Pathogen(s) causing disease: Colletotrichum graminicola
Location: Predominantly in the US, Europe and Southeast Asia
Symptoms: Anthracnose of corn may appear as a leaf blight, stalk-rot, top-kill of the
stalk, and kernel rot. But most damage results from the stalk rot and leaf blight phases. Lesions can be found on leaves of very young plants soon after emergence. Leaf lesions are generally brown, oval to spindle shaped, about 1/4 inch wide by 1/2 inch long. Usually, a yellow or yellow-orange area surrounds the disease portion of the leaf. Lesions vary greatly among different hybrids making diagnosis in the field very difficult. The fungus can usually be seen on the leaf surface with the aid of a hand lens.
Conditions: Favored by cool to warm, wet, humid weather, continuous corn with reduced tillage.
Management:
Hybrid selection is the first step in disease control. Growers should carefully select hybrids with the proper leaf blight and stalk rot resistance, with good standability, and high yield potential. Resistant varieties are not always available for stalk rot.
Since the anthracnose fungus survives in corn residues, especially on the soil surface, the disease may be more serious under reduced tillage systems and in continuous corn. A tillage system that chops and completely buries the residues coupled with a one-year rotation away from corn will eliminate the local source of inoculum. A two-year rotation away from corn may be necessary under no-tillage or reduced tillage systems.
Avoid excessive plant stress by using a balanced soil fertility program based on soil tests. Plant at populations suggested for the particular hybrid, and control insects such as the European corn borer and corn rootworm.
Sources:
Purdue University
The Ohio State University
Bloomberg, Jim. Bayer CropScience Corn Disease Identification Guide PowerPoint. 2009.
