The Western honey bee is a crucial ecological and agricultural pollinator. In the U.S., beekeepers face annual colony losses primarily due to parasites such as Varroa destructor. A recent study explored a hybrid population of honey bees in Southern California, comprising a genetic mix of Western European, Eastern European, Middle Eastern, and African lineages. Researchers discovered that these hybrid bees can effectively suppress Varroa levels without chemical intervention, paving the way for innovative strategies to safeguard pollinators against global stressors.
Electron micrograph of Varroa destructor (arrow) nestled between the honey bee’s exoskeleton plates. Image credit: UMD/USDA/PNAS.
The Varroa mites feed on the fatty tissues of bees, compromising their immune systems, causing weight loss, and shortening their lifespans.
The fat body in honey bees operates similarly to the liver, pancreas, and immune system in humans.
Moreover, these mites serve as vectors for severe viruses like the deformed wing virus and acute bee paralysis virus, which they introduce directly into the bee’s bloodstream.
Early studies relied on chemical treatments for control, yet these approaches often lose effectiveness over time.
“We frequently heard accounts of honey bees in California thriving with minimal chemical treatments,” stated Genesis Chong Echavez, a graduate student at the University of California.
“I aimed to rigorously test these claims and uncover the factors influencing beekeepers’ observations.”
During their research from 2019 to 2022, Chong Echavez and UC professor Boris Baer monitored 236 honey bee colonies in Southern California.
Although California bees are not entirely immune to mites, a colony led by a locally bred California hybrid honey bee queen saw a roughly 68% decline in Varroa levels. In contrast, commercial honey bee colonies had higher mite counts.
Additionally, colonies with these queens were more than one-fifth less likely to exceed mite levels that would necessitate chemical treatment.
To further investigate honey bee resistance to mites, the researchers also performed lab experiments on developing honey bee larvae.
Since Varroa mites must invade reproductive cells to breed, the scientists assessed whether they were equally attracted to larvae from commercial and hybrid honey bee colonies. The results showed a stark difference.
California hybrid honey bee larvae attracted fewer mites during their seventh day of life, which is typically when mites are most vulnerable.
This finding indicates that the key to honey bees’ ability to resist mites may lie in their early development stages, prior to adult exposure.
“What surprised me the most was the differences observed even in the larval stage,” Chong-Echavez remarked.
“This hints that the resistance mechanism may be deeply embedded in the genetic makeup of the bees.”
The full results are published in the journal Scientific Reports.
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G. Chong-Echavez & B. Baer. 2026. Varroa Mite resistance in hybrid honey bee (Western honey bee) populations of Southern California. Scientific Reports 16, 10952; doi: 10.1038/s41598-026-45759-9
Source: www.sci.news
