Corn Leaf Aphid

Rhopalosiphum maidis

Heavy infestation of corn leaf aphids
Heavy infestation of corn leaf aphids. Photo courtesy of Frank Peairs. Licensed under CC BY 3.0.
The corn leaf aphid is a relatively minor pest of corn, sorghum, and small grains. It has a very wide distribution range.
Corn leaf aphids are blue-grey in color. They are extremely small (1/25"). Adults have transparent wings, while nymphs are smaller and wingless. Corn leaf aphids are typically found on or near the tassel or whorl.
Adult and nymph corn leaf aphids
Adult and nynph corn leaf aphids. Photo courtesy of Merle Shepard, Gerald R.Carner, and P.A.C Ooi. Licensed under CC BY 3.0.
Aphids pierce the plant and suck out the juices. This can result in the death of upper leaves in the case of severe infestation, but normally does not have a significant impact on yield. Aphids can also be a vector for diseases, particularly Barley Yellow Dwarf Virus.
Insecticides are available for controlling corn leaf aphids. However, these tiny insects are usually naturally controlled by enviornmental factors and predatory insects. Significant infestations in seed corn fields may justify treatment. Always read and follow all label instructions.