Southern California Bees Fend Off Deadly Mites

UC Riverside study finds local hybrid honeybees carry far fewer Varroa mites than commercial colonies.

Apr. 12, 2026 at 6:07pm

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An abstract, highly structured painting in earthy tones of green, brown, and ochre, depicting the intricate interplay of geometric shapes, waveforms, and botanical spirals, representing the complex dynamics between honeybees and the Varroa mite parasite.A conceptual visualization of the complex relationship between honeybees and the Varroa mite parasite, offering clues for more sustainable beekeeping practices.San Diego Today

Researchers at the University of California, Riverside have discovered that a locally adapted hybrid honeybee population in Southern California carries significantly lower Varroa mite infestations compared to commercial bee colonies under the same management conditions. The study found that the Californian hybrid bees had 68.3% lower mite intensity and were less likely to cross treatment thresholds, providing clues for healthier, more sustainable beekeeping.

Why it matters

Varroa mites are one of the biggest threats facing honeybee populations across the United States, contributing to annual colony losses as high as 62%. This discovery of mite-resistant traits in a regional bee population offers hope for reducing reliance on chemical treatments and supporting the long-term health of pollinator populations critical to agriculture.

The details

The UC Riverside researchers monitored 236 colonies from 2019 to 2022, finding that commercial colonies averaged 4.83 mites per 100 adult bees, while Californian hybrid colonies averaged just 1.26 mites per 100 bees. In lab experiments, the team also discovered that Varroa mites were significantly less attracted to larvae from the Californian hybrid bees compared to commercial bee larvae, suggesting the resistance mechanism may be genetically encoded.

  • The study was conducted from 2019 to 2022.
  • The findings were published in the journal Scientific Reports in April 2026.

The players

Genesis Chong-Echavez

A UC Riverside graduate student and lead author of the study.

Boris Baer

A UC Riverside entomology professor and co-author of the study.

UC Riverside's Center for Integrative Bee Research

The research team that conducted the long-term monitoring of Varroa mite infestations in honeybee colonies.

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What they’re saying

“This question did not start in the lab. It started in conversations with beekeepers. They were not just observers; they helped shape the questions behind this research.”

— Boris Baer, UC Riverside entomology professor

“What surprised me most was the differences showed up even at the larval stage. This suggests the resistance mechanism may go deeper than some kind of behavior and may be genetically built into the bees themselves.”

— Genesis Chong-Echavez, UC Riverside graduate student

What’s next

The research team now plans to examine the genetic, behavioral, and chemical signals that may make the Californian hybrid bee larvae less attractive to Varroa mites, with the goal of identifying traits that could support breeding programs to reduce treatment needs and improve colony health.

The takeaway

This discovery of mite-resistant traits in a regional honeybee population offers a promising path forward for more sustainable beekeeping practices, reducing reliance on chemical treatments and supporting the long-term health of critical pollinator populations.