Early-season corn diseases: Northern Corn Leaf Blight

Early-season infection of northern corn leaf blight on corn leaf in Southwest NY (2019).

Cornell Cooperative Extension’s SWNY Dairy, Livestock and Field Crops Program is working with Cornell University officials to prevent northern corn leaf blight.

In 2019, northern corn leaf blight appeared throughout the Southwest New York region. This year, farmers might be faced with this disease yet again. Normally, northern corn leaf blight is more of an issue in fields that have been planted with corn for more than one year in a row. However, this year has been especially challenging due to the consistent temperatures of 65-85oF, high humidity, and sporadic rainfall. These conditions all contribute to northern corn leaf blight in corn production.

Identifying corn diseases can be difficult. Early northern corn leaf blight symptoms appear as long, narrow, tan lesions that form on the leaf surface of a corn plant. As the disease progresses, the lesions become longer, more oblong or “cigar-shaped” and can appear grayish in color. These lesions can range from one to eight inches long with multiple lesions forming dense, irregular areas of dead tissue on the corn leaves. Once this happens, the plant can no longer develop to its fullest potential, which may reduce crop yields.

Research has shown that there can be a 20% to 50% decrease in corn yields if lesions are present prior to or at tasseling, which is the start of ear development. Fields that have been planted to corn for multiple years in a row are at a much higher risk of northern corn leaf blight because the disease survives the winter on infected corn stubble at the soil surface. As temperatures rise in the spring and early summer, the bacteria that cause northern corn leaf blight can be splashed or wind-blown onto leaves of the new corn crop. Tilling in old corn stalk residue after the corn is harvested, choosing disease-resistant corn hybrids, and strategic use of fungicides are ways to reduce potential yield loss from northern corn leaf blight.

The Southwest NY Diary, Livestock and Field Crops Program is working closely with Cornell University faculty and staff to help producers properly manage this pest. For more information about corn diseases, disease management, or to report a possible case of northern corn leaf blight, contact Josh Putman, field crop specialist, at 490-5572 or jap473@cornell.edu.


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