Key points
- A fungal brood disease caused by Ascosphaera apis.
- Typical sign: hard white or grey-black "mummies" on the floor and in front of the hive.
- Favoured by damp, cold and weak colonies.
- No authorised treatment: ventilation, strong colonies and hygienic queens.
Chalkbrood is a very common fungal disease. It rarely kills the colony, but a heavy case slows its spring build-up.
The agent
Larvae become infected by swallowing Ascosphaera apis spores with their food. The fungus grows in the gut, then invades the whole larva, which dies after capping1. Spores remain infectious for a very long time in wax and equipment.
Symptoms
- Dead larvae hardened like chalk: the “mummies”.
- White mummies, or grey-black ones once the fungus has fruited.
- Mummies that rattle when the frame is shaken.
- Mummies on the floor, on the landing board and in front of the hive.
- Spotty brood with cappings pierced or removed by the bees.
What favours the disease
The fungus takes advantage of chilled brood: cold, damp springs, shaded or poorly ventilated hives, colonies too weak to cover their brood. A line’s low hygienic ability also plays a major role1, 2.
What to do
- Place hives in a dry, sunny spot and ensure good ventilation.
- Keep colonies strong; unite weak ones.
- Remove the worst-affected combs and replace old combs regularly.
- Requeen with a line selected for hygienic behaviour.
No medicine is authorised against chalkbrood in the European Union3.
References
- Aronstein K.A., Murray K.D. (2010). Chalkbrood disease in honey bees. Journal of Invertebrate Pathology 103: S20-S29.
- Jensen A.B. et al. (2013). Standard methods for fungal brood disease research. The COLOSS BEEBOOK, Vol. II. Journal of Apicultural Research 52(1).
- FAO, IZSLT, Apimondia, CAAS (2021). Good beekeeping practices for sustainable apiculture. FAO Animal Production and Health Guidelines No. 25.