Appearance: Caterpillars approximately 3/4 to an inch long. Beige, green, brown or gray, with four rows of distinct brown spots along the abdomen.
Type of Damage: Browns out the lawn causing it to pull up like a rug.
Active Damage Season: Late June – September
Treatment: Insecticide

How do I know if I have Sod Webworm?

In the caterpillar stages, Sod Webworm is usually ranges between 3/4 to an inch long. While their heads are a dark brown, their bodies will either be a beige, green, brown or gray, depending on the species. Four rows of distinct brown spots line the abdomen from which stiff hairs protrude. It is in these caterpillar stages that the damage is done to your lawn.

The adults are a buff or brown moth with up to a one inch wingspan. You will see them flying above the lawn in jerky zig-zag patterns in the early morning or late evening, or if you mow or disturb the lawn. At night, they are attracted to lights. The adults do no damage to the lawn.

The damage caused by the caterpillars causes the lawn to brown out in spots and spread rapidly. Pull on these areas with your whole hand. If Sod Webworm is at fault, it will pull up like rug and you will see the larvae on the soil.

When is Sod Webworm most common?

After the dormant caterpillar transforms and emerges as a moth, the first generation begin to lay the years first generation of eggs late in June. During their 35 days as a Caterpillar, a Sod Webworm can eat up to four square feet of grass. This life cycle continues until the weather starts to cool in late fall and the larvae curl up for the winter in the soil.

How do I get rid of Sod Webworm?

To control the problem, apply insecticide directly to the affected areas and check back weekly for improvement. Repeat until the spreading stops (should be within a couple of weeks). The lawn will then naturally heal itself as it continues to grow and spread back into the affected area(s).

For more information on sod webworm click here: http://extension.usu.edu/files/publications/factsheet/sod-webworm07.pdf