Sheath blight:

Causal organism: Rhizoctonia sohani (Thanatephorus cucumeris)

• High humid and warm temperature favours the disease.
• Close planting and heavy fertilization tend to increase the incidence of the disease.
• The number of sclerotia in contact with plants is the cause of primary infection.

                                                          

Symptoms:

• Spots or lesions occur mostly on leaf sheath.
• Spots first appear near the waterline in fields. They are greenish grey, elliptical or oval and about 1 cm long and become grayish white with brown margins.
• Under humid conditions, the mycelium of the fungus may grow upward to infect other leaf sheaths and leaf blades touching each other.
• In severe infections, all leaves of a plant may be blighted.

Management:

• Reduce nitrogen and spacing.
• Grow tolerant varieties - Krishna, CR 44-11, Saket-1, Pankaj, T 141, Ptb 21, Swarnadhan