Blackish areas on tuber are sclerotia - Claflin, Larry (My University, 1977)
The "dirt-like" blackish areas on the tuber are sclerotia, the resting stage of rhizoctonia solani.
Host/Plant: Potato (Solanum tuberosum subsp. tuberosum)
Pest/Path: Rhizoctonia Canker and Black Scurf (Rhizoctonia solani)
Keywords: Fungal Diseases; Potato Diseases; Rhizoctonia; Color photographs