Armyworms & cutworms

Caterpillars (larvae of night-flying moths) that chew foliage. Fall armyworms have a pale inverted Y on the head and four dark spots arranged in a square on the last segment; cutworms are smooth, gray-to-brown caterpillars that curl into a C when disturbed. Look for larvae in thatch or soil by day and active feeding at dusk; a soap flush brings them to the surface. Birds feeding heavily on the turf can signal an infestation.

Irregular brown, chewed or skeletonized patches that can appear almost overnight as larvae feed; fall armyworm damage often radiates outward from egg-laying sites. Cutworms clip blades near the crown, creating small pockmarks or ball-mark-like depressions on greens. Because feeding is on leaves rather than roots, healthy turf can often recover once larvae are controlled.

Both are moths with complete metamorphosis (egg, larva, pupa, adult). Females lay eggs in masses on grass blades and structures; larvae feed for several weeks through multiple instars, then pupate in the soil. Multiple overlapping generations occur per year, with the most in the warm South; northern populations of fall armyworm are re-established each summer by moths migrating from the South and do not overwinter in cold climates. Development accelerates in warm weather.

Damage is most common from mid-summer into fall, often flaring suddenly when large larval populations move across turf. Fall armyworms can sweep across a stand as a group, leaving a sharp line between eaten and intact turf; cutworm injury is more scattered and is conspicuous on closely mowed golf greens and tees.