Anthracnose stalk rot of corn
Anthracnose is likely the most prevalent stalk rot in the eastern United States. Affected plants have shredded pith and die prematurely. Anthracnose also causes a distinctive blackening of the stalk rind. Initially, these areas are narrow, water-soaked lesions, but they turn very dark and shiny and can join together to form large black blotches or streaks over the growing season. Anthracnose also can cause a top dieback, where the stalk above the ear dies four to six weeks after pollination.
The fungus overwinters in corn residue and infects plants through the roots or by spores that splash onto the stalk or are carried by insects that may introduce them into feeding wounds. Seedlings can be infected, and some plants may die before pollination. The disease usually does not appear until late in the season and occurs more severely where corn follows corn, especially in reduced tillage.
Resistance to anthracnose is available in some hybrids. If a hybrid is resistant to stalk rot, it is not necessarily resistant to the leaf blight phase. Rotation and tillage will reduce inoculum. If more than 10 to 15 percent of stalks are observed to be rotted 40 to 60 days after pollination, the field should be scheduled for earliest possible harvest.
Gallery Images: A. Robertson, G. Munkvold, C. Grau, and A. Sisson