USDA study identifies pesticide resistance in mites tied to bee colony die-offs
July 14, 2025
By Ryan McGeeney
U of A System Division of Agriculture
Fast Facts:
- Varroa mites are common pest, disease vector in bee colonies
- Amitraz has long been used to control mites
- Bee experts recommend rotating modes of action, non-chemical approaches
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(Newsrooms: Download photo of a varroa mite)
FAYETTEVILLE, Ark. — A long-favored mode of action for controlling mites in honey bees appears to be reaching the limits of its effectiveness, according to a report from U.S. Department of Agriculture researchers published in June.
Although the phenomenon of “colony collapse disorder” has been known and studied in the United States and elsewhere for decades, researchers noted that the degree of die-off recorded this spring among large commercial beekeeping operations averaged more than 60 percent across the country.
A common thread in nearly all of the failed colonies was the presence of varroa mites, a pest known to be a frequent disease vector for bees. Jon Zawislak, extension entomologist for the University of Arkansas System Division of Agriculture, said the mites were found to have developed a resistance to the miticide amitraz, which both commercial and hobbyist beekeepers have used to control the mites in beehives for many years.
“Amitraz is probably the most widely used product among commercial beekeepers,” Zawislak said. “They’ve been using it for so long that resistance has built up. It’s actually surprising that it took this long to happen. A number of other products that were being used, the mites became resistant in just a couple of years.”
While both chemical modes of action and organic medicines are available to control the mites, the organic options tend to be more labor-intensive.
“There’s a whole range of medications and products that a beekeeper can employ,” he said. “But those requiring the least amount of time and effort are on the chemical end of the spectrum. So for a backyard beekeeper who has two or three colonies, you can manage those with a little more effort, but when you’re managing 70,000 or 80,000 colonies, just the cost of material to put in the hive once or twice a year adds up, and so does the labor involved — having to open every one of those colonies, put some medication in, then come back and take it back out.”
The USDA study drew samples from six large commercial producers, none of which were in Arkansas. But beekeepers in the Natural State are no strangers to the challenges of keeping colonies healthy.
Steve Culp, a former Craighead County extension agent and owner of Culps’ Honey Farm, maintains about 3,500 honeybee colonies in northeast Arkansas. He said managing die-off is just part of the business.
“For the last 10-12 years, we have typically lost 40-50 percent of our colonies in a calendar year period,” Culp said. “We’ve always had a certain amount of that, but I’d say 15 to 18 years ago, it was half what we’re losing now.
“If it was a cattle operation, it’d be a disaster,” he said. “But we can make a lot more bees, within reason. We’ve got to make 60 percent of the bees we have each year just to stay even.”
Zawislak said that although Amitraz-resistant varroa mites are certainly a factor in growing die-offs, they are only part of a spectrum of challenges affecting bee populations, including the conversion of wild habitat to agricultural and urban development, the increasing prevalence of self-pollinating crops and the widespread use of chemical agricultural inputs.
“All these sources of stress are interconnected,” he said. “They all have negative effects on bee vitality, productivity and longevity. Anything that weakens an individual bee makes it more susceptible to pathogens and potentially shortens its lifespan.
“Individual worker bees have very short lifespans anyway, just a matter of a few weeks,” Zawislak said. “But in a healthy colony, they’re constantly replaced. But if their lives are shortened by just a few days, there’s a cumulative effect on the whole colony, and it will start to dwindle and fail because they’re dying faster than they can be replaced.”
James Rhein, president of the Arkansas Beekeeping Association, said that among the several beekeeping organizations of which he is a member — including clubs in Mississippi and Missouri — most members maintain between five and 10 hives, and reported losing between one and three colonies over the past year. He said he credits his own success — losing zero colonies out of about 35 over the past year — to the use of non-miticide methods of controlling pests in his hives.
“There’s nothing on the horizon that’s going to kill all our mites,” Rhein said. “You’re trying to kill a bug on a bug. There are things you can use, however, that don’t kill the mites but will knock them back to a level that the bees can tolerate. I use screen bottoms, brood-breaks and mite-resistant queens from Russia. None of these things will kill the mites, but altogether, they knock the mites back a level so the bees don’t have a problem.”
Zawislak, who teaches a three-part introductory series for Arkansans interested in becoming beekeepers each year, said he has long encouraged producers to practice alternating modes of action to control pests while avoiding resistance development.
“Different products will attack the pests on different parts of their biology,” he said. “So if you’re using the same class of chemicals year after year, that speeds up resistance. But if you rotate ‘product A’ with ‘product B’ on an annual basis, the mites that might be building up a resistance to one will get shocked by the other.
“We do have other options available, though none of them are 100 percent effective against these mites,” Zawislak said. “There’s no silver bullet. There’s some new products in the pipeline, but they haven’t cleared all the regulatory hurdles yet.”
To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit www.uaex.uada.edu. Follow us on X and Instagram at @AR_Extension. To learn more about Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website: https://aaes.uada.edu/. Follow on X at @ArkAgResearch. To learn more about the Division of Agriculture, visit https://uada.edu/. Follow us on X at @AgInArk.
About the Division of Agriculture
The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land grant education system.
The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on three campuses.
Pursuant to 7 CFR § 15.3, the University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.
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Media Contact:
Ryan McGeeney
rmcgeeney@uada.edu
501-671-2120