• Black spot (2-3mm in dia) develops around the lenticels which appears as whitish specks at the centre
• On cutting - internal tissues shows black patches beneath the spots on the surface of the tuber

Identification of pathogen:

• Mycelium - sparse or fluffy
• Hyphae - branched, septate and greyish white or brown
• Sclerotia - minute, black and smooth
• Conidiophores - simple and rod shaped
• Conidia - one celled, hyaline, oval or elliptical

Mode of spread and survival:

• Pathogen present in the soil - primary source of inoculum
• Entry of fungus - bruising of skin, insect damage
• Sclerotia – survive in the soil for more than 3 yrs

Epidemiology:

• Disease is more severe in wet soil
• Temp - 31°C

Management: S

• Avoid bruising of tubers during harvest, collection and storage
• Temp of store house should be low
• Early maturing varieties - Kufri Chandramukhi, Kufri Alankar

Source of Images:
http://www.sciencephoto.com/media/132767/view