DISEASES OF CORN - ANTHRACNOSE STALK ROT

In general, severe leaf disease predisposes corn plants to stalk rots. Loss of leaf area forces plants to increasingly rely on stalks for nutrients as ears fill and mature, thus robbing materials that would normally be used to strengthen the stalk and potentially ward off infections. In the case of anthracnose, the pathogen has an even more direct effect. Colletotrichum graminicola can infect not only corn leaves, but can also directly infect the stalk and cause decay.

Anthracnose stalk rot is a common stalk rot found in Wisconsin. Corn stalks affected by anthracnose stalk rot are characterized by having shiny black, blotchy areas on their surfaces. The shiny aspect of the diseased areas is diagnostic. Internally, stalks with Anthracnose stalk rot exhibit a tan to black discoloration and disintegration of the pith tissue.

Anthracnose stalk rot can often be controlled through use of resistant varieties. Also, elimination of corn debris by deep plowing can be beneficial, although some research suggests that the fungus can survive several years associated with buried debris. Cultural practices such as production of continuous corn or use of no-till practices tend to favor the development of the disease. Also, a high soil N/K ratio tends to favor disease development. Thus proper soil fertility is critical in the management of this disease.