Black dot

Colletotrichum coccodes

Symptoms

• Grey-brown spots resembling silver scurf (slightly greyer and less sharply outlined than silver scurf)
• In the grey-brown spots small black dots are visible (these are more widely spaced than in silver scurf)
• Advanced infection shows sunken, black spots on the skin
• After foliar desiccation, black dot can occur on the stems and roots
• Often a part of the stolon remains attached to the tuber
• Symptoms of stem end necrosis/stem end rot with black microsclerotia

Spread

• Predominantly via the soil
• Also via seed tubers
• Spread during storage in humid conditions

Possible confusion with

• Silver scurf (Helminthosporium solani)