Sod webworms are the larvae of lawn moths, which hide in the day and fly in the evening and at night. When disturbed during daylight hours, the grayish white to tan moths make brief, erratic flight 1 to 2 feet above the ground. They don’t feed on lawns, but their slender, inch-long offspring chew on grass and as the name ”webworm” implies, spin silken tunnels in lawn thatch. Webworms are brown, gray, or green, with dark spots and long, stiff hairs.
Damage: Grass stems are chewed off at the base, leaving brown patches in the lawn. Birds may make pencil-size holes in the turf while digging for the worms.
Life cycle: While in flight, moths drop eggs on the lawn. After hatching, the caterpillars feed by night on grass blades and stems; they can overwinter in the soil. There are usually two or three generations a year, but in the warmest areas, reproduction is continuous.
Notes: For a resistant lawn, plant rye grasses or fescues infected with beneficial endophyte fungi (ask for these types at your nursery). To detect sod webworms, soak a square yard of lawn with a solution of 1 tablespoon household detergent in 1 gallon of water; if 15 or more worms appear, take action.