Figure 2. Seedling blight is generally more severe under cold, wet, soil conditions. Affected plants are usually stunted with yellow or brown leaf tips. Plants die if the fungi attack the crown and growing point. Most affected plants do not fully recover even with improved weather conditions.
Treating corn seed with a fungicide is a highly effective means of preventing or reducing seed decay and seedling blight diseases (Figure 2). These diseases are caused by fungi that reside in or on the seed or in the soil. Seed treatment is especially important when the corn is planted early. Research trials in several Corn Belt states have shown an average yield loss of 10 percent when untreated seed has been planted in cold, wet soils. These conditions favor seedling diseases that cause loss of stands or reduce the vigor of young seedlings. Seed and seedlings are more vulnerable to infection when the soil is cold, but early planting usually is desirable because it generally results in a higher yield. In most cases, seeds treated with fungicides will germinate and begin to grow once the soil warms to temperatures above 50°F. Corn will grow slowly anytime the soil temperatures are below 60°F, and seedling diseases are most prevalent during this time. Kernels that have been cracked or damaged during harvesting or handling are more susceptible to seed rot diseases and must be removed from the seed lot prior to treating the seed with a fungicide. Most seed corn is treated with a fungicide or fungicide-insecticide combination by the seed producer or seed processor. If not, several planter box seed treatment materials are available. Captan, metalaxyl, mefenoxam, and fludioxonil are the fungicides most commonly used on corn seed, but other materials are available. Obtain a copy of Ohio State University Extension Bulletin 639A, Seed Treatment for Agronomic Crops, at http://ohioline.osu.edu/b639/index.html or http://www.oardc.ohio-state.edu/ohiofieldcropdisease/ for a more complete listing of registered materials. Seed treatment is one of the best ways to ensure a good stand, and all corn seed should be treated.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension
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