Sod Webworm: How to Control Them Naturally

Sod Webworm

Crambinae (several species)

Spotted caterpillars that chew grass blades at night from silk-lined tunnels in the thatch, leaving small brown patches that grow.

How to control sod webworm

Use: Ecomask Spray (also works: Scanmask Spray, Heteromask Spray, Scanmask Topdressing, Ecomask Topdressing)
When: Anytime the larvae are active.
Where: The thatch in and around damaged patches, especially their edges, where the larvae gather. Apply in the evening.

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What it looks like

Sod webworms are the caterpillars of small, buff-colored moths that fly over lawns at dusk in a zigzag pattern. The caterpillars are grayish tan with rows of dark spots.

The caterpillars live in silk-lined tunnels in the thatch and feed at night. There are one or two generations a year.

Damage

Sod webworms chew the grass blades off near the ground, leaving small brown patches that grow larger. Look closely and you'll see chewed or notched leaves and small green pellets of droppings in the thatch. Damage is worse in hot, dry weather and is most obvious in July and August.

How nematodes help

The beneficial nematodes in Ecomask wait in the thatch and attack the caterpillars as they move through it. The University of California calls them "a valuable control measure" for sod webworms. They work best on young, small caterpillars.