Chalkbrood Disease 2: Identification and Management

Chalkbrood is common in Australan beehives despite the good hygiene of Australian bees. How do you identify, treat and manage Chalkbrood Disease?

Chalkbrood Disease is more common in the spring when the brood nest is rapidly expanding. A smaller honey bee workforce cannot maintain brood nest temperature. And ‘chilled’ brood is more susceptible to the disease.

Symptoms of Chalkbrood Disease may only appear for a short time, typically in cold and damp weather conditions.

Very cool spring weather may even cause the bees to reform their winter cluster. This leaves brood at the edges of the nest exposed to the cold. So, extra vigilance for the disease is a good idea in these conditions.

Identifying Chalkbrood Disease

  • Worker bees will uncap infected cells of dead larvae, pulling out some of the “mummies” from the comb, leaving them on the hive floor or at the entrance
  • These mummies will be hard, dry and white to grey-black in colour
  • If these mummies are present, you will need to inspect the brood frames to confirm Chalkbrood
  • Whenever possible try to perform the inspection on a fine, warm, dry day with little wind
  • After removing a brood frame, gently clear with smoke or shake away any bees so you have a full and free view of the brood
  • Look at the brood distribution. Infected hives tend to show a scattered brood pattern
  • The cell caps of dead larvae (mummies) will usually contain small holes, appear slightly flattened or be chewed away by the worker bees
  • Gently turn and shake the frame. Mummies left in uncapped cells will usually fall from the comb
  • If the infection is severe workers won’t uncap all the infected cells, in which case the mummies may be heard rattling inside the comb if gently shaken
  • If you can find an infected larva (by uncapping some cells yourself) that is not yet completely mummified , you should see that the fluffy, white fungus first erupts from its rear end

Is it definitely Chalkbrood?

There are several brood diseases to be aware of and to rule out when diagnosing Chalkbrood.

According to BeeAware, some Chalkbrood Disease symptoms can be confused with American foulbrood (AFB), European foulbrood (EFB) or Sacbrood virus. However, cells are rarely capped when EFB is present. Both EFB and AFB can be diagnosed or ruled out with a ‘ropiness test’. Sacbrood is easily identified by the fluid filled sacks that form around infected larvae.

If there are mummies present and a ropiness test does not indicate Foulbrood, then the infection is most likely to be Chalkbrood Disease.

There is another rare brood disease, Stonebrood, which also mummifies larvae. However, the colour of the Stonebrood mummies change from white to greenish instead of grey or black. Also, the fungus erupts just behind the head of the larvae, forming a collar, instead of starting from the rear end of the larva like in Chalkbrood.

How to manage Chalkbrood Disease and Prevent Spread

There is no known chemical treatment for this disease. Also, the use of chemicals is undesirable in honey production due to contamination risks. Colonies, especially strong colonies, can generally recover from the disease on their own. But there is plenty the beekeeper can do to assist:

  • Colonies should be kept warm and dry with good ventilation. Damp or overly exposed apiary sites should be avoided
  • Do not open hives unnecessarily in cool weather
  • Do not split hives or spread the brood nest too early in the season as this can result in the loss of heat from the hive
  • Only add a super to hives when really needed. The colony may have difficulty keeping the brood warm, especially if it is still building up numbers in Spring
  • Chalkbrood can still occur in warm dry conditions in summer and autumn. Limited supplies of nectar and pollen may be a factor
  • Moving hives to better nectar and pollen flows or feeding colonies sugar syrup, pollen and protein supplements can help a hive recover from an outbreak
  • While high protein pollen is preferred, any pollen is better than none at all.
  • Ideally, the bees should have access to pollen from several plant species for a balanced, nutritious diet (Bee2Bee’s West Australian Irradiated Pollen is sourced from multiple locations for this reason)
  • Re-queening may help. Colonies with queens bred for hygienic behaviour uncap cells and remove diseased larvae from the hive more readily than other lines of queens
  • Such colonies may remove diseased larvae before they become mummies, which may help to reduce the severity of the disease
  • Removing discarded mummies from the hive bottom board and at the hive entrance yourself may also help
  • Removing heavily infected combs and replacing them with foundation can also help. However, if conditions are poor the bees may not readily draw the foundation

The Australian Beekeeping Guide emphasises that Chalkbrood “can be a bit of a soul destroying bee disease” because it can just turn up in the brood, and even be severe, in spite of good hive management practices. The spores are very resistant and are known to remain infectious for at least 15 years, inside or outside a hive. They can be spread in many ways. So just remember that a Chalkbrood infection and/or its persistence does not mean you are a bad beekeeper!

Adapted from BeeAware and the Australian Beekeeping Guide.

Chalkbrood Disease mummies at hive entrance
The entrance to this beehive is littered with chalkbrood mummies that have been expelled from the hive by hygienic worker bees. Photo by Jeff Pettis used under Creative Commons Attribution 3.0 United States license.