroas fall down dead after few hours.
      We founded the colonies without varroa, EFB, AFB, Nosema sp. ect.
      We used a tool with five erogators at same time, to semplify the work in the apiaries.

Leave a Reply (Comments subject to review by site moderator and will not publish until approved.)

This site uses Akismet to reduce spam. Learn how your comment data is processed.