Mummified Brood? How to Recognize and Deal With Chalkbrood Infections

Published on August 21, 2020

A beekeeper inspects a bar for chalkbrood infections

Check your brood comb for chalkbrood infections

Picture this: You go to check on your bees and notice something odd at the entrance to the hive. There are small, dried up, chalky white and grey objects sprinkled around the hive entrance. These mummified pupae are one of the signs you have a chalkbrood infection, and it’s also a sign your bees are doing their best to take care of the problem. But, what is this strange disease that leads to something out of a beekeeping horror movie?

Chalkbrood mummies outside the hive entrance

Mummies outside or inside your hive are one sign you have a chalkbrood infection on your hands

What Is Chalkbrood?

Chalkbrood is caused by a fungus, Ascophaera apis. This disease, not unlike American foulbrood, directly impacts the brood in your colony and not the adult workers.

However, a chalkbrood infection can make it hard for your colony to stay healthy, and ultimately leaves it more vulnerable to stressors and other diseases. It’s not something to dismiss. In fact, without healthy brood, your colony cannot survive.

How Does It Spread?

Chalkbrood spreads primarily in the spring but can infect a colony throughout the busy season. Typically, it occurs in conditions that are moist and poorly ventilated. Workers can pick up fungal spores on pollen and bring them back to the hive after foraging, or, robbers bees can bring spores into neighboring hives.

This fungal infection takes hold when spores mix with brood food. When workers feed contaminated brood food to the larvae, the fungus outcompetes the bee babies for food, leaving them malnourished and unable to complete their developmental cycle. Instead, they start to turn chalky and grey, eventually turning black when the infection is in full force.

When the pupae turn black, the fungus is able to use its fruiting bodies to produce and release spores; this is when it is most infectious. Like many bee diseases, spread occurs as a result of bees mixing and mingling with other colonies during activities such as foraging and hive robbing.

How Do You Recognize Chalkbrood Infections?

Your first line of defense against chalkbrood infections are quality inspections. You don’t know you have an infection unless you look. When you inspect your colony, look for these telltale signs of chalkbrood:

Patchy brood pattern
Exposed, discolored pupae in open brood cells
Perforated brood cells
Hard larvae inside the brood cells
Chalkbrood mummies at the entrance or in the bottom of the hive

If you want to do a fascinating test to check for chalkbrood infections, try this:

Remove a bar of comb during your inspection.
Gently shake the bar, listening carefully.
If you hear a rattling noise, it can indicate the presence of hardened, chalkbrood-infected pupae shaking around in capped cells.

If you spot any of these signs, there’s no need to panic. Fortunately, chalkbrood infections are usually contained by the colony and resolve on their own.

Will Chalkbrood Destroy My Colony?

Short answer: no. Chalkbrood infections are typically not fatal, however, there’s a big caveat with this: Any infection in your colony deserves your attention as it can be a sign the colony is not as healthy as it needs to be in order to survive and thrive.

Think about it this way. Have you ever had an infection and ended up with a secondary infection on top of it? It’s not uncommon for an upper respiratory infection to turn into raging pneumonia, for example. It’s similar with bees. Even if the initial infection (chalkbrood, in this case) is manageable, it can predispose the bees to additional diseases that are harder for the bees to take care of themselves.

Additionally, a chalkbrood infection that takes hold and festers can be a sign your colony doesn’t have a baseline of health and might be suffering under the weight of stressors, such as erratic weather patterns, nutritional deficiencies, and competition from other bee species. Malnourished bees tend to struggle, so a good understanding of nutrition will benefit your beekeeping in the long run.

If you want to know more about honey bee nutrition, I wrote a series about this summer. Learn the basics about:

Honey

Pollen

Water

But, I bet you want to know what you can do about chalkbrood infections in the meantime.

What You Can Do About Chalkbrood Infections

Check your brood comb for chalkbrood infections

Here’s the good news. If your bees have good hygiene habits and the colony is otherwise healthy, they should take care of this infection themselves by meticulously removing infected pupae and cleaning the hive.

However, there are actions you can take to ensure chalkbrood is just a blip in an otherwise enjoyable beekeeping season.

First of all, make sure your hive is well-ventilated. Our Beepods Top Bar Hive comes vented to prevent the accumulation of excess moisture. Make sure your hive is sited properly, with the entrance facing the sun to minimize cold, damp conditions. Additionally, be aware of how you contribute to temperature fluctuations in the hive by taking note of these pointers:

Don’t remove adult bees from the hive
Reduce the volume of the brood chamber in winter
Don’t give your colony extra brood to rear
Be cognizant of when you’re adding extra bars
Minimize inspections during days with damp or cold weather

Finally, if you suspect a chalkbrood infection, clean your tools thoroughly before using them on multiple colonies. Better yet, use different tools for infected and non-infected colonies.

Final Thoughts

Healthy bees are your best defense against chalkbrood infections. When you check on your bees regularly, make sure they have the resources they need (quality forage, access to water, ventilation, protection from pests, and shelter from inclement weather). If your bees are already healthy, chalkbrood is more likely to be a messy house that just needs to be cleaned rather than a tornado that tears the whole thing down.

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Caitlin Knudsen

Caitlin Knudsen is a content writer for Beepods with a passion for lifelong learning and psychology. She is an avid gardener, grower of houseplants, and does recipe development and food photography in her spare time.