Although more than 30 different diseases affect corn in Ohio, only about half cause economic losses. Approximately 5 percent to 15 percent of the state’s corn crop is lost to disease each year, which amounts to nearly $100 million in lost farm income. Many factors determine the severity of disease in a particular year or a specific field. Weather affects dissemination of disease agents and rate of disease spread. Crop rotation and tillage practices are important in determining pathogen survival. Plant nutrition strongly influences hybrid susceptibility to certain diseases. Soil type and soil moisture influence many diseases, and hybrid resistance is the single most important factor in the preservation of plant health.
The major diseases affecting corn in Ohio are listed in Table 1. These are leaf blights, stalk rots, ear and kernel rots, seedling diseases, and viral diseases. Some miscellaneous diseases occur, such as common smut and crazy top, but they usually cause little economic loss. Disease can occur on the corn plant during any stage of growth, from germination to maturity. For identification purposes, a 0-to-9 scale has been developed to describe the different growth stages of corn (Figure 1). The cornerstone to successful disease control is correct identification of specific disease problems. Disease samples can be submitted to the Plant and Pest Diagnostic Clinic for diagnosis at the following address:
C. Wayne Ellett Plant and Pest Diagnostic ClinicClinic forms and information on proper packaging of plant materials can be obtained from your county Ohio State University Extension office.
| Table 1. Diseases Affecting Corn in Ohio | |||||
| Leaf Blights | Stalk Rots | Ear and Kernel Rots | Seedling Diseases | Virus | Miscellaneous |
|---|---|---|---|---|---|
|
*Northern corn leaf blight race 0, 1 *Southern corn leaf blight race T, O Northern leaf spot race 1, 2, 3 *Stewart’s bacterial wilt and leaf blight *Anthracnose *Eyespot *Common Rust *Gray leaf spot Yellow leaf blight Holcus spot Bacterial stripe Physoderma brown spot Southern Rust |
*Gibberella *Anthracnose *Fusarium Diplodia Bipolaris Bacterial Nigrospora |
*Gibberella ear rot *Diplodia ear rot *Fusarium kernel rot Nigrospora ear and cob rot Penicillium rot Aspergillus rot |
*Pythium *Fusarium *Gibberella Bipolaris |
*Maize dwarf mosaic *Maize chlorotic dwarf Wheat streak mosaic |
Common smut Crazy top Nematode diseases |
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All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension
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