The full-grown 1-1/2 inch armyworm has a greenish brown body with a thin stripe down the center and two orange stripes along each side. The head is brown with dark honeycombed markings. Eggs are small, greenish-white, globular, and laid in clusters of 25 or more on the leaves of grasses. The adult moth is tan with a tiny white spot in the center of the forewings. The moth has a wingspan of about 1-3/4 inches. Armyworms overwinter as partially grown larvae in grasses or small grain fields. When warm spring temperatures return, armyworm feeding resumes. Armyworms may move onto corn during this period. When feeding is completed, Larvae pupate just below the surface of the soil. Adults of the first generation emerge in May and June and feed on nectar for 7 to 10 days before beginning to lay eggs. There are three to four generations per year in Kentucky.

Damage

    Armyworm damage may occur in corn shortly after planting into killed sod or small grains. Usually, these insects are present at planting and move to small corn as the cover crop dies. Infestations may be spotty and intense. Ragged leaf feeding in the spring and early summer is evidence of armyworm feeding. Armyworms usually feed at night and damage corn by chewing leaves. They prefer to feed on the succulent leaves in the whorl first. Feeding begins at the leaf margins, and they may strip the entire plant leaving only the midrib of the leaves. During the day, armyworms hide in the soil or underneath ground cover. Corn can usually recover from light to moderate feeding by armyworms without significant yield loss. However, severe damage, particularly if the growing bud is injured, can cause significant loss in yield.

Recommendations

    Control is justified if an average of 2 or more larvae are found on 25 - 30 %of the plants or 1 larvae found per plant on 75 % of the stand.

For more information, see Entfact 109