Science is giving beekeepers a better way to fight colony collapse

Beekeepers across the United States are sounding the alarm. Last year, they lost over 55% of their managed colonies – the highest loss rate recorded since tracking began in 2011.This level of loss is not sustainable.

Scientists from the University of Vermont, working with international partners, have studied a new method that could help beekeepers breed healthier, more resilient honey bee colonies.

The team tested a novel tool called the UBeeO assay, designed to measure bees’ natural ability to spot and remove sick or dying young.

A growing problem for beekeepers

“Beekeepers are losing bees at a rate that they say is unsustainable,” said Samantha Alger, director of the Vermont Bee Lab at the University of Vermont and lead author of the study.

“In the ’80s, beekeepers lost colonies 10–12% of the time … but now it’s like 30–50%. Imagine that happening to someone who’s a cattle farmer or a pig farmer every year.”

While beekeepers have found ways to keep overall populations steady by raising new bees, it comes at a high cost – both in resources and in risk to wild pollinators.

When pathogens from managed hives spread to native bee populations, the health of entire ecosystems can be affected.

Alger and her team work directly with beekeepers to breed stronger, disease-resistant honey bee colonies. One focus of their efforts is helping beekeepers select for hygienic behavior – the ability of bees to detect and remove unhealthy brood from the hive.

“It’s definitely more desirable for a beekeeper to have bees that are better adapted at taking care of their diseases themselves, rather than using chemical treatments and interventions to try to reduce these pathogen loads, which, of course, may have negative impacts on the bees,” noted Alger.

A test to measure bee colony hygiene

“Now the trick is, how does a beekeeper identify a colony that is really hygienic? And there’s various tests that you can perform for that and this UBeeO is sort of a novel way of testing for it.”

The UBeeO tool, developed by researchers at the University of North Carolina at Greensboro, simulates the natural cues that honey bees use to detect sick brood.

Instead of freezing brood cells, as traditional tests do, UBeeO uses synthetic pheromones that mimic the scent of diseased or dying bees.

“UBeeO has been known to identify colonies that are able to better resist Varroa mites, but it had not been used to look at other pests or pathogens,” said Alger. “We found this new assay could be used to identify colonies that are resistant to these other stressors.”

What makes bees take action

In a typical hive, each egg laid by the queen grows into a larva, which is fed and sealed into a wax cell by nurse bees.

If something goes wrong – if the larva dies or becomes infected – nurse bees can uncap the cell and remove it. This hygienic behavior helps stop the spread of disease.

“Other folks have identified death pheromones, these compounds that are associated with death,” said Kaira Wagoner, a research scientist at UNC Greensboro and co-author of the study.

“The famous biologist E.O. Wilson was one of the first to do this. He found oleic acid was emitted from dead ants. The same thing has been found with bees, and it’s just likely a stronger signal – it’s growing as the dead brood is basically decomposing in the cell. The signals that are coming out of an unhealthy brood are different and very likely more subtle than those death pheromones.”

A more selective bee colony test

Unlike the freeze-kill test that uses liquid nitrogen to create dead brood, the UBeeO test simulates what bees would naturally encounter.

“Rather than using liquid nitrogen to kill the developing pupae or larvae, you are using a blend of synthetic pheromones that mimics the same chemicals that are emitted by dying or diseased brood,” explained Alger.

“So rather than testing the bees’ ability to identify dead brood, you are testing the bees’ ability to identify diseased brood, which means that this test is a little bit more selective and realistic to what bees experience.”

Wagoner began developing UBeeO during her doctoral studies and went on to co-found Optera, a company focused on bringing the test to beekeepers. Since becoming available in 2024, the test has been tried in over ten countries.

“It’s a really young technology,” said Wagoner. “We’ve now tested it in over 10 different countries, and there are breeding programs in at least five now, so there’s a lot more data to come.”

Bee colony test scores

To examine how well UBeeO works, scientists used it in three regions – Vermont, North Carolina, and Australia.

The bee colony test is simple: synthetic pheromones are sprayed onto a patch of brood cells, and after two hours, researchers check how many cells the bees have uncapped.

This response is scored as the UBeeO percentage. Higher scores mean more cells were inspected, which usually indicates better hygienic behavior.

The results showed that colonies with higher UBeeO scores tended to have lower levels of disease, including fungal infections like chalkbrood and parasites like Varroa mites.

“What we found, at least with this Australian dataset, is they only needed to achieve a 13% response on the UBeeO test to be really pretty resistant to chalkbrood. In contrast, colonies need to achieve a response of 55 or 60% on the UBeeO test to be resistant to mites,” explained Wagoner.

“The honey bee responsiveness largely depends on how virulent or how harmful the specific disease is to the brood. Chalkbrood kills the brood, so the bees don’t have to be as sensitive to detect it.”

The Varroa mite poses a greater challenge. These tiny invaders reproduce inside sealed cells and feed on developing bees.

If the nurse bees don’t intervene, the mites are released into the colony, spreading disease and weakening the hive. By uncapping these cells early, bees can interrupt the mite’s life cycle.

Smarter colonies without chemicals

Interestingly, the UBeeO test also detected colonies that were more resistant to Vairimorpha (formerly known as Nosema). This is a disease that affects adult bees, not brood. That raises new questions about how hygienic behavior might influence adult bee health.

“In the case of Vairimorpha, what they’re doing is kind of the mystery,” said Alger. “There might be other behaviors that hygienic colonies are performing aside of what we know.”

As researchers continue to explore these questions, the hope is that tools like UBeeO will make it easier for beekeepers to raise stronger, more self-sufficient bees – and reduce their reliance on chemical treatments.

For a profession facing some of the steepest challenges in agriculture today, that help can’t come soon enough.

The full study was published in the journal Frontiers in Bee Science.

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