How to Identify and Repair Sod Webworm Lawn Damage
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Lawn moths are the flying adults of the sod webworm. If you've got a beautiful, thick lawn, you may get singled out to host a population of these lawn killers. The adults can (and do) fly to the lawns of their choice. They actually pick the better lawns in which to lay their eggs.
Sod webworms attack many varieties of grass, but are especially deadly on bluegrass lawns. The early warning of a possible sod webworm problem comes when you see small, brownish-gray moths flying in a jerky, zigzag pattern over the lawn in the early evening. These adults don't damage the lawn, but during these evening flights the moths are laying the eggs that soon hatch into the larvae (or worms) that actually feed on the turf. Damage almost never appears in heavily shaded areas. On the other hand, hot and dry areas are favored by webworms.
Tip #1: Identify that it's webworm damage your lawn is suffering from.
Damage first appears as dead patches scattered through the healthy grass. By the middle of the season, large parts of the lawn may be dead. Sod webworm scattered through the healthy grass are often confused with drought stress by the casual observer.
Sod webworms chew the grass blades off very near the thatch layer and drag them into tunnels they build in or above the thatch. The result is patches that look like they've been scalped.
Most severe damage shows up in July and August during hot weather.
Tip #2: Make sure you know what you're dealing with before you begin sod webworm treatments.
Winter is spent as partially grown larvae several inches deep in the soil. After the first generation of adult moths have laid their eggs, the resulting worms feed for several weeks before going into the resting, or pupil stage, prior to emerging as new adult moths. There can be two, and as many as three, generations of sod webworms per season.
Tip #3: Locate where the webworms are in your lawn.
The surest way to identify sod webworm damage is to locate the tiny green pellets they leave as excrement. On hands and knees, spread the grass between areas of healthy and dead grass (the insects work outward into the healthy grass) to find evidence. If pellets are located, the larvae are nearby. The worms themselves are 1/4'' to 3/4'' long and have a segmented body like a caterpillar that is brownish or dusty green. The segments of the body each have several dark spots with two or three stiff, spiny hairs protruding from each of the spots.
Things to remember when repairing sod webworm damage:
Sod webworm adults are lawn moths that do no damage to the lawn, but lay eggs in the early evening.
The worms (or larvae) do their damage by chewing the grass blades off at the thatch line.