Do you recognise this brood disease? Explain what you see.
- Banded brood associated with wax moth.
- American foulbrood, a bacterial brood disease.
- Chalkbrood, a fungal brood disease.
- European foulbrood, a bacterial brood disease.
- Healthy colony with regular brood.
- Deformed Wing Virus: DWV, a viral disease.
- Nosemosis affecting mainly adult bees.
Show answer
Correct answer: 4.
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 ropiness test may show a viscous mass, but one that is little or not stringy, generally less than 1 cm. A sour or unpleasant odour may be present, but on its own it is not enough to make the diagnosis.
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.
Differential diagnosis is essential. Patchy brood or dead larvae are not enough on their own: European foulbrood must be distinguished from American foulbrood, from chalkbrood, and from other brood disorders.
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 quickly.
Key takeaways
The important signs are patchy brood, flaccid larvae that are yellowish to brownish, abnormal larval positions, and a mass that is little stringy in the ropiness test.
Adult bees can contribute to the spread of the pathogen, even though the visible symptoms mainly concern the brood.
The right response is to move nothing, to limit handling, and to quickly seek competent advice.
Further reading
► Practical Guide: 2.2 European foulbrood
► Practical Guide: 2 Diseases and pests