Anthracnose leaf blight of corn
Anthracnose leaf blight is caused by the fungal pathogen Colletotrichum graminicola and seldom causes yield loss. Early in the season, lower leaves usually show symptoms first. Later, symptoms can occasionally be found on upper leaves. Leaf lesions are oval or spindle shaped, tan or brown with dark brown or purple margins, up to 1 inch long and ½ inch wide. As the disease develops, the fungus produces black, spiny fruiting structures on the dead leaf tissue. These are visible with a 30X hand lens. On severely infected leaves, the lesions can grow together into large dead areas. These leaves may turn yellow and wither.
The fungus overwinters as mycelium or sclerotia in corn residue or seed. Spores are spread primarily by splashing water. Disease development is favored by wet weather during early crop growth with moderately warm temperatures. Anthracnose leaf blight is most common where corn follows corn. Disease develops soon after planting and continues to develop until canopy closure.
Resistant hybrids and inbreds are available. Crop rotation and tillage reduce survival of the fungus and foliar fungicides labeled for anthracnose leaf blight are available.
Gallery Images: G. Munkvold, D. Mueller, A. Robertson, and C. Grau