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. The use of three year rotation, well-drained soil, and the liberal use of fertilizer will help reduce losses from this disease. Control aphids that transmit the virus.