Do you recognise this brood disease? Explain what you see.
- Banded brood associated with wax moth.
- Healthy colony with regular brood.
- European foulbrood, a bacterial brood disease.
- Chalkbrood, a fungal brood disease.
- American foulbrood, a bacterial brood disease.
- Deformed Wing Virus: DWV.
- Nosemosis affecting mainly adult bees.
Show answer
Correct answer: 3.
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 over less than 1 cm. A sour, acidic, or unpleasant odour may also be present, without being enough on its own to establish the diagnosis.
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.
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 reported quickly to the apiary inspector. Before competent advice, moving suspect combs, colonies, or equipment must be avoided.
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 limit handling, move nothing, and quickly seek competent advice.
Further reading
► Practical Guide: 2.2 European foulbrood
► Practical Guide: 2 Diseases and pests