How to Treat Webworm Infestation

Bluegrass sod webworm (Parapediasia teterella) can harm crops such as alfalfa as well as to lawns and golf courses. The worm does not kill the grass, but it clips the grass close to its crown. The exposed crown then becomes susceptible to the elements.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• 1 qt. water
• 1 tbsp. laundry detergent
• Insecticide for webworm

1. Identify the worm properly. The worms are the larvae of lawn moths. These caterpillars usually grow to about ¾ inch in length. They have brown spots arranged in rings around their greenish gray bodies. The adult moth is small and whitish gray. Both feed close to the ground. The larvae cause the most problems.

2. Monitor plants for rate of infestation. Force the larvae to the surface. Combine the water with the laundry detergent, and spray this mixture over various 4-square-foot sections of your grass. The soapy mixture irritates the worms, and they come to the surface to escape it. If you have more than two to four webworms per square foot, you must treat your lawn.

3. Mow your lawn in preparation for treatment. It will provide a better base for an insecticide spray. If you have a grass catcher, use it to remove the clippings.

4. Spray your lawn with a chemical insecticide specific to webworm. There are also bacterial insecticides available that kill only webworm.

Tips & Warnings

• Webworms typically have two hatches each year. Normally, if you spray for the first hatch in late June, they will disappear. However, you may need to repeat the process later in the summer.
• It's best to apply the insecticide when no rain is forecast. If the grass is dry and needs watering, only water enough to settle the insecticide around the base of the crown of the grass. Allow the insecticide at least 48 hours to work.
• Remove children and pets from areas sprayed with insecticide. Read and follow insecticide directions carefully.