Corn leaf blight diseases may cause plants to lose their lowest leaves, while the top part of the plant continues to make new growth. However, plants may be weakened and yields may be low when many leaves are lost to leaf blight.
These fungi can overwinter in soil, so always rotate sweetcorn so that it is not grown in the same spot more often than once every three years. Try resistant varieties. Leaves that dry rapidly after rain or heavy dew are unlikely to develop problems with leaf blight, so grow sweetcorn at proper spacing to make sure sunlight reaches all the leaves. Avoid places near trees, fences, or low pockets where dew is heavy and slow to dry.
Clip off affected leaves and dispose of them in an active compost pile. If dry weather returns, infected plants may recover and make a good crop.