A number of factors may contribute to poor corn stands early in the growing season. Seed decay and seedling blights may certainly cause a rotting or deterioration of ungerminated seed, pre-emergence seedling blight or post-emergence seedling blight. Insect damage, fertilizer or herbicide injury, soil conditions and environmental factors, especially saturated soil conditions and oxygen deprivation may also cause or contribute to early season corn establishment problems. When problems are identified, look for management options that will help avoid similar problems next season.

Soil-inhabiting fungi such as Pythium, Fusarium, Diplodia, Rhizoctonia and Penicillium generally cause seed decay and seedling blights of corn. These fungi may rot the seed prior to germination. Affected seeds are usually discolored and soft and may be overgrown with fungi. Rotted seed may be difficult to find because they decompose very rapidly and because soil adheres fairly tightly to the decomposing seed.

With pre-emergence seedling blights, the seed germinates but the seedlings are killed before they emerge from the soil. The coleoptiles and primary roots are usually discolored and have a wet, rotted appearance. With post-emergence seedling blights, the seedlings emerge through the soil surface before developing symptoms. Seedlings tend to yellow, wilt and die. Discolored, sunken lesions are usually evident on the mesocotyl. Eventually the mesocotyl becomes soft and water soaked. The root system is usually poorly developed, and roots are discolored, water soaked and sloughs off. If the primary root system and mesocotyl are severely affected before the nodal or permanent root system has developed, the plants have little chance of surviving.

Corn seedling blights are more severe in wet soils, in low-lying areas in a field or in soils that have been compacted or remain wet for an extended period of time. Low soil temperatures (50 to 55°F) and wet soil conditions especially favor Pythium seed decay and seedling blight. Disease severity is also affected by planting depth, soil type, seed quality, mechanical injury to seed, soil crusting, herbicide injury or other factors which delay germination and emergence of corn.

Regardless of which pathogen or pathogens are involved, the best way to avoid corn seed decay and seedling blight is to plant high quality seed, which has been treated with a seed treatment fungicide into a good seedbed when soil temperatures are above 50°F. If you plant really early in cold soils, you may have to increase planting rates due to higher germination and seedling emergence mortality. Soil temperatures can change rapidly on sandy soils and dry soils, so watch forecasts and check soil temperatures. A simple thermometer can be used, at a depth of 4 inches at 7:00 a.m. each morning to determine soil temperatures.