Outbreaks of maize chlorotic dwarf typically are limited to areas of the field with infestations of rhizome johnsongrass. MCDV is not known to be seedborne. Factors Affecting Disease Development Outbreaks of the corn virus complex are not always predictable and will occur only if the crop is susceptible to infection, the viruses and insect vectors are present, and environmental conditions favor virus spread and symptom development. If one of these factors is missing, then little or no disease will develop. However, when these factors come together, unexpected outbreaks of virus diseases can occur.
Several factors can influence development of virus diseases.
Corn hybrids differ greatly in their susceptibility or tolerance to the virus complex, so hybrid selection can influence disease development. Weather and other factors that affect the number and activity of insect vectors can also have an impact on the virus complex. Late-planted corn is more susceptible to the virus complex. Compared to corn planted on time, late-planted corn is at an earlier stage of crop development during periods of peak activity of insect vectors. Earlier infection of corn usually results in more severe symptoms of the virus complex and greater yield loss.