Caused by a common bacterium that persists in soil and water, and spread by wind-driven rains. Bacterial leaf blight develops on upper leaves of wheat during periods of wet weather, high humidity and air temperatures of 60-78 F after plants have reached the boot stage. Initial lesions appear as small water-soaked spots. Lesions expand and become necrotic. Spots often coalesce in a few days to form large blotches. Entire area of an infected leaf may be affected. Head tissue usually does not develop symptoms. Bacteria leaf blight can also attack corn and grain sorghum.