Cause
Stonebrood is a fungal disease. Several fungi belonging to the genus Aspergillus are associated with the disease, the most common being, A. flavus and A. fumigatus. However A. flavus is considered,
by far, the most important.

Symptoms
Both larvae and pupae are susceptible. The disease causes mummification of the affected brood. Mummies are hard and solid, not sponge-like as in the case of chalkbrood. Brood infected by A. flavus become covered with a powdery green growth of fungal spores. The spores are found most abundantly near the head of the affected brood.

Treatment
This disease is considered of minor importance and is rarely encountered. No treatment is recommended. The bees remove the dead brood on their own and the colony normally recovers in a short period of time.