Affected leaves are covered with numerous small round spots.
Spots are about 1/8 inch in diameter, oval to circular and initially appear water soaked.
The central area of the spot soon dies, leaving a tan center surrounded by a distinct brown to purple border. The border is frequently encircled by a yellow halo.
Facts
Eyespot appears to be most severe in fields where residues from the previous corn crop are left on the soil surface and in fields of continuous corn for 2 or more years.
Eyespot is favored by long periods of cool, wet weather during the growing season and is more of a problem in the northern regions of the Corn Belt.
Life Cycle of Eyespot
The fungus overwinters and survives between corn crops on residue left on the soil surface.
In the spring, the fungus produces spores that are carried to the new corn crop.
The fungus may also be seed-borne, but this source of fungal inoculum is insignificant when compared to the number of spores produced on infested crop residues.
Management of Eyespot
Plant corn hybrids that have some resistance to eyespot.
Crop rotation and clean plow down of corn residues will help reduce the amount of surviving fungus and limit early season disease spread.