Do you recognise this brood disease? Explain what you see.
- Banded brood associated with wax moth.
- European foulbrood, a bacterial brood disease.
- American foulbrood, a bacterial brood disease.
- Healthy colony with regular brood.
- Chalkbrood, a fungal brood disease.
- Deformed Wing Virus: DWV.
- Nosemosis affecting mainly adult bees.
Show answer
Correct answer: 2.
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 point towards European foulbrood, but the diagnosis must be confirmed by a competent person when doubt exists.
What to understand
European foulbrood can remain inconspicuous as long as the bees quickly remove the affected larvae. The symptoms become visible when infection pressure increases or when cleaning behaviour is no longer sufficient.
It can be confused with other brood disorders, notably American foulbrood or chalkbrood. 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, European foulbrood is a notifiable disease. In case of suspicion, suspect combs, colonies, or equipment must not be moved before having sought the advice of the apiary inspector.
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 is not always enough to decide between several brood diseases.
The right response is to limit handling, move nothing, and quickly contact the apiary inspectorate in case of doubt.
Further reading
► Practical Guide: 2.2 European foulbrood
► Practical Guide: 2 Diseases and pests