Corn Leaf Aphid, Rhopalosiphum maidis
(Hemiptera: Aphididae)

The corn leaf aphid is distributed throughout the United States in areas where corn is grown, but is relatively uncommon on corn in the northwestern states where it prefers to feed on barley. The corn leaf aphid overwinters as adult females and 20 to 40 generations may occur per year. The nymph is pea green with red eyes and eventually becomes darker green with darkly pigmented appendages. The adults are bluish-green to almost black. A fine white powder covers the entire body. Adults may be winged or wingless, and the winged form usually has three black spots on the abdomen.

Host plants include numerous grasses and cereal grains but the only vegetable crop that is affected is corn. Weeds that serve as alternate hosts are barnyardgrass, buffalograss, crabgrass, foxtail, and Johnsongrass. Numerous natural enemies attack corn leaf aphid and help to keep populations under control. The corn leaf aphid causes damage by feeding on the silks, leaves, and tassels of corn plants. Excrement that is produced by the aphids supports the growth of sooty mold that causes an unappealing appearance of the ears. The corn leaf aphid is capable of transmitting numerous plant viruses. Population densities can be estimated using sampling techniques such as infrared sensitive photography, sticky traps, or visual examination. Systemic insecticides can be applied to young plants or to soil, soon after plant emergence from the soil and tend to be relatively effective. In many areas, the corn leaf aphid is not considered to be a serious pest and insecticides are not applied. Cultural control techniques include early planting and host plant resistance.

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Corn leaf aphids, Rhopalosiphum maidis, colony of mixed
ages.
(Photographer: P. Choate, University of Florida)

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Corn leaf aphid, Rhopalosiphum maidis, winged adult.
(Photographer: P. Choate, University of Florida)

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