Sod webworm damage

Sod webworms are the larvae of small moths that fly in a distinctive zigzag pattern close to the lawn surface at dusk. Adults do not damage grass -- they are simply the indicator that larvae are present or will soon be. The caterpillars that hatch from their eggs feed on grass blades at the soil.

Sod webworms are the larvae of small moths that fly in a distinctive zigzag pattern close to the lawn surface at dusk. Adults do not damage grass — they are simply the indicator that larvae are present or will soon be. The caterpillars that hatch from their eggs feed on grass blades at the soil surface, creating ragged, irregular patches that progress from small to large over 3—4 weeks.

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Species overview

Per Cornell Cooperative Extension, numerous sod webworm species affect lawns in the United States. The most common include:

• Larger sod webworm (Pediasia trisecta) — widespread in the Midwest
• Bluegrass webworm (Parapediasia teterrella) — northeast and north-central states
• Tropical sod webworm (Herpetogramma phaeopteralis) — Florida and Gulf Coast, on warm-season grasses

Per UF IFAS Extension, the tropical sod webworm is a significant pest of St. Augustine grass, bermuda grass, and zoysia in Florida and the Gulf South — distinct from the temperate species affecting cool-season northern lawns.