Rice Blast

Symptom

Rice blast was recognized in relation to the rice growth stage affected: seedling blast, leaf blast and and neck and node blast. Seedling blast occurs in seedbeds. Infected leaves have many small, brown, oval leasions. At advanced stages, leaves and leaf sheaths are dead. Severe infections result in the death of large patches of seedlings. In leaf blast, leasions appear on the leaves, particularly near the upper end. Elliptical or spindle-shaped lesions, with pointed ends and grey or white centres; dark-green to reddish-brown margins, sometimes with a yellow halo. In severe infection, lesions coalesce, killing the leaves. Collar blast is commonly found and rotting may result in premature leaf fall. On lower nodes, rotting causes 'white heads'. Neck and node blast occur in nearly mature plants. No grain is formed when these lesions develop early. Later development of leasions results  in the production of poorly developed grain. The seeds may become infected with fungi. The disease also infected on panicle.