University of Illinois

Yellowstriped Armyworms, Anyone?

August 14, 1998
With so much late-planted corn in the state this year, none of us was surprised when fall armyworms reared their ugly heads, especially in southern Illinois. Well, a "cousin" of the fall armyworm, the more attractive yellow-striped armyworm, has also appeared this year. John Shaw observed that one of his sweet corn trials in Champaign County is heavily infested. Therefore, we assume that this infrequent pest also may be present elsewhere.

Like the fall armyworm, the yellow-striped armyworm is a tropical and subtropical species that migrates northward as weather conditions permit. When they arrive, the females deposit eggs, which are covered with the female's body scales, in irregular masses on plant foliage. As soon as the eggs hatch, young larvae begin feeding on the leaves. The mature yellowstriped armyworm larva is 1 to 1-2/5 inches long and glossy black to gray, with dark triangular spots along the midline of the back. A yellowstripe is evident along each side of the triangular spots, and there is a black spot above the hind legs. The head is brown, with a netlike pattern. Among caterpillars that feed on corn, yellow-striped armyworms are one of the prettiest. (Maybe you have to be an entomologist to appreciate this.)

Yellowstriped armyworms are occasional pests of corn, usually feeding on the leaves of young corn plants or in the whorl. Moderate infestations are not harmful, as long as the growing point of the plant is not injured. Control with insecticides is not economical unless feeding would cause heavy damage.

Author: Kevin Steffey