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Skin Spot

Polyscytalum pustulans






Tubers are covered by numerous raised spots surrounded by dark, sunken rings. Damaged eyes show no sign of growth.


The initial sources of infection are seed tubers, which lead to a build-up of inoculum in the soil. Tubers are infected usually through injuries or the eyes during harvest, but the spots are not usually seen until December. Can survive for up to 4 years in the soil or for up to 8 years on plant debris.

Favourable Factors

Wet conditions at lifting and cold conditions early in storage. The use of sprout suppressants may increase the severity of the disease.


The appearance of infected tubers is spoilt and spots in the eyes can cause uneven emergence, blanking (rotting or failure of the seed tuber) or even crop failure.


Identification and Management of potato diseases

Find out more information on the key disease threats to your potato crop. For each disease you will find out the importance of the disease in terms of potential yield penalty, how to identify the disease in its early stages and our advice on the best control strategies.

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