Anthracnose leaf blight
Anthracnose leaf blight can be a problem on susceptible hybrids. Symptoms are occasionally seen on resistant plants and can be confused with other foliar diseases. The causal pathogen of anthracnose leaf blight also produces a stalk rot and top dieback.
The first symptoms of anthracnose leaf blight are water-soaked, oval lesions with tan centers and reddish-brown borders. Symptoms begin on lower corn leaves early in the growing season and then develop on the upper leaves late in the season. Lesions can enlarge up to 5" to 6" long and may join and blight the entire leaf, causing it to die late in the growing season. Dark, raised spots (fruiting bodies) and spines appear on dead tissue. Resistant corn lines may be infected but will only have small, necrotic or chlorotic lesions.
Conditions and Timing that Favor Disease:
The disease favors high temperatures and prolonged wet weather. It is most likely to infect at the seedling phase and at full maturity of corn, but not in the middle of the season.
The pathogen is a fungus called Colletotrichum graminicola. It overwinters in corn debris and is spread by wind and splashing rain.
The best way to reduce anthracnose is to use resistant hybrids. Tillage may be beneficial where appropriate, and crop rotation can reduce early season infection.