Practical Guide: 2.4 Chalkbrood

Chalkbrood is a fungal disease that affects worker and drone brood. Contamination by spores occurs through larval feeding. The fungus germinates in the larval gut and spreads throughout the body in the form of filaments. The disease occurs mainly in weak colonies; it is promoted by sharp drops in temperature and high humidity. It may affect individual colonies or, under unfavourable weather conditions (cold, humidity), entire apiaries in the form of an epidemic. A site that is regularly and heavily affected by chalkbrood is considered unsuitable; hives should therefore be relocated to a sunnier location. Severe infestation can kill colonies.

Official Factsheet (BGD / SSA) – Summary

Factsheet: 2.4 Chalkbrood

• Description: Chalkbrood is a fungal disease in which fungal spores are ingested with food. They germinate in the larvae’s intestine and form a mycelium that invades the entire body, resulting in dry, chalk-like mummies. :contentReference[oaicite:3]{index=3}
• Symptoms: Brood mummies appear on the landing board or at the bottom of the hive early in the morning. When shaking the frames, the mummies rattle in the cells and the brood pattern appears patchy. :contentReference[oaicite:4]{index=4}
• Light infestation – Measures:
  • Remove affected frames or isolate them.
  • Stimulate the bees’ cleaning behaviour.
  • Avoid chilling of the brood.
• Severe infestation – Measures:
  • Create an artificial swarm and place it in a clean hive with new foundation.
  • Melt down contaminated frames.
  • Replace the queen to reset the sanitary status.
  • Weak colonies: unite or eliminate depending on their condition.
• Prevention & Location:
  • Choose a dry and warm apiary location to reduce humidity that favours the disease.
  • Do not exchange frames containing mummies with other colonies.
  • Ensure good nutrition and proper thermal regulation of colonies.

► PDF of the official factsheet (FR)

► Official factsheet page (abeilles.ch)
Note: section Bee health / Diseases and pests → 2.4 “Chalkbrood”. :contentReference[oaicite:5]{index=5}

Summary based on factsheet 2.4 (V 2206). Last verification: 01/2026.

See also:

• Factsheet: 1.4.3 Artificial swarm with queen
• Factsheet: 4.4.1 Melting frames
• Renewing colonies and queens
• Factsheet: 4.7.1 Uniting colonies