Corn Disease Management in Ohio

Bulletin 802

Summary of Management Practices

1. Plant high-quality seed, treated with a seed-protectant fungicide, in a well-prepared seedbed. Sow seed at rates recommended by the seed company to ensure proper plant populations. When populations are too high, the stress caused by plant-to-plant competition may increase stalk rot.
2. Plant high-yielding hybrids with resistance to leaf blight, ear rots, and stalk rots. Several potentially destructive diseases now cause only minor losses due to widespread use of resistant hybrids.
3. Use balanced fertility, which is the key to vigorous, well-developed plants. High rates of nitrogen, especially when excess in relation to potassium, favor the development of stalk rot and some leaf diseases. Use recommended levels of N, P, and K, based on soil tests.
4. Rotate crops and destroy corn residues to effectively reduce the numbers of disease organisms surviving in the field. However, to conserve energy and to protect soil from loss through erosion, reduced tillage practices are being used increasingly. As a result, these disease-control practices are lost. Other disease management practices, such as use of resistant hybrids and longer crop rotation, become essential to make up for this loss.
5. Improve soil drainage in poorly drained soils. This reduces water stress and reduces losses from seedling blights, root rots, and stalk rots.
6. Control insects and weeds in and around fields. Insects such as root worm and stalk borer create wounds that serve as entry points for disease-causing fungi. Additionally, the corn flea beetle carries and spreads the bacterium causing Stewart’s bacterial leaf blight. Some weeds act as reservoirs for overwintering of corn pathogens. In southern Ohio, eradicate johnsongrass to control viral diseases.
7. Scout fields for leaf blight diseases prior to and two weeks after tasseling. Fungicide application may be justified only if very susceptible hybrids or inbreds are used and the lower leaves are infected before or very soon after tasseling.
8. Survey fields 10 days to two weeks prior to harvest to determine the incidence of stalk rot. A rapid and easy technique to determine the incidence of stalk rot is the “squeeze” method. Grasp the base of the stalk above the brace roots and squeeze the stalk between the thumb and first two fingers. Stalks with significant rot will crush easily. Those fields with the greatest percentage of rotted stalks should be harvested first to avoid losses due to lodged corn.
9. Adjust and operate the combine or picker properly to reduce harvesting losses in the field with stalk-rotted, lodged corn. Some equipment companies have attachments for the combine header to help pick up lodged corn.
10. Dry shelled corn to 13 percent to 14 percent. Ear corn to be cribbed should be dried to 20 percent moisture. Maintain cool and dry storage conditions to prevent storage molds from developing.

Copyright © 2004, Ohio State University Extension

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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension

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