The fungus attacks the rice plant at any stage of growth. The disease can cause a seedling blight if the planted seed are infested with the fungus and the seed are untreated.
Young spots are dark brown or purplish brown, older spots are brown with grey or whitish centers.
Spots may be much larger on susceptible varieties. The fungus overwinters in infected plant parts. Primary infection through diseased seed is common. However the spores of the fungus can infect leaves and seed. N increases disease.