Sheath Blight

Sheath Blight:Rhizoctonia solani


  • The fungus affects the crop from tillering to heading stage.
  • Initial symptoms are noticed on leaf sheaths near water level.
  • On the leaf sheath oval or elliptical or irregular greenish grey spots are formed.
  • As the spots enlarge, the centre becomes greyish white with an irregular blackish brown or purple-brown border.
  • Lesions on the upper parts of plants extend rapidly coalescing with each other to cover entire tillers from the water line to the flag leaf.
  • The presence of several large lesions on a leaf sheath usually causes the death of the whole leaf, and in severe cases, all the leaves of a plant may be blighted in this way.
  • The infection extends to the inner sheaths resulting in the death of the entire plant.
  • Older plants are highly susceptible.
  • Five to six-week-old leaf sheaths are highly susceptible.
  • Plants heavily infected in the early heading and grain filling growth stages produce poorly filled grain, especially in the lower part of the panicle.
  • A yield loss of 25% was reported if the flag leaves are infected.

Mode of Spread and Survival: 

  • The pathogen can survive as sclerotia or mycelium in dry soil for about 20 months but for 5-8 months in moist soil.

Favourable conditions:

    • Presence of sclerotia or infection bodies floating on the water
    • Presence of the sclerotia in the soil
    • Relative humidity from 96 to 100%
    • Temperature from 28-32 °c
    • High levels of nitrogen fertilizer
    • High seeding rate or closing plant spacing
    • Frequent rain

Identification of pathogen:

  • The disease is soil-borne
  • The fungus produces usually long cells of septate mycelium which are hyaline when young, yellowish brown when old.
  • It produces a large number of globose sclerotia, which are initially white, later turn to brown or purplish brown.
  • There are three types of mycelium produced: runner hyphae, lobate hyphae and monilioid cells.
  • Sclerotia consist of compact masses of mycelia. They are irregular, hemispherical, flattened at the bottom, white when young and turn brown or dark brown when older. Individual sclerotia are 1-6 mm in diameter. They may unite to form a larger mass. Large sclerotia are significantly more virulent than smaller ones.


Cultural methods

  • Apply FYM 12.5 t/ha or green manure 6.25 t/ha to promote antagonistic microflora
  • Avoid excess doses of fertilizers.
  • Adopt optimum spacing.
  • Eliminate weed hosts.
  • Apply organic amendments.
  • Avoid flow of irrigation water from infected fields to healthy fields.
  • Deep ploughing in summer and burning of stubbles.

Chemical methods:

  • Apply Neem cake at 150 kg/ha
  • Foliar spray with Neem oil at 3% (15 lit /ha) starting from disease appearance.
  • Soil application of P. fluorescens talc based formulation at 30 DAT @ 2.5 Kg/ha and foliar spray (0.2%) at boot leaf and 10 days later @ 1 Kg/ha.
  • Seed Treatment with TNAU Pf 1liquid formulation @ 10 ml/kg of seeds
  • Seedling root dipping with TNAU Pf 1liquid formulation (500 ml for one-hectare seedlings)
  • Foliar spray with TNAU Pf 1liquid formulation @ 5ml/lit
  • Control of sheath blight has been mainly through the use of foliar fungicides.
  • Spraying of Carbendazim 50 WP @ 500g/ha or Azoxystrobin @ 500ml/ha or
  • Hexaconazole 75% WG @ 100mg/ lit 1st spray at the time of disease appearance and 2nd spray 15 days later (or)
  • Spraying of infected plants with fungicides, such as Benomyl or Iprodione or antibiotics, such as Validamycin and Polyoxin is effective against the disease



  • TamilNadu Agritech Portal
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