Corn Leaf Blight

Northern corn leaf blight (NCLB) is caused by the fungus Exserohilum turcicum; Southern corn leaf blight (SCLB) is caused by Cochliobolus heterostrophus

Southern corn leaf blight
Southern corn leaf blight [Credit: David B. Langston]


Host Plants:

On Crops: All types of sweetcorn and maize

Where Found:

Worldwide, wherever sweetcorn or maize is grown in temperate climates

Description:

Northern sweetcorn leaf blight causes large spots to form on sweetcorn leaves, which begin as grey-green areas several inches long and one-half inch wide. The spots quickly turn to tan. A disease of wet weather, northern corn leaf blight is most severe when temperatures are between 18-27C (66-80F), with constant moisture from rain or fog. The leaf spots caused by Southern corn leaf blight are smaller, usually less than two inches long, and outbreaks are triggered by persistent warm rains, with temperatures between 21-32C (70-90F). The spots become numerous and run together, often causing the whole leaf to wither.

Damage:

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.

Preventing Problems:

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.

Managing Outbreaks:

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.

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