Early blight of Potato

Early blight of potato: Alternaria solani

  • It is present in both hills & plains.
  • Brown-black necrotic spot-angular, an oval shape characterized by concentric rings.
  • Several spot coalesce & spread all over the leaf.
  • Shot holes on fruits.
Identification of pathogen:
Mode of spread and survival:
  • The conidia and the mycelium in the soil or in the debris of the affected plants can remain viable for more than 17 months.
  • These conidia or the new conidia found on the overwintered mycelium bring about the primary infection of the succeeding potato crop.
  • Secondary infection is more important in the spread of the disease.
  • The conidia formed on the spots developed due to primary infection are disseminated by wind too long distances.
  • The conidia from the affected plant may also be disseminated to the adjoining plants by rain and insects.
  • Dry warm weather with intermittent rain.
  • Poor vigor. Temperature: 25-30°C.
  • Poorly manured crop.
  • Disease free seed tubers should be used for planting.
  • Removal and destruction of infected plant debris should be done because the spores lying in the soil are the primary source of infection.
  • Very early spraying with Zineb or captan 0.2% and repeating it for every 15 – 20 days gives effective control.
  • The variety Kufri Sindhuri possesses a fair degree of resistance.



  • TamilNadu Agritech Portal
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