Corn Leaf Aphid
Rhopalosiphum maidis (Fitch)
Identification / Life Cycle
The oval-shaped, wingless adult is approximately 2/25 of an inch (2 mm) long. It is pale bluish-green in color with black antennae, legs, and cornicles (Figure 7.9). The head is marked with two longitudinal dark bands and the abdomen with a row of black spots on each side. The body often seems to have a powdery coating.
The first spring adults are winged females which fly in search of suitable host plants, and shortly thereafter give birth to live nymphs which usually develop into wingless females. Under favorable conditions, more winged females develop and migrate. Males are rarely found, and females continue to reproduce without mating (no eggstage is known for corn leaf aphid). Reproduction slows in winter and summer and is most rapid during cool weather. Therefore, corn leaf aphid tends to be a problem on winter grains in the spring.
Establishing level of risk
The corn leaf aphid shows a preference for barley, sorghum, and corn. It also infests many other wild and cultivated grasses. An occasional pest of winter wheat, the corn leaf aphid sometimes occurs on seedling wheat in the fall. It is a vector of barley yellow dwarf virus.
Similar to other small grain aphids, corn leaf aphid can be attacked by various predators and parasitoids that are common in wheat fields.