Rice sheath blight early symptoms usually develop on leaf sheaths at or just above the water line as circular, oval, or ellipsoid, water-soaked spots that are greenish-gray in color. As the disease progresses, they enlarge and tend to coalesce forming larger lesions with grayish-white centers surrounded by tan to dark brown irregular borders or outlines. Infection can spread to leaf blades and cause irregular lesions with dark green, brown, or yellow-orange margins. The lesions can develop extensively and coalesce on partial or whole leaf blades, which may produce a rattlesnake skin pattern. These damaged tissues interrupt the normal flow of water and nutrients to the plant tissues above (leaves and panicles). As the plant approaches the heading, the canopy becomes dense, creating a humid microclimate that is favorable for the rapid development of the disease. The disease may move up the plant and infect the flag leaves and panicles under severe conditions. The fungus can spread into the culms from early sheath infections and weaken the infected culms, resulting in the lodging and collapse of tillers. The damage caused by sheath blight ranges from partial infection of the lower sheaths with little impact on grain filling to the premature death of plants and lodging with a significant reduction in grain yield and quality.