New Research Shines Light on What’s Behind Honey Bee Losses

The latest research findings from USDA’s Agricultural Research Service (USDA-ARS) is shedding light on the causes behind the catastrophic honey bee colony losses reported by commercial beekeepers earlier this year. The findings point to alarmingly high levels of viral infections—vectored by Varroa destructor (Varroa) mites with resistant genes to a common treatment—as key drivers of colony collapse.

The study, which analyzed samples from six major commercial beekeeping operations affected by the losses, provides more detailed evidence of the biological factors behind the widespread die-offs. According to USDA-ARS, these operations managed nearly 184,000 colonies — roughly 7% of all U.S. hives. Reported losses averaged more than 60%, just as bees were being staged for California’s almond pollination season.

Researchers reportedly found high levels of Deformed Wing Virus (DWV-A and DWV-B) and Acute Bee Paralysis Virus in both pooled colony samples and individual bees showing shaking and other signs of morbidity. Experimental inoculation further confirmed these viruses as the likely cause of mortality in collapsing colonies.

“The beekeeping and bee health community appreciates the work of the USDA-ARS bee research laboratories,” says Matt Mulica, Senior Project Director at Keystone Policy Center, which facilitates the Honey Bee Health Coalition. “They quickly took samples of lost colonies and now that they’ve released the analysis, beekeepers can better understand what happened and take action.”

In addition, all Varroa mites collected from affected colonies tested positive for a genetic marker linked to resistance to amitraz, the most commonly used miticide in commercial beekeeping.

“This is a critical moment for honey bee health,” says Patty Sundberg, President of the American Beekeeping Federation. “We can’t continue relying on a single line of defense against Varroa.”

USDA-ARS researchers have submitted a manuscript for peer review. To access the full study, click here.