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Northern Leaf Spot

© Purdue University, Plant and Pest Diagnostic Laboratory

Pathogen(s) causing disease:

Helminthosporium carbonum (Race 3)


Narrow, small, linear to oval shaped leaf lesions Race 1 lesions are tan, oval to circular with concentric zones and are commonly 1/2 inch in width and 1 inch in length. Race 2 infections are rare. Lesions are oblong, dark brown to blackish in color and 1/8 inch in width and 1 inch in length. Race 3 lesions are most common in the Corn Belt. These lesions are narrow and linear in shape, with lengths less than 1 inch and widths less than 1/8 inch. Lesion shape and size may vary with the genotype of the plant. Chain-like leaf lesions are often produced.


Favored by moderate temperatures and high relative humidity, minimum tillage, continuous corn.


Resistant hybrids. Disease is primarily a problem in seed production fields with certain highly susceptible inbreds. Foliar fungicides may be useful in seed production fields. Cleanly plow under infected residue.


Purdue University
University of Illinois

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