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How to Kill Sod Webworms

Sod webworms are the larvae of lawn moths. These pests eat grass and dig tunnels in the soil. Their tunnels are lined with silk similar to a spider's web, which gives the larvae their name. The grass above their tunnels browns and dies when the webworms come out of the tunnels to eat the grass. Significant infestations of sod webworms can kill large patches of your lawn; killing the webworms will help to save your lawn.

Water the affected area to a depth of 1/2 inch two days before applying chemical agents.

Follow the label instructions on your pest control product, and apply it only to the areas of damaged lawn.

Water the pesticide into your lawn with 1/2 inch of water.

Mow the lawn to 1 1/2 inches high.

Keep your lawn watered to a depth of 1/2 inch for one week to improve the penetration of the pesticide.

Chemicals For Sod Webworms

Horticulturalists at University of California-Davis (UC-Davis) recommend insecticides containing the active ingredient spinosad as the most useful control of sod webworms, taking into account efficiency, impact on the environment and natural enemies. kurstaki nematode), a bacteria, rank second and third on the UC-Davis list of effective controls of sod webworms. A single-celled microorganism, BT lives in soil and kills many species of moths. Look for brownish or whitish moths up to 3/4 inch long or slender, grayish larvae up to 3/4 inch long. Damage caused by feeding webworm larvae may not be noticeable in grass mowed above 2 1/2 inches high.


Verify that you have sod webworms before starting treatment. Combine 2 tbsp. liquid dish soap with 2 gallons of water. Evenly pour the soapy water over a 1-square-yard area of your lawn where you notice 1/4- to 3-inch areas of brown in the lawn. Wait two to three minutes for the webworms to come to the surface. Count them and consider treating your lawn if you see 10 or more larvae.

Look for any of the follow in your pesticide as the active ingredient for effective treatment of sod webworms: acephate, beta-cyfluthrin, trichlorfon, carbaryl, deltamethrin, chlorpyrifos, lambda-cyhalothrin or bifenthrin.

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