The fall armyworm is a caterpillar about one and a half- inch long, varying in color from green to almost black. Each segment has four black spots on the back, arranged in a square near the end. On older caterpillars, there is a white inverted Y on the forehead.
Fall armyworms feed on a variety of plants, including forage grasses.
It's probably a good idea to keep an eye on hayfields and pastures. The problem starts as a small brown patch in fields. Circular patches can reach 10-20 feet in diameter, according to Flanders. Flanders adds that once the fall armyworms reach about three-fourths inch in length it's not economically feasible to control them. The only thing to do at this stage is salvage the forage by intensive grazing or mowing.