Silver scurf

Helminthosporium solani

Symptoms

• Brown/silver grey spots (clearly visible after washing)
• Spots are initially circular, eventually covering the whole tuber
• In humid circumstances, black thread-like conidiophores can occur at the borders of the lesions (hand lens required)
• Eventually tubers shrivel as a result of dehydration
• Reduced vigour of infected seed tubers

Infection and spread

• Spores from infected seed potatoes and groundkeepers spread to daughter tubers. Infection from the soil is negligible
• Contamination occurs during harvesting and storage
• Hot, humid storage increases infection
• No other host plants known

Possible confusion with

• Black dot (Colletotrichum coccodes)