Scientists at the U.S. Department of Agriculture (USDA) believe they have uncovered the cause behind a massive and alarming collapse of honey bee colonies across the country.
Their research points to deadly viruses spread by parasitic mites—mites that are now resistant to one of the most important treatments used by beekeepers.
Since early 2025, commercial beekeepers have reported losing over 60% of their bee colonies, amounting to 1.7 million hives.
These losses have cost an estimated $600 million and raised serious concerns about the impact on U.S. agriculture.
Honey bees play a vital role in pollinating crops that make up more than one-third of the country’s produce. Their work supports over $20 billion worth of crops each year in the U.S. alone.
In response to the collapse, USDA scientists collected bee samples from across California and the western states just before the annual almond pollination season in February.
The samples were analyzed by the USDA’s Bee Research Lab in Maryland, focusing on bees that showed strange behavior shortly before dying.
The researchers detected high levels of deformed wing virus types A and B, as well as acute bee paralysis virus, in nearly all the bees they examined.
These viruses are not new to science—they’ve long been known to be spread by Varroa destructor mites, a parasite that feeds on bees. But this time, the scientists found something even more troubling.
The mites collected from the collapsed colonies showed signs of resistance to amitraz, one of the most commonly used chemicals to control them. This means that treatments that once protected bees are now failing, allowing the mites to spread viruses more freely than ever before.
Joon Park, Acting Administrator of the Agricultural Research Service, emphasized the importance of the findings. He said pollinators like honey bees are essential to the food supply, and that USDA researchers are working hard to develop new strategies to manage parasites and protect bee colonies.
Dr. Judy Chen, one of the study’s lead researchers, noted that although the viruses are likely the direct cause of the bee deaths, other factors still play a role in bee health. The USDA team will continue to study bee colonies to identify additional stressors and find new ways to fight mite infections and prevent future die-offs.
Their research is currently under peer review, but a preprint is already available online, showing just how urgent this issue is for the future of food and farming.
