Pest profile

Tropical Sod Webworm

Herpetogramma phaeopteralis · Lepidoptera: Crambidae[2]

Tropical sod webworm caterpillars feed at night on warm-season grasses and can strip lawn patches by fall.[1]

Tropical sod webworm moth, a dingy brown triangular moth, resting on a surface
Tropical sod webworm moth, a dingy brown triangular moth, resting on a surface. (c) Alexis Smith, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Moths are dingy brown with about a 3/4 inch wingspan, holding wings in a triangle at rest.[1]
  • Young larvae window-feed on the upper blade surface; older ones chew whole sections off blades.[1]

Look-alikes

Look-alikeHow to tell them apart
Other sod webwormsA tropical species of warm-season turf.[1]

Where it lives

In North America it has been recorded from Florida, Georgia, Louisiana, Texas and Hawaii.[1]

US map: public records from 20 states since 1990 (GBIF).

Biology and life cycle

In south Florida adults are present year round, peaking September through November.[1]

Larvae feed at night and hide in thatch by day.[1]

Damage and signs

  • Damage starts ragged and grows into bare areas; caterpillars prefer hot, dry turf.[1]

Health risk

It feeds on grass; UF/IFAS mentions no risk to people.[1]

Control

Pesticides

Several insecticides can control it, with attention to timing, resistance and effects on other organisms.[1]

Common questions

What's chewing my St. Augustine or zoysia lawn in fall?
Tropical sod webworms are a common cause in warm-season lawns.[1]
When do they feed?
At night; they hide in thatch during the day.[1]

Sources

  1. University of Florida IFAS Extension (Featured Creatures), “Tropical Sod Webworm, Herpetogramma phaeopteralis (EENY-541).” edis.ifas.ufl.edu/publication/IN968 (accessed 2026-10-06)
  2. iNaturalist, “Herpetogramma phaeopteralis taxon page (order and family).” www.inaturalist.org/taxa/330489 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.