Do you recognise this brood disease? Explain what you see.
- Banded brood associated with wax moth.
- American foulbrood, a bacterial brood disease.
- Healthy colony with regular brood.
- Chalkbrood, a fungal brood disease.
- Deformed Wing Virus: DWV, a viral disease.
- European foulbrood, a bacterial brood disease.
- Nosemosis affecting mainly adult bees.
Show answer
Correct answer: 6.
Probably European foulbrood, a bacterial brood disease.
Why?
European foulbrood is a bacterial brood disease caused by Melissococcus plutonius. It mainly affects the young larvae, often before capping.
In the expected image, the suggestive signs are patchy brood, flaccid larvae turning yellowish to brownish, and diseased or dead larvae placed in abnormal positions in the cells.
The word 'probably' is important here: irregular brood or abnormal larvae can point towards European foulbrood, but an image is not always enough to decide with certainty.
What to understand
European foulbrood can remain barely visible as long as the bees quickly remove the affected larvae. The symptoms become clearer when infection pressure increases or when cleaning behaviour is no longer sufficient.
It can be confused with other brood disorders, notably American foulbrood, chalkbrood, or non-infectious damage. The ropiness test can help: in European foulbrood, the mass is often viscous, but little or not stringy, generally less than 1 cm.
In Switzerland, a suspicion of European foulbrood must be taken seriously. Handling should be limited, no suspect combs, colonies, or equipment should be moved, and the apiary inspector should be contacted.
Key takeaways
The important signs are patchy brood, flaccid larvae that are yellowish to brownish, abnormal larval positions, and sometimes a sour or unpleasant odour.
An image can guide the diagnosis, but it does not replace the health assessment of a suspect colony.
The right reflex is to move nothing and to quickly seek competent advice in case of doubt.
Further reading
► Practical Guide: 2.2 European foulbrood
► Practical Guide: 2 Diseases and pests