It was a disastrous winter for beekeepers in the U.S. Between June 2024 and January 2025, more than 60 percent of commercial honey bee colonies perished, according to a survey.
It’s the largest decline in honeybee population the country has ever seen.
In response, the U.S. Department of Agriculture quickly sprung into action. However, their efforts were hampered by a series of layoffs and federal funding cuts.
Fast forward to July and they have finally identified the culprit behind the massive honey bee die-off.
According to scientists, nearly all the colonies that collapsed tested positive for bee viruses spread by parasitic mites.
Even more concerning, all of the mites were found to be resistant to Amitraz—the only pesticide currently effective against them.
They were able to identify the mites after combing through the dead honey bee colonies.
A group of researchers at USDA’s Bee Research Laboratory collected dead bees from over 100 affected colonies across the country, as well as samples of honey, pollen, and wax.
The samples were then taken to labs, where their RNA and DNA were extracted and analyzed for bacterial or viral genetic material. The DNA from recovered varroa mites was also sequenced to look for mutations related to pesticide resistance.
Danielle Downey, the executive director of Project Apis m., the non-profit that conducted the recent survey, said “there is a lot at stake.”
For years, miticide-resistant varroa mites have been an issue for beekeepers. Since the 1980s, many have evolved to become resistant to four major types of miticide.
Unfortunately, new pesticides are difficult to develop and Amitrax was one of the best remaining options. However, current evidence suggests that it may no longer be effective.
Aaron Gross, a toxicologist, is concerned about the study’s findings. He explained that Amitraz is widely considered to be one of the safest options, though it can still can weaken colonies over time if used in high doses.
Losing Amitraz would be a hard blow as the alternatives are typically less effective or much harsher.
Experts say that while viruses transmitted by mites likely delivered the final blow, other factors, such as poor nutrition and pesticide exposure, may have weakened the colonies and made them more vulnerable to disease.
In the coming weeks, the USDA is expected to release an analysis of miticide residues found in the collapsed colonies.
