- The disease is caused by Clavibacter michiganensis subsp. sepedonicus.
- This is a quarantine disease.
- Tuber symptoms
- a soft cheese-like rotting of the vascular ring, particularly at the stem end
- a cheese-like ooze from the vascular ring if a cut tuber is squeezed
- the bacterial ooze is odourless and unlike brown rot does not stream from infected tissues when held in water
- in severe cased the tuber skin may crack
- Foliar symptoms
- these may be seen late in the season as yellowing and wilting of leaves and stems, particularly if soil is dry and air temperatures are high
- cool, moist conditions are likely to prevent expression of foliar symptoms
- Progeny tubers become infected via stolons of the parent plant and tubers can also become infected through wounds at harvest.
- The bacterium can survive in volunteer potatoes and on boxes, machinery, etc which have been in contact with the bacterial ooze.
- The disease is favoured by cool climates and could survive in soil in association with volunteer potatoes.
- The only control is through use of disease-free seed.
- Seed tubers from UK certified Safe Havens are grown from brown rot free sources and to a very high standard of hygiene.
- The bacterium is a quarantine organism and an EU Directive requires member states to perform annual surveys for the disease.
- However, sampling may not be adequate to identify all seed lots at risk of carrying the disease.
Bacterial ring rot notes
Ring rot 2004 (Symptoms; biology; control)