DISEASES OF CORN - NORTHERN CORN LEAF SPOT

Northern corn leaf spot (NCLS) is caused by Bipolaris zeicola, a fungus that is closely related to the fungus that causes Northern corn leaf blight (NCLB), Exserohilum turcicum (see below). In Wisconsin, the NCLS fungus survives in corn debris. Fungal spores produced in this debris serve as the primary source of inoculum for infections. Newly infected tissue (lesions) eventually produces spores that can lead to additional infections. Lesions produced by B. zeicola are much smaller than those produced by E. turcicum. They are typically oval and 1/16 to 1/8 wide and up to an inch long. Often lesions are in rows, giving the diseased area a beaded look.

Because the NCLS fungus survives locally in corn debris, crop rotation and clean plowing both impact disease severity and can be effective management strategies. Disease resistant hybrids do exist, but have not been fully exploited. Control of NCLS with fungicides is only economically feasible for high value corn crops such as seed corn.