What Is Chalkbrood? Symptoms + Prevention

A beekeeper collecting honey and inspecting the brood for diseases like chalkbrood

Chalkbrood is a disease that affects honey bees and can devastate their population. Caused by a fungus called Ascosphaera apis, it is one of the most common diseases of honeybees worldwide.

Chalkbrood can kill entire colonies, so it’s important to know what it is and how to prevent it from overwhelming your hives.

What are the symptoms of chalkbrood?

The symptoms of chalkbrood can vary depending on the stage of the infection and the severity of the case. Some common symptoms include:

  • A white, chalky covering on larvae is an early warning sign.
  • Black or gray fungal infection can be seen at later stages of the disease.
  • Shrunken, mummified larvae are found in brood cells and other parts of the hive.
  • A sour, foul-smelling odor coming from the hive.
  • Noticeable declines in the number of adult bees in the hive.
  • Decreased honey production and other hive products.
A top-down image of brood with chalkbrood
Brood showing signs of chalkbrood.

How does chalkbrood spread?

Chalkbrood spores are highly infectious and spread via foraging bees carrying contaminated pollen. The sticky fungal spores can also be spread via drifting bees, air currents, queens, or on beekeepers’ equipment, such as bee brushes or hive tools.

What can beekeepers do to prevent chalkbrood?

The best way for beekeepers to keep their hives safe from chalkbrood is by taking preventive measures before an outbreak occurs. Recognizing early signs of infection and commencing early treatment will significantly assist the hive. Here are some tips for beekeepers to follow:

  • Check hives regularly for signs of disease: Look out for mummified larvae or white patches on combs or frames, as these could be signs of early infection.
  • Increase ventilation in your bee boxes: Good air circulation helps reduce humidity levels inside the hive, which limits the spread of fungal spores.
  • Keep hives clean: Remove debris, such as old wax comb and propolis, which could harbor fungal spores.
  • Reduce hive stress: Chalkbrood commonly impacts stressed colonies dealing with low population, bad weather, low food supplies, varroa mite infestations, and other diseases.
Chalkbrood mummies on the hive floor.
Chalkbrood mummies on the hive floor.

Lifecycle of chalkbrood

The lifecycle of chalkbrood can be divided into several stages:

  1. Fungus is introduced to the hive through spores carried on adult bees’ bodies or contaminated honey and pollen.
  2. Spores germinate and grow in the cells of the hive where bee larvae are developing.
  3. The fungus infects the larvae, causing them to develop into white, chalky-looking mummies.
  4. The infected larvae die, and the mummies remain in the cells of the hive.
  5. The fungus grows and produces spores, which can spread to other larvae and cause new infections.

The cycle continues until the infection is controlled or the hive dies.

How do you treat chalkbrood?

There are no chemical treatments for chalkbrood, so beekeepers should remove any spore sources inside, then reduce any hive stress factors.

Spotting a lot of mummies in the comb is a sign the worker bees aren’t doing their job. Requeening with a more disease-resistant stock will help.

Varroa mites are a common precursor to chalkbrood. If their population is getting too high, a course of Apistan may be required.

Check out our guides on the symptoms of European foulbrood and how to identify American foulbrood.

A starving colony will struggle to maintain a healthy, disease-free hive. In times of nectar dearth, help bees by feeding them sugar syrup or a pollen substitute.

Make sure hives are clean and well-ventilated so that there is good air circulation around them. Also, ensure that your hive boxes have a tight fit so air can’t escape easily; this will help maintain optimal temperatures within the colony.

Closeup shot of chalkbrood disease.
Closeup shot of chalkbrood disease.

Chalkbrood vs. stonebrood – what’s the difference?

Chalkbrood and stonebrood are two common fungal infections affecting honeybees. Chalkbrood primarily affects larvae in the hive, while stonebrood affects adult bees. Both may spread through contaminated food sources and on beekeepers’ hands and tools as they move between hives. Treatment options exist for both forms of infection.

What is a bee brood disease?

A bee brood disease is any disease that affects the immature stages of the honey bee, including the eggs, larvae, and pupae. Common examples include American foulbrood, European foulbrood, and chalkbrood.

Bacteria, viruses, fungi, and other parasites can cause these diseases. They can have a devastating effect on bee colonies.

The best way to prevent the spread of these diseases is to keep the hive clean and healthy and monitor for any signs of infection. If a hive gets infected, it is essential to treat it quickly to minimize the damage.

Can I use a split banana to get rid of chalkbrood?

Some beekeepers split a banana and place it on the brood frames to remove chalkbrood. This technique is simple and cheap, but we have never tried it and can’t vouch for its efficacy.

Where is chalkbrood found around the world?

Chalkbrood has been found in many parts of the world, including the United States, Canada, and Mexico.

It has also been reported in parts of Europe, including the United Kingdom, France, Germany, and Spain.

In Asia, chalkbrood has spread through China, Japan, and India. The fungus has worked its way through much of the country in Australia.

South America, Africa, and the Middle East also have this disease.

Final words

Chalkbrood is a disease affecting honey bees worldwide. It is caused by a fungus known as Ascosphaera apis, which infects larvae within a colony and spreads through contaminated pollen or nectar brought back from foraging trips.

To prevent outbreaks of this disease, it’s important to keep clean and well-ventilated hives. It would help if you also considered a breed of bees with excellent hive hygiene, such as pure Russian bees. They will quickly remove spores, and diseased larvae before the chalkbrood overwhelms the colony.

Image attribution: “Courtesy The Animal and Plant Health Agency (APHA), Crown Copyright”. Sourced from BeeBase Gallery.

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