Arkansas is home to two kinds of armyworms – true armyworms and fall armyworms. During their last two stages of growth, they eat tremendous amounts of grass so scouting pastures for armyworms is essential, says Dr. David Fernandez, Cooperative Extension Program livestock specialist at the University of Arkansas at Pine Bluff.
True armyworms are usually a springtime pest, especially in northern Arkansas on cool season grasses. But they can also be a problem in southern Arkansas. Fall armyworms are more common in southern Arkansas, and they appear in midsummer especially in bermudagrass pastures, he says.
Armyworms easily avoid detection by the casual observer which is one reason damage seems to appear overnight. True armyworms eat at night so their damage is especially noticeable in the morning. Armyworm damage looks like brown drought damage because of dehydration from the leaves of the damaged grass. You will also find frass, which are small, dark seed-like caterpillar droppings.
“The best time to check for true armyworms is at night and for fall armyworms early in the morning or in the late afternoon when they feed,” says Dr. Fernandez. Otherwise, you’ll have to get on your hands and knees and look under the thatch to find them where they rest during the day.