No. 17/July 16, 1998
Eyespot of Corn
We have received a number of reports concerning the appearance of eyespot of corn. This fungal disease, caused by Kabatiella zeae, is favored by cool and humid weather. It is most common in northern Illinois, although it can occasionally be found in the central parts of the state.
Symptoms of eyespot are primarily very small, circular-to-oval lesions with yellowish "halos" that can fuse to form larger necrotic (dead) areas. This disease is most commonly seen in patches on the leaves and may initially resemble contact herbicide drift. The lesions develop tan- to cream-colored centers surrounded by a brown or purple ring, with a narrow yellow halo, giving the appearance of an "eyespot." Lesions are most common on older plants and are rarely seen during the early part of the season.
The fungus overwinters in corn debris where spores are produced and carried to nearby plants. Lesions take 4 to 10 days to form, depending on weather conditions. Secondary spread is by wind and water splashing of spores from one plant to another.
Control is not usually necessary for eyespot except for seed-production fields. Clean plowing (where possible) and crop rotation help to reduce the incidence and severity of eyespot. Commercial hybrids typically are at least partially resistant, and economic losses to this disease are uncommon.
H. Walker Kirby (firstname.lastname@example.org), Extension Plant Pathology, (217)333-8414