Abstract

The pathogenic organism of aggregate sheath spot of rice in California is Rhizoctonia oryzae-sativae, a binucleate Rhizoctonia sp. The disease's recent rise in occurrence and severity has coincided with a rise in producers' usage of semidwarf varieties. The disease has symptoms that are extremely similar to rice sheath blight caused by R. In the southern United States, there is a place called solani. The fungus isn't doing well.During the tillering stage, aggregate sheath spot lesions first occur on the lower leaf sheaths at the water line. Lesions range in size from round to elliptical in shape, with gray-green to straw-colored centres and noticeable brown edges. Additional margins frequently grow around the original lesion, resulting in a series of concentric bands. The lesion's centre has a strip of light-colored necrotic cells running down it.