Call it the case of the mysterious disappearing honeybee.

When many beekeepers nationwide cracked open their hives after hibernation this winter, they found losses that frequently exceeded anything they’d seen before.

University and USDA Agricultural Research Service scientists are examining samples sent in by beekeepers to try to determine the cause or causes of the losses. But it’s a complicated task, said Danielle Downey, executive director of the nonprofit Project Apis m. (PAm) honeybee research organization.

“The colonies looked like they were recently very strong and had food and brood,” she said. “What was a healthy, strong colony had adult bees leave that didn’t come back, so there’s something wrong that causes the really quick decline.”

The bee population decline couldn’t have come at a worse time for almond growers, many of whom said they noticed poorer performing hives during pollination.

Dave Phippen, a partner in the family-owned grower-huller-sheller Travaille & Phippen near Manteca, was one of those. While they were able to secure enough hives from the three different beekeepers they historically use, he questioned the quality.

“Two had challenges, and I think brought from sources we don’t usually deal with,” he said. “I think it was pretty clear that not all of the bees were up to speed.”

And the Survey Says…
When beekeepers first began reporting high mortality rates this winter, PAm quickly sent out a survey to gauge losses. The response was unprecedented, with beekeepers representing about 68% of the nation’s hives participating.

The survey found responding commercial beekeepers (those with 500 or more colonies) averaged 62% losses.

Sideliner operations with 50 to 500 colonies reported an average of 54% losses while hobbyists with 1 to 49 colonies reported an average of 50% losses. The results also reversed recent trends where commercial beekeepers generally experienced lower losses than smaller-scale producers.

All told, beekeepers reported losing more than 1.1 million hives over a short period of time, according to survey results.

Combined with normal bee mortality during other times of year, the additional loss puts many beekeepers at a loss rate of 70% to 100% over the past 12 months, according to PAm figures.

That compares to an estimated annual loss of 55% reported during the 2024 U.S. Beekeeping Survey. Conducted by the Apiary Inspectors of America and Auburn University, the online survey in May 2024 asked beekeepers about their losses from April 1, 2023, to April 1, 2024. About 1,650 beekeepers with 337,134 colonies on Oct. 1, 2023, responded. They represented about 13% of the nation’s 2.51 million managed honey-producing colonies.

For the year-long reporting period, the 55% loss rate was the highest since 2010-11 when annual losses were first determined. It was also 14.8% higher than the running 13-year average annual loss rate of about 40%.

In a follow-up PAm survey this year, Downey asked beekeepers about many of their husbandry practices to try to correlate them with losses. So far, nothing stands out, she said.

The losses will likely reverberate through the beekeeping industry not just this season but in ones to come, Downey said. Beekeepers also will have to decide whether they want to rebuild without any guarantees that the same thing won’t recur.

“There’s no certain recipe for success,” she said. “We don’t know what’s going on and the catastrophic losses could happen again.”

Because of the high-quality pollen produced by almond trees, bees typically are at their strongest as they come out of almond pollination. If hives weren’t able to recover this spring, some in the industry worry about the 2026 almond pollination season. That’s because how well hives come out of hibernation in January 2026 depends on their health going in this winter.

Almond Pollination Season
News about honeybee losses broke in January as beekeepers began opening and checking their hives before moving them into California almond orchards. The state’s almond industry typically requires about 2.4 million hives to pollinate the crop for a six-week period. Because the state only has about 840,000 resident colonies, out-of-state beekeepers bring in another roughly 1.5 million hives.

Ryan Burris, a beekeeper and queen producer in Shasta County, doesn’t truck his bees cross country, instead serving almond growers in the northern Sacramento Valley. Burris also doesn’t like to open his hives in the winter because it stresses the bees by breaking up the clusters they form to keep warm.

When he did open them to add protein patties before moving them into almonds, he was surprised at the lower bee numbers.

“I had more hives than normal that were underperforming, but I didn’t have the massive die-offs that some people had,” said Burris, president of the California State Beekeepers Association. “I’m a queen breeder and I don’t run as many hives. I know for a fact that a lot of the guys who run 5,000, even 40,000 hives, had big losses or super big losses, and it’s attributed to so many different things.”

Almond grower Phippen in the past had a company test hive strength using a sensor to measure heat radiated by the bees so beekeepers didn’t have to open boxes. But the company went out of business two years ago, and he hasn’t had hive quality tested since then.

“I really liked that service,” Phippen said.

Although he doesn’t have any documentation, Phippen suspected some of the hives billed as eight frames this year likely were smaller.

“We’re pretty sure some of the bees weren’t up to snuff and didn’t do great pollinating,” he said.

Wrangler Wheeler, who farms almonds and alfalfa west of Modesto with his father, Dave, said they received the same number of hives as last year from their long-standing Northern California beekeeper, and the insects seemed to be good quality. But Wrangler said he received calls from several panicked colleagues who were short hives and wondered if he knew of anybody with extras. He referred them to his bee broker.

“That close [to pollination], it’s kind hard to find bees,” Wrangler said.

Theories Abound
Theories currently abound about the cause of the bee losses, and it may be a combination of factors, too. Burris has his own ideas.

Typically, in January, beekeepers open their hives to evaluate their size. A four-frame hive should have grown to six to eight frames in time for almond pollination. This year, he said many beekeepers found the four-frame hive had shrunk to two frames.

“The bees didn’t grow well,” Burris said. “Mites and viruses coupled with poor nutrition–the bees just didn’t grow like people were used to seeing.”

He also didn’t rule out poorly timed pesticides, including insect growth regulators that don’t kill adult bees but affect the next generation, as part of the cause.

Downey said one of the unusual symptoms many beekeepers reported in the survey was the lack of deadouts, or when entire colonies die.

Some beekeepers also theorized that the extreme weather in the Midwest and South during 2024 may have played a role. The central part of the country was hit with a prolonged drought, which reduced wild forage crops for the bees during the summer and fall. Then sub-freezing winter temperatures and snow hit parts of the country as far south as Florida, further stressing hives.

Currently, scientists are assaying samples for pesticide residue and viral infections. Varroa mites (parasites with vampire-like traits because they suck bodily fluid from bees) can weaken or kill adult bees and pupae. They also can vector numerous viruses, including deformed wing virus, acute bee paralysis virus, Kashmir bee virus and Israeli acute paralysis virus.

Parasitic mite syndrome has been found in conjunction with high varroa infestations, although the causative agent is unknown. The syndrome has a range of symptoms including spotty brood pattern, sick brood that appears sunken or melted into the cell, lack of eggs or developing larvae, rapidly decreasing adult populations and bees with deformed wings.

Most beekeepers treat their hives for varroa mites, but the pest appears to be growing resistant to the one registered control: Amitraz. As part of testing, researchers will screen mites for resistance levels.