Chalkbrood is caused by the fungus Ascosphaera apis and it affects both sealed and unsealed brood.

Appearance of Chalk Brood

At first, larvae are covered with a fluffy white fungal (mycelial) growth that looks like white mould on bread or very fine cotton wool. Larvae become swollen inside the cell. Later, the dead larvae dry out to become hard, white or grey/black chalk-like mummies.

Management practices

Management practices that reduce the stress on hives also reduce the number of chalkbrood spores. Maintaining strong healthy colonies has been demonstrated to reduce the effects of chalkbrood.

Management practices which may reduce the effects of chalkbrood disease are:

  • removing ´mummies´ from bottom boards and around the entrance
  • destroying combs containing large numbers of ´mummies´
  • supplying new combs
  • providing good ventilation in hives
  • adding young adult bees to hives
  • not allowing bees to winter in a hive that is over supered
  • feeding sugar syrup, fresh uncontaminated pollen or supplements
  • maintaining strong hives by regular re-queening
  • reducing or preventing interchange of hive materials
  • not using the same site each year – if possible shift the apiary site slightly.

Good hygiene will also help. Change clothes and disinfect smokers, boots and hive tools using chlorine bleach between apiaries or infected hives.

Spores remain viable for up to 15 years or more in equipment and soil. Use of contaminated sites and old equipment could lead to infections. Interchange of equipment by the beekeepers also spreads the disease.