Glossary
A rare fungal disease of honey bee brood caused by several Aspergillus species (primarily A. flavus, A. fumigatus, and A. niger). Infected larvae are colonized by fungal mycelium, turning them into hard, stone-like mummies. Stonebrood is uncommon in well-managed apiaries but can be a concern in humid environments.
Stonebrood gets its name from the characteristic hardness of infected larvae. Unlike chalkbrood mummies, which are chalky and crumbly, stonebrood mummies are rock-hard due to the dense fungal mycelium that completely colonizes the larval tissue. They may also appear yellow-green, brown, or black depending on the Aspergillus species involved.
The disease is diagnosed by the distinctive hardness of the dead larvae and, in advanced cases, visible fungal growth (powdery spore masses) on the surface of dead larvae or around comb cells. A diagnostic confirmation requires microscopic examination of the fungal spores by a laboratory.
Stonebrood is relatively rare and usually self-limiting. It tends to appear in colonies kept in poorly ventilated, damp conditions. Improving hive ventilation, ensuring good drainage at the hive site, and maintaining strong colonies with good hygienic behavior are the primary management strategies.
There are no approved chemical treatments for stonebrood. Heavily infected frames should be removed and replaced. If persistent, requeening with hygienic stock may help, as hygienic bees detect and remove diseased larvae before the fungus can complete its life cycle.
Aspergillus species can cause respiratory infection (aspergillosis) in immunocompromised individuals. When handling stonebrood-affected frames, avoid inhaling spores by wearing a dust mask. For healthy individuals, the risk is minimal, but reasonable precautions are warranted.
Both are fungal brood diseases, but they are caused by different fungi and have distinct symptoms. Chalkbrood mummies are soft, chalky, and white to gray. Stonebrood mummies are rock-hard and may be yellow-green to black. Stonebrood is considerably rarer than chalkbrood.
No. Unlike American foulbrood, stonebrood does not require hive destruction. The fungal spores do not persist as tenaciously, and the disease is usually manageable through improved ventilation, frame replacement, and requeening if necessary.
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