Foulbrood vs Chalkbrood – Key Differences for UK Beekeepers
Last updated: 1 May 2026
Foulbrood and chalkbrood can both affect brood, but they are not the same level of concern. Foulbrood is a serious notifiable disease group in the UK, while chalkbrood is a fungal brood condition often linked with stress, damp, genetics or colony weakness.
Quick comparison
- Foulbrood: serious, notifiable if suspected or confirmed, may involve sunken cappings, abnormal larvae, unpleasant smell and colony decline.
- Chalkbrood: usually seen as white, grey or black hardened “mummies” in cells or at the entrance.
Signs that need urgent caution
Take extra care if brood appears melted, ropy, sunken, greasy, discoloured or smells unpleasant. Do not move frames or equipment between colonies if foulbrood is suspected. Compare with the bacterial diseases guide and seek advice.
Signs more consistent with chalkbrood
Chalkbrood commonly appears as hard, chalky brood mummies. These may be white, grey or dark and may be found at the hive entrance where workers remove them. Management usually focuses on improving colony strength, ventilation and queen quality.
What to do next
- Photograph suspicious brood if safe to do so.
- Do not swap frames between colonies.
- Check whether other colonies are affected.
- Use the Colony Health Triage Tool.
- Seek local association or bee inspector advice if foulbrood is possible.