Researchers Develop New Varroa Mite Treatment for Beekeepers

Combining amitraz with an inhibiting compound increases the pesticide's effectiveness against resistant mites.

Published on Feb. 26, 2026

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Researchers from the USDA's Agricultural Research Service (ARS) and the University of California, Davis, have discovered a promising new approach to help beekeepers protect their honeybee colonies from destructive varroa mites. The researchers found that combining the widely used mite-killing pesticide amitraz with an inhibiting compound increases the pesticide's toxicity and effectiveness, even against amitraz-resistant mites.

Why it matters

Varroa mites are a major threat to honeybee colonies across the U.S., causing significant harm to bees and spreading deadly viruses that have led to major colony losses. Beekeepers rely on limited pesticide options like amitraz to control mite populations, but the mites are becoming increasingly resistant. This new research offers a potential solution to make existing treatments more effective and help beekeepers better protect their hives.

The details

In the study, researchers placed varroa mites on a petri dish lined with wax foundation and applied treatments using a microinjector. They found that combining amitraz with an inhibiting compound that prevents mites from tolerating the pesticide increased amitraz's killing power by 50% against even amitraz-resistant mites. This approach could provide beekeepers with a practical tool to more effectively control varroa mites and reduce the need for additional treatments, which in turn lowers the selection pressure on mite populations and decreases the economic burden on beekeepers.

  • The study was published on February 16, 2026 in the Journal of Apicultural Research.

The players

USDA's Agricultural Research Service (ARS)

The USDA's agricultural research agency that conducts research to develop solutions for agricultural challenges.

University of California, Davis

A public research university located in Davis, California that collaborates with the USDA on agricultural research.

Julia Fine

A research entomologist at the USDA's Pollinator Health Research Laboratory in Davis, California and a co-leading author of the study.

Sascha Nicklisch

An assistant professor in the UC Davis Environmental Toxicology department and a co-leading author of the study.

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What they’re saying

“This compound inhibits a naturally occurring process that prevents certain chemicals, like pesticides, from accumulating inside cells. If a chemical toxicant can't reach a high enough concentration in a cell, it won't have a toxic effect in the organism. Previously, we didn't know if this process was part of how varroa tolerate amitraz exposure.”

— Julia Fine, Research Entomologist, USDA Pollinator Health Research Laboratory (Journal of Apicultural Research)

“Our study shows that we can increase amitraz's killing power by 50% when used in combination with another compound — a synergist — that weakens the mite but doesn't cause harm to bees. This research aims to provide beekeepers with practical tools and strategies that they can implement to effectively control varroa mites, especially since these mites become increasingly resistant to our limited arsenal of bee-safe pesticides like amitraz.”

— Sascha Nicklisch, Assistant Professor, UC Davis Environmental Toxicology (Journal of Apicultural Research)

What’s next

The researchers note that the next step is to develop synergists that specifically inhibit the mite's ability to tolerate amitraz without affecting honeybees.

The takeaway

This research offers a promising new approach to help beekeepers more effectively combat the destructive varroa mite and protect their critical honeybee colonies, which play a vital role in U.S. agriculture worth over $20 billion annually.