Young plants appear normal, but become stunted as they develop. Severely affected plants turn yellow. The lower foliage wilts and defoliation occurs. Symptoms continue to progress until death occurs. When the stem is cut, there is a dark brown, discolored band around the vascular system.
Infection occurs directly through the root hairs.
The fungus survives for indefinite periods in the soil. Survival is aided by weeds which are susceptible to the fungus. Infection takes place when the temperature ranges from 55 to 86 degrees F. Verticillium is favored in its development if the soil is alkaline. Some development takes place at pH of 5.0 but all growth is stopped at a pH of 4.0. Control involves the use of long rotations.