Sod webworms live in tunnels constructed in turf thatch or extending to the soil under the turf. These tunnels are lined with silk, soil particles and bits of leaves. They emerge from these burrows to chew grass blades off just above the thatch line, usually at night. The most severe damage usually appears in July and August when it is hot and grass is not growing vigorously. Sod webworm damage is often mistaken for heat and drought stress.

Habitat:
Adult sod webworms rest in the turf grass in lawns, parks, cemeteries and golf courses. They also cause damage to small grain crops and shrubbery. An early sign of potential infestation is female sod webworm moths zig-zagging over turf at dusk, scattering eggs over lawns as they fly. They can lay up to 60 eggs per evening.

If infestation is present, small patches of grass will be chewed off at ground level. Fresh clippings and green fecal pellets, called frass, are also usually present. Larvae, silken tubes and webbing can also be present in the thatch layer and the top inch of soil. In Florida, tropical sod webworms may produce new generations very quickly.

Interesting Fact:
During the short time the sod webworm is in the larval stage, it can eat around four square feet of grass.

Control:
The surest way to tell if you have sod webworms is to find a suspected area of infestation, such as brown patches. Get down on your hands and knees, take your two index fingers and part the grass blades in the area between dead and live grass and look for an area with frass present. This indicates that larvae are close by. The adult moths can fly considerable distances and may be coming from other infested areas.

If you still suspect sod webworm activity but are unable to find the larvae or their frass, use a soap disclosing drench. Simply mix up two gallons of tap water with two tablespoons of liquid dishwashing detergent. Sprinkle this mix over a one square yard of the affected turf. Within a couple of minutes, the flesh-colored, spotted larvae will wriggle to the surface. If you get 10 to 15 larvae in a one square yard of turf, treatment with insecticide is warranted.

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