The surprising reason bees replace their queens

This replacement process, known as supersedure, begins when thousands of worker bees sense that their queen is no longer producing enough eggs. Acting together, they begin raising a new queen to take her place. While this mechanism helps wild colonies adjust to shifting conditions, it can create complications in managed hives. Interruptions in egg laying, declining colony strength and reduced pollination or honey output often follow.

What Triggers a Queen's Downfall

Researchers at the University of British Columbia have now uncovered a key reason behind these coordinated overthrows and how they unfold so precisely.

In work recently published in PNAS, the team reports that common viruses can cause a queen's ovaries to shrink. This reduces her ability to lay eggs and also lowers her production of methyl oleate, a pheromone that normally signals to workers that she is healthy. When levels of methyl oleate fall, workers detect the change and begin preparing to replace her.

"A healthy queen can lay as many as 850 to 3,200 eggs per day, which is more than her whole body weight," said senior author Dr. Leonard Foster, a professor of biochemistry and molecular biology at UBC's Faculty of Medicine and Michael Smith Laboratories. "But in our experiments, virus-infected queens laid fewer eggs and produced less methyl oleate. That pheromone reduction seems to be the signal to workers that a queen is no longer fit to continue."

Why Queen Health Matters for Global Food Security

Bees are responsible for pollinating roughly one-third of the crops grown around the world, making their health critical for food systems, food security and communities everywhere.

For years, beekeepers have noted increasing issues with queen failure and early supersedure. Recent surveys identify "poor queens" as the most common explanation for overwintering losses. The new findings point to viral infections as a major contributor to these failures, disrupting the pheromone-based communication that keeps colonies functioning smoothly.

A Potential Tool for Beekeepers

The research also offers a promising option for beekeepers looking to stabilize their hives. In initial field trials, colonies that received synthetic pheromone blends containing methyl oleate were far less likely to begin rearing replacement queens than colonies given blends without it.

"That could be a big deal for beekeepers," said Dr. Foster. "Supersedure can be disruptive and costly, but supplementing colonies with methyl oleate could help stabilize hives during periods when continuous productivity is most important."

These results suggest new management strategies that could be particularly valuable during peak pollination or honey production, when losing a queen can severely affect a colony.

Viruses, Varroa Mites and Hidden Threats to the Queen

"Our research really emphasizes how virus infections in queens can be a major problem for beekeepers," said first author Dr. Alison McAfee, a research associate at UBC's Michael Smith Laboratories and North Carolina State University. "Previous studies showed that failing queens were heavily infected with viruses, and now we know that those infections can lead to supersedure, which is risky for the colony and expensive for beekeepers to manage."

The study also underscores the role of varroa mites, parasitic pests that spread many of the viruses tied to queen failure. Their impact highlights the importance of maintaining healthy, parasite-free colonies.

Queen infections have not received the attention they deserve, Dr. McAfee noted, and she hopes these findings help change that understanding.

"Keeping the queen healthy is one more reason why it is so critical to think ahead and keep varroa levels under control," Dr. McAfee added. "There is currently no treatment for viruses in honey bee colonies, but now that we better understand their impact, we can change the way we manage varroa to give the queen a better chance."