The center is tan with black pycnidia. Planting infected seed results in poor stands. All three species of fungi are seedborne and carry over in crop residue. Rainfall and heavy dews are necessary for infection. No infection occurs when the relative humidity is below 80 percent.
Early infection causes complete crop loss due to seedling death.
Late infection results in poor plant growth and reduced seed formation. Tissue decay does not develop above the soil line unless the weather is extremely wet. Infection occurs in both wet and dry soils, but is most destructive in wet soils. The use of high levels of fertilizer will encourage continued root development. Nitrogen acts as a suppressant to fungal growth.