The abnormally cool, wet spring has delayed planting across Kentucky. Although farmers are understandably eager to begin planting corn, planting into cool, wet soils can increase the risk of seedling blight.
Seedling blights are caused by several soil- or seed-inhabiting fungi or fungus-like organisms that are prevalent when cool, wet soil conditions persist during and after planting. Cool, wet soils also slow plant growth and development and give pathogens more time to infect and damage seedlings. Two of the most common seedling blights of corn are caused by Pythium and Fusarium species, but other fungi can occasionally cause seed and seedling issues.
Symptoms of seedling blights can be observed after emergence and in the early vegetative stages of growth. Farmers should look for areas in the field with poor emergence, patchy stands, and/or stunted plants (Figure 1). Often these symptoms are observed first in poorly drained or ponded areas of the field, and areas with heavy or compacted soils. Infected seeds may rot after germination, preventing emergence and leading to the patchy appearance of plants in a field. Infected plants that do emerge may be yellow, stunted, and have discolored roots. In severe cases, large areas of plants may die leading to reduced stand (Figure 2). It is very difficult to accurately determine the specific organism responsible for a suspected seedling disease issue in the field. Submitting samples through a county Extension agent for submission to the University of Kentucky Plant Disease Diagnostic Laboratory can help with obtaining an accurate diagnosis.
The risk of corn seedling blights decreases when corn is planted into dry soils with soil temperatures above 50˚ F. These conditions allow seeds and seedlings to germinate and emerge rapidly. However, it is often necessary to plant into less-than-ideal soil conditions, and standard corn fungicide seed treatments provide a short window of protection against seedling blights.
By Kiersten Wise, Extension Plant Pathologist