Problem: Armyworms (Lawns)
Armyworms (Pseudaletia unipuncta) and fall armyworms (Spodoptera frugiperda) are the larvae of tan to gray moths with a 11/2-inch wingspan. The closely related caterpillars both winter in the South, with fall armyworms going farther south than armyworms. In spring they migrate as far as the northern tier of states and are active throughout the growing season. Adults lay eggs in dry grass and thatch. Eggs hatch into light green larvae that feed on grass blades. Armyworms eat any grass, including grain crops, grassy weeds, and lawns. Some species also eat other plants and are serious vegetable-garden pests. Larvae grow to 11/2 inches long, becoming darker as they mature. Several generations may be produced in a year. They are called armyworms because they migrate in large numbers to new food sources. Migrating during the day and feeding at night, they may appear suddenly and do a great deal of damage in a brief time.
To make lawns less attractive to armyworms, reduce thatch and eliminate soggy areas. Very large armyworms (1 1/2 inches) dig into the soil to pupate, and control may be difficult.