Eye Spot (Corn)

Kabatiella zeae

Corn leaf infected with eye spot throughout
Corn leaf infected with eye spot throughout. Photo courtesy of Daren Mueller. Licensed under CC BY 3.0.
Eyespot is a fungal disease most common throughout the northern midwest, borne through corn residue. It is known to cause significant yield loss in susceptible hybrids.
Eyespot is cause by a fungus that inhabits corn residue and can be very dangerous in no-till or continuous corn fields. It prefers humid and wet conditions. Infection usually sets in between silking and maturity stages. There must be water present on the leave or leaf sheath for the fungus to break out. Symptoms will appear 9 to 10 days after infection.
No-Till Cornfield
No-till cornfields are more susceptible to eyespot infection. Photo courtesy of NRCS. Licensed under CC BY 2.0.
Initial symptoms are small, water-soaked lesions that are circular with yellow halos. As the interior of the lesion dies, it becomes tan in the center with a purple to brown outside ring. Most remain encircled by the remaining yellow halo. If the spots join together, they can form large, necrotic areas. Lesions may also appear on leaf sheaths and stalks. It's important to not confuse this disease with physiological or genetic leaf spots, which have no negative effects on the plant.
Under conditions that involve no-till or consecutive corn planting years, the disease can result in yield loss. If plants are infected early on in life can cause barrenness. More mature plants that are infected will lose valuable photosynthetic area and results in overall yield reduction.
Consistent tillage will help reduce the fungal presence, but the most effective method for control is to rotate away from corn each year. One year will allow the corn residue to decay to a point where fungus levels will not be an issue.
Fungicide application can be effective if used early on in an epidemic, especially in seed corn that in a reduced tillage field. It's only recommended if the previous year had eyespot infections, but always consider resistant hybrids as the number one option. Please contact your local plant pathologist to learn what is most effective in your area and how to use it best. Always read and follow all label instructions.
Plant corn hybrids that have at least some resistance to eyespot. There are available varieties.