How to Identify Worms That Are Damaging Your Lawn. Got brown patches on your lawn during the summer months? They might not be the result of the sun-it's possible that you have a sod webworm problem. Here's how to identify worms that are damaging your lawn.
Look for brown patches on your lawn.
Head out to your lawn at night with a flashlight and see if you can catch a worm in the act of eating your lawn. Sod webworms hatch from eggs and feed on blades of grass at night. By day they burrow just below the surface of the soil.
Identify the worm if you see one. Fully grown sod webworms are about 3/4-inch long, with dark shiny-brown heads. Their color can be greenish, beige, brown or gray, depending on the species. Their abdomens sport four parallel rows of dark spots, with a long, stiff hair growing out of each spot.
Try flooding the area where you suspect that you have sod webworms with water, if you couldn't find any by flashlight or if you want to see how bad the infestation has become.
Count the sod webworms that are displaced to the surface by the water. If you see more than 15 sod webworms per 1 square yard, you'll need to treat your lawn to get rid of them.