Worker honey bees can sense infections in their queen, leading to revolt

When the results of the Canada’s national honey bee colony loss survey were published in July 2025, they came as no surprise. According to the Canadian Association of Professional Apiculturists, an estimated 36 per cent of Canada’s 830,000 honey bee colonies had perished over the winter.

These figures used to make headlines. But after almost two decades of the same story ― colonies dying in the winter, beekeepers struggling to rebuild, somewhat succeeding, rinse and repeat ― the sad statistics are no longer news, and we are still working out why the cycle persists.

Now, we might be having a light-bulb moment. My colleague Abigail Chapman and I recently found that queen honey bees are infected with viruses that compromise their fertility and may get them ousted from their colonies. And that’s meaningful, because “poor queens” is the top-ranked cause of colony losses reported by Canadian beekeepers.

The life of a queen

A typical honey bee colony has a single queen at the helm, and she is solely responsible for laying thousands of eggs per day ― more than her own body weight ― to grow and replenish the colony’s population for years.

A healthy, productive queen also secretes pheromones that, like a chemical bouquet, signal her quality to the workers (sterile females who make up most of the colony’s population).

The queen cannot afford to get sick. She already barely has time to sleep, and the colony depends on her to remain reproductive. But she may indeed become sick.

Queen “autopsies” point to viruses

Our surveys of queens from members of the British Columbia Bee Breeders’ Association showed that “failing” (poor quality, unproductive) queens had a higher viral burden than their healthy counterparts. That is, they were either infected with more viruses, had more intense infections, or both. The failing queens also had smaller ovaries, a sign they could be less fertile.

But this doesn’t necessarily mean that viruses were the culprit or that queens were sick, per se. They could have been failing for other reasons that also made them more susceptible to infection.

So, Chapman designed an experiment to take a closer look. She infected queens with two common honey bee viruses, then measured the queens’ egg-laying activity and the mass of their ovaries.

Not only did the infected queens lay fewer eggs per day, they were less likely to lay eggs at all when compared with controls, at least during the monitoring period, despite all queens laying normally before the experiment. When we saw that the infected queens also had shrunken ovaries, just like the queens supplied by B.C. beekeepers, we knew we were onto something.

In the apiary, too, infected queens had problems. The worse a queen’s infection was, the more likely her workers were to begin rearing a replacement ― a process known as “supersedure.” If the upcoming replacement queen reaches adulthood, she will normally duel any other queen to the death, mate and become the new conveyor of eggs.

The workers’ dilemma

Superseding colonies are over three times more likely to perish when compared with healthy colonies, in part because there is no guarantee that the new queen will successfully mate. But from the workers’ perspective, supersedure is a necessary risk. If the old queen is compromised, producing a new one is the colony’s best chance at survival.

Normally, the queen produces and secretes a retinue pheromone — a blend of at least nine different chemical components — that, among other functions, inhibits workers from replacing her if all is well. But if one or more of those cues is disrupted by a viral infection, that could act like a red flag, we reasoned, signalling to the workers that the queen can’t lay her weight.

Our new data shows that this is the very process underlying the workers’ drive to replace infected queens. The infections caused a deficiency in methyl oleate ― one flower in the queen’s bouquet. This change encourages the workers to begin raising a new queen.

From beekeeper to queenkeeper

This validates beekeepers’ reports of having “queen issues” when infection levels are high and supports murmurs of queens not lasting as long as they used to. There are many other reasons why a queen may sputter, including pesticide exposure, extreme temperatures, poor mating and more. But viruses are a universal problem, and we did not previously understand the extent to which they could compromise queens.

Now that we do, colonies can be managed differently to better support the queen. There are currently no treatment options for honey bee viruses and there is a real need for commercial products, but luckily, there is still a way to act. Viruses are spread and sometimes amplified by varroa, a parasitic mite that can thankfully be controlled.

Read more: Deadlier than varroa, a new honey-bee parasite is spreading around the world

Varroa treatments ― which must be conducted two to three times per year to keep colonies alive ― already keep beekeepers up at night. Some may want to surrender at the thought of needing to be even more diligent.

But until an antiviral is developed and brought to market, stepping up varroa control is likely the best defence for keeping queens healthy and bringing down colony losses. Pollination of our fruits, nuts and seeds will depend on it.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Alison McAfee, University of British Columbia; North Carolina State University

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Alison McAfee receives funding from Project Apis m. She is affiliated with the Canadian Association of Professional Apiculturists and the British Columbia Honey Producers' Association.