Skin spot

Polyscytalum pustulans

Symptoms

• Develops post-harvest
• Small, sunken, dark coloured spots
• Spots may be solitary or in a group
• Initial infection is visible near the stem end and eyes
• There is a cork layer between the healthy and infected plant tissue
• Infected tissue can be easily removed with a knife
• Anti-sprouting products can increase the contamination as no cork layer is formed
• Low temperatures and high relative humidity increase symptoms

Infection and spread

• Seed tubers
• Low temperatures and wet conditions
• Infection starts via lenticels, eyes and mechanical damage