Do you recognise this brood disease? Explain what you see.
- Chalkbrood, a fungal brood disease.
- European foulbrood, a bacterial brood disease.
- Healthy colony with regular brood.
- American foulbrood, a bacterial brood disease.
- Banded brood associated with wax moth.
- Deformed Wing Virus: DWV, a viral disease.
- Nosemosis affecting mainly adult bees.
Show answer
Correct answer: 4.
American foulbrood, a bacterial brood disease.
Why?
American foulbrood is a highly contagious bacterial brood disease, caused by Paenibacillus larvae. It affects bee larvae and often becomes visible in the capped brood.
In the expected image, the suggestive signs are patchy brood, cappings that are dark, flattened, sunken, or perforated, as well as capped cells from which the bees do not emerge normally.
The ropiness test may show a brownish larval mass that forms a thread. At an advanced stage, one may also observe dark brown to black scales, flat, tongue-shaped, and strongly adherent in the cells.
What to understand
American foulbrood can remain barely visible at first, especially if the colony still removes some of the affected larvae. By the time the symptoms become obvious, the disease may already be well established.
The distinction from European foulbrood is important. In American foulbrood, the larvae often die after capping, the mass is generally more stringy, and the scales remain strongly stuck to the cell.
In Switzerland, American foulbrood is a notifiable disease. In case of suspicion, handling should be limited, no combs, colonies, or equipment should be moved, and the apiary inspector should be contacted quickly.
Key takeaways
The warning signs are patchy brood, dark, perforated, or sunken cappings, a stringy larval mass, and dark, adherent scales.
American foulbrood is a serious brood disease. It must not be managed alone at the apiary.
The right response is to move nothing, to limit handling, and to quickly seek competent advice.
Further reading
► Practical Guide: 2.1 American foulbrood
► Practical Guide: 2 Diseases and pests