• Black speck, black speck scab, russet scab on tubers.
• At the time of sprouting dark brown colour appear on the eyes.
• Affected Xylem tissue causes to wilting of plants.
• Infected tuber contains russeting of the skin.
• Hard dry rot with browning on internal tissue.
• Seed tubers are source of spread. Moderately cool, wet weather and temp 23 °C are the favourable for the development of disease.

Identification of pathogen:

Mode of spread and survival:

• The sclerotia on the seed tubers is the principal source of infection of the subsequent crop raised with these tubers.
• On return of favourable conditions the mycelium present in the soil may develop producing new hypae.

• Disease free seed tubers alone should be planted.
• If there is a slight infection of black scurf that can be controlled by treating seed tubers with mercuric chloride solution for 1.5 hr with acidulated mercuric chloride solution for 5 min.
• Treating the soil with pentachloroni trobenzene at the rate of 70 kg/ ha lowers the incidence of the disease, but it is too expensive and cumbersome.
• Well sporulated tubrs may be planted shallow to control disease.
• The disease severity is reduced in the land is left fallow for 2 years.