The main symptoms are leaf spotting, top die-back and stalk rot and anthracnose can affect both the leaves and stalks.
Leaf spots are oval (up to 15 mm long) with a tan centre and reddish-brown border. Individual lesions may join forming streaking along the margin or mid-rib. A general yellowing of the tissue surrounding the infected areas often develops. With the aid of a handlens, small black spots can be seen in the centre of the lesions. Under close examination, black hairs (setae) may be seen protruding from these spots.
The disease is first observed on the lower leaves especially early in the season and later on the upper leaves. Top die-back can occur late in the season as diseased leaves wilt and gradually die above the ear which resembles frost damage.
Residue is an important component in anthracnose development since the fungus survives (overwinters) as mycelium or sclerotia within corn residue or seed. Rain splashes spores from the corn residues onto the lower leaves and stalk. For this reason, corn fields that follow corn (second year corn) are the most prone to anthracnose infection especially when the weather is warm and wet.
There are differences between seed corn inbreds and field corn hybrids in there susceptiblity to anthracnose leaf blight. Do not confuse resistance to anthracnose stalk rot since this is separate from anthracnose leaf blight. Hybrid resistance to anthracnose stalk rot does not guarantee resistance to anthracnose infections on leaves. In conventional corn fields, removal of corn residues through tillage will lower your risk to the disease especially when corn follows corn. In no-till or reduced tillage fields, management of anthracnose leaf blight is best achieved with rotations (avoiding second year corn) and planting resistant corn hybrids. Fungicides applications are not economical in field corn situations because more than one application is necessary to control the disease, however, in seed corn fields fungicide applications may be cost effective, especially if a very susceptible inbred is planted into a lot of residue.
Source : OMAFRA