2000 Damage from armyworms in turf in northwestern and southwestern Illinois has been reported. Although common in turf, armyworms rarely become numerous enough to be much of a problem. However, when they are numerous, they can eat off every blade of grass in several thousand square feet of turf per night. In the evening you have nice, green turf, and in the morning all you have are crowns and thatch. Mature larvae are brown to black with five orange stripes, one down the back and two on each side.
Small caterpillars are dark in color with less noticeable stripes.
Caterpillars hide in the thatch during the day and come out to feed at night. Armyworms spend the winter in the southern United States, and the moths fly north in the spring. Armyworm moths are about 1 inch long with tan to grayish-brown wings. Each front wing has a single white dot near the center. The female moth lays her white eggs in rows or groups on grass blades and rolls the grass blade around them.