Armyworm damage on lawns

Armyworms are the lawn insect that most dramatically demonstrates the difference between "treat quickly" and "treat later." These caterpillars feed above ground -- unlike grubs and billbugs -- which means they are both faster-acting and faster to treat. A lawn that shows early armyworm feeding in.

Armyworms are the lawn insect that most dramatically demonstrates the difference between "treat quickly" and "treat later." These caterpillars feed above ground — unlike grubs and billbugs — which means they are both faster-acting and faster to treat. A lawn that shows early armyworm feeding in the morning can have larvae dead within 24 hours with a correctly timed insecticide application. A lawn noticed three days later may have lost significant turf.

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Species in the United States

Per NC State TurfFiles and UF IFAS Extension, two primary armyworm species damage lawns:

Fall armyworm (Spodoptera frugiperda)

• Primary pest of warm-season lawns in the South and transitional areas
• Damages bermuda grass, St. Augustine, zoysia, centipede grass, and tall fescue
• Most active late summer through fall (August—October in the South)
• Can overwinter in south Florida; migrates north each season on wind currents
• Mature larvae: 1.5 inches, gray-brown with yellow and dark stripes, distinctive inverted Y mark on head capsule

True armyworm (Mythimna unipuncta)

• More common on cool-season grasses in the Northeast and Midwest
• Damages Kentucky bluegrass, perennial ryegrass, and other cool-season grasses
• Feeding primarily in spring (April—June) and fall
• Mature larvae: 1.5 inches, brown with green and yellow stripes