Corn leaf aphids also suck sap from leaves, but these aphids do not inject a toxin. Therefore, corn leaf aphid feeding does not result in discolored or dying tissue or foliage. Under severe drought stress, heavy infestations may cause some reddish streaking of top leaves and failure of some heads to completely emerge from the boot. This virus can be a problem in fields in which Johnsongrass is abundant because the grass serves as the overwintering perennial host. The virus disease produces distinct mottling of leaf tissues.
Infected leaves are yellow with light green islands.
Red leaf symptoms occur in highly susceptible varieties in cool weather. The symptoms are more easily seen on young leaves than on older ones. When the plants reach the boot stage, symptoms become less apparent in the leaves, but stunting and poor filling of heads can result. Time of infection determines how much yield loss is likely to occur on susceptible hybrids. If plants are infected before reaching 45 days of age, losses are greater than if infection occurs later.