Sod Webworms

Sod webworm caterpillars feed on grass blades from the top down rather than on the roots, and St. Augustine grass is one of their favorites. In Florida the main species is the tropical sod webworm, and full-grown larvae reach roughly 3/4 inch long.

Identifying Sod Webworms in Florida Lawns

The main species in Florida lawns is the tropical sod webworm. Its caterpillars are greenish to tan with rows of dark spots along the body, and they curl into a C shape when disturbed. The adults are small, dull tan to brown moths. When you walk or mow across an infested lawn, they flutter up in short, zigzag flights and quickly settle back into the grass.

Beyond St. Augustine grass, they also feed on bermudagrass, zoysiagrass, centipedegrass and bahiagrass. Larvae feed at night and rest in the thatch during the day. Young larvae scrape the leaf surface, leaving thin, see-through patches, while older larvae chew notches and can strip blades down to the midrib. Pupae form in the thatch or at the soil surface.

• Fall armyworms are larger caterpillars with a pale, upside-down Y on the head, and they can move across a lawn in groups.
• Grass loopers move with an inchworm-style arch.
• Chinch bugs are tiny black-and-white insects, not caterpillars, and cause yellowing rather than chewed blades.

Damage is usually heaviest from late summer into fall and is often first noticed in sunny areas. In South Florida, larvae can be active year-round. Birds probing heavily in one part of the lawn can be a hint that webworms or other caterpillars are present. To confirm and manage them, see how to get rid of sod webworms.