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Symptoms of Sheath Blight of Rice:
1. The fungus affects the crop from tillering to heading stage. Initial symptoms are noticed on leaf sheaths near water level.
2. 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.
3. Lesions on the upper parts of plants extend rapidly coalesing with each other to cover entire tillers from the water line to the flag leaf.
4. The presence of several large lesions on a leaf sheath usually causes death of the whole leaf, and in severe cases all the leaves of a plant may be blighted in this way.
5. The infection extends to the inner sheaths resulting in death of the entire plant. Older plants are highly susceptible.
6. 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.
C S Azad University of Agriculture and Technology, Kanpur