If you maintain a lawn that happens to benefit from full sun exposure (not shaded) and has become weakened from heat and drought stress you need to be aware of sod webworm and the damage it can cause. This small sod webworm caterpillar (5/8″-1″ in length) can chew off leaves and stems of your cool-season grasses including Kentucky bluegrass, most fescues, perennial ryegrass and bentgrass. It will cause general lawn thinning, followed by small patches of brown and finally leaving behind closely cut/cropped areas. A lawn that is healthy and well irrigated will often tolerate and recover from sod webworm scalping. Weak or drought stressed lawns that have been clipped short by sod webworm may be killed via sun exposure to the crowns of the plant. Adult sod webworm moths (lawn moths) are small whitish, dull gray or tan colored moths that hover over turfgrass at dusk. As these small sod webworm moths flutter across the lawn females drop eggs during flight that settle in the upper thatch layer of your lawn. As many as 500 eggs are laid during a life span of usually less than 14 days. Depending on temperatures, eggs hatch in 4 to 20 days and the larvae develop through usually 6 to 8 larval stages in 4 to 7 weeks. The larvae are beige, gray, brown or a greenish color (depending upon species) with a brownish head. The older larvae chew down foliage around their burrows mainly at night. Most sod webworm have two generations per year. Sod webworm are fairly easy to control on a curative, as-needed basis. Insecticide controls are directed against the feeding larvae, not the moths. A healthy, vigorous turf, balanced fertility and adequate irrigation during dry periods will enhance your lawn’s tolerance to sod webworm feeding. As always, be sure to contact a local lawn professional to help identify sod webworm, evaluate treatment options and analyze if lawn repairs will be needed.
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