Scientists Identify Culprit Behind Biggest Ever U.S. Honey Bee Die-Off

U.S. beekeepers had a disastrous winter. Between June 2024 and January, a full 62% of commercial honey bee colonies in the United States died, according to an extensive survey. It was the largest die-off on record, coming on the heels of a 55% die-off the previous winter.

As soon as scientists at the U.S. Department of Agriculture (USDA) caught wind of the record-breaking die-offs, they sprang into action—but their efforts were slowed by a series of federal funding cuts and layoffs by President Donald Trump’s administration. Now, 6 months later, USDA scientists have finally identified a culprit.

According to a preprint posted to the bioRxiv server this month, nearly all the dead colonies tested positive for bee viruses spread by parasitic mites. Alarmingly, every single one of the mites the researchers screened was resistant to amitraz, the only viable mite-specific pesticide—or miticide—of its kind left in humans’ arsenal.