Black scurf Potato

Black scurf: Rhizoctonia solani


  • Black speck, black speck scab, russet scab on tubers.
  • At the time of sprouting dark brown colour appears 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 a source of spread. Moderately cool, wet weather and temp 23 °C are the favourites for the development of the 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 the 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 tubers may be planted shallow to control the disease.
  • The disease severity is reduced in the land is left fallow for 2 years.
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