DISEASES OF CORN - NORTHERN CORN LEAF BLIGHT

Northern corn leaf blight (NCLB) is caused by the fungus Exserohilum turcicum which overwinters in infested corn debris in warm climates. The fungus is not believed to survive harsh Wisconsin winters. Under suitable weather conditions (moderate temperatures and high humidity) the fungus produces spores that easily become air-borne and can be carried for miles. These spores initially infect lower corn leaves and lead to the development of large, gray-green to tan, spindle-shaped lesions. These lesions may eventually coalesce (merge) leading to death of large portions of a leaf or even entire leaves. Additional spores are produced in leaf lesions, leading to infection of upper leaves. Severe infections prior to silking can lead to substantial yield losses. Infections after silking tend to be less detrimental and lead to less substantial yield losses.

The primary method of disease control for NCLB is through use of resistant corn varieties. For high value corn crops such as seed corn, fungicide treatments are available and may be economically feasible. In Wisconsin, crop rotation and management of corn debris are not useful management techniques, because spores that produce initial infections originate in warmer climates and are blown into local cornfields.