Sclerotium rolfsii

(Stem rot or Southern blight)

• Causal agent and transmission

This soil-borne fungus can attack potato crops and other field and vegetable crops in warm regions. Its presence on potato crops can be seen at the end of the growing season. Coming from soil-borne sclerotia, fan-like mycelium invade stem bases and progress by invading the tubers (photo 1).

Once harvested and stored, the infected tubers show spectacular symptoms of numerous sclerotia bursting out of rotten tubers (photo 2).

• Significance

In the case of severe soil contamination, extensive tuber losses can occur when, during the growing period, the climatic conditions have been favourable to disease development. In such conditions, rotation with non-host crops is advisable.