One of the first signs many beekeepers notice is the presence of small white or gray mummified larvae near the hive entrance or on the bottom board.

If you inspect the hive, you may also find signs of chalkbrood by:

White or gray larvae that have dried into hard “mummies”
An irregular brood pattern
Empty cells where larvae once developed
Chalk-like remains removed from the brood nest by worker bees

For many beekeepers, chalkbrood is one of the first indicators that something inside the colony isn’t functioning quite as it should.

Chalkbrood is caused by the fungus Ascosphaera apis, which infects young honeybee larvae.

At the same time, the disease is often associated with more than just the fungus itself. Chalkbrood tends to appear more frequently in colonies that:

Experience excess moisture or poor ventilation
Are weak or under stress
Struggle to keep brood warm during cold periods
Face other challenges that disrupt the colony’s balance

For that reason, many experienced beekeepers view chalkbrood as a symptom of an underlying issue rather than the root problem itself.

A small outbreak doesn’t necessarily spell disaster.

Strong colonies can often remove infected larvae on their own and recover without significant intervention.

However, if the problem becomes severe, chalkbrood may:

Reduce the number of young bees successfully emerging
Slow colony development
Lower honey production
Make the colony more vulnerable to other health challenges

In extreme cases, a colony that is already weak may struggle to recover.

Yes.

The fungal spores can spread from one colony to another through several different pathways, including:

Robbing between colonies
Moving infected frames
Shared equipment
Bees drifting between neighboring hives

Because of this, it’s always wise to be cautious when transferring equipment or comb from colonies where disease is suspected.

Yes.

Chalkbrood is not known to infect humans, and honey from an affected colony is generally considered safe to consume.

For beekeepers who harvest bee brood as food, it may still be wise to avoid using larvae from colonies where disease is present or suspected. Healthy, thriving colonies are usually the better choice.

The fungus responsible for chalkbrood cannot grow in honey due to honey’s low moisture availability and naturally high sugar concentration.

As a result, chalkbrood is primarily a problem for the colony itself, not for the safety of the honey.

Strengthening the colony is often the most important step.

Depending on the situation, it may help to:

Improve hive ventilation
Reduce moisture issues
Replace old or heavily contaminated comb
Ensure the colony has adequate food stores
Support weak colonies so they can build strength
Consider requeening if the problem returns year after year

Many beekeepers find that chalkbrood naturally declines once colonies become stronger and conditions improve.

Try to see chalkbrood as a signal rather than the actual problem.

When signs of chalkbrood appear, try not to focus solely on the mummified larvae. Instead, start asking questions like:

Is the colony strong enough?
Has the weather been unusually cold or damp?
Are food stores sufficient?
Is the hive located in a suitable spot?

More often than not, chalkbrood is telling us that the bees need slightly better conditions to do what they do best.

Like many challenges in beekeeping, the goal isn’t simply to fight the problem. It’s to understand why it appeared in the first place.

Have you ever encountered chalkbrood in one of your colonies – did you find out what turned out to be the underlying cause in your apiary?

Fredrik 🐝