Eyespot of corn
Eyespot is caused by the fungus Aureobasidium zeae. The initial symptoms of eyespot are small, water-soaked or chlorotic circular spots. The tissue at the center of the spot later dies and turns tan-colored with a brown ring at the margin. The spot is surrounded by a yellow "halo" that can be seen clearly when the leaf is lighted from behind. Spots may join together into large necrotic areas and the entire leaf may die. The spots remain visible even after the leaf dies.
The disease is more common when corn follows corn. Cool temperatures (60s°F to low 70s°F) favor disease development; thus, eyespot may appear early in the season on lower leaves and again near the end of the season on upper leaves. Eyespot lesions on corn leaf. Image: A. Robertson
Backlit eyespot lesions showing yellow "halo." Image: A. Sisson
Resistant hybrids and inbreds are available. Crop rotation and tillage reduce survival of the fungus. Foliar fungicides labeled for eyespot are available.