Chalkbrood

Chalkbrood is caused by the ascosphaera apis fungus. The fungus infects larvae and fills them with infectious spores.

Age of brood affected

Larvae 3–4 days old are most vulnerable to infection.

Both sealed and unsealed brood can become infected.

Infection method

Spores of the fungus are introduced to larvae by:

  • contaminated food
  • pollen
  • bees carrying the fungus.

Spores can be viable for 15 or more years in contaminated equipment and soil.

Symptoms

There are 2 stages of infection:

  1. Larvae take on a white, fluffy appearance. They will swell to the full dimension of the cell.
  2. Larvae change to hard, flat lumps that resemble chalk. They will darken to be a grey or black colour. At this stage, the chalky larvae produce infectious spores.

Treatment

Hives will usually recover from chalkbrood by themselves, as adult bees will clear the chalky larvae out of the cells.

To reduce outbreaks:

  1. Remove the chalky larvae from the bottom of the hive to help it recover.
  2. Clean hands and equipment between hives.
  3. Keep hives warm and dry.
  4. Do not subject the bees to nutritional stress.
  5. Re-queen your hives.

Diagnosing chalkbrood

Chalkbrood can be diagnosed by the Apiary Unit through samples of:

  • chalky larvae
  • sections of comb containing suspected chalkbrood (sent in a waterproof container).

Send samples to:

Apiary Unit
Department of Primary Industries and Regions
33 Flemington Street
Glenside SA 5065

Page last reviewed: 20 Sep 2022

 


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