Black scurf

Description

The fungus forms dark brown to black hard masses on the surface of the tuber. These are called sclerotia and are resting bodies of the fungus. Sclerotia are superficial and irregularly shaped, ranging from small, flat, barely visible blotches to large, raised lumps. Although these structures adhere tightly to the tuber skin, they do not penetrate or damage the tuber, even in storage. However, they will perpetuate the disease and inhibit the establishment of potato plants if infected tubers are used as seed.