Bacterial Soft rot Potato

Bacterial Soft rot potato: Erwinia carotovora subsp caratovora


  • Infection at two phases is blackleg and soft rot.
  • The black lesion appears on the base of the plant.
  • Systemic and browning of infected tubers.
  • Yellow appearance of the plant.
  • Finally, the plants wilt and die.
  • Rot and collapse of tubers.
  • The soft, reddish or black ring appears on the infected tuber.

Identification of pathogen:

Mode of spread and survival:

  • Infected tubers attract the flies (Hymelia and Phorlin sp).
  • Spread through immature contaminated soil and tuber.
  • Optimum temperature 21 to 29 ºC and RH 94%


  • The pathogen is difficult to control because of long survival both on seed tubers and in soils.
  • However, using disease-free seed tubers could minimize the disease incidence.
  • Before planting the seed tubers are treated with Boric Acid (3% for 30 minutes) and dried in shade.
  • The same treatment is repeated before the storage of the tubers.
  • The disease can be reduced by soil application of PCNB (30 kg/ha) at the time of planting.
  • Following crop rotations with wheat, pea, oats, barley, Lupin, soybean, sorghum and bajra checks the disease development.
  • In plains, treatment of the seed tubers with TBZ + acetic acid + 0.05% Zinc Sulphate solution or Carbendazim 1% for 15 minutes effectively control the disease. Soaking of tubers in Mercuric chloride 0.1% formalin.
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