Cranberry Girdler: The Gray Lawn-eating Webworm

Is your lawn brown despite water from rain and sprinklers? Cranberry girdler, also called subterranean webworm, may be eating the roots of your lawn.

Life Cycle

Adult cranberry girdlers emerge mid-June as moths. After mating, females drop hundreds of eggs per week. The eggs hatch in nine to 11 days. Larvae bury themselves in the soil and start munching on the roots and crowns of the lawn. When the colder months come, the larvae spin a silk tunnel and overwinter. In the spring they turn into pupae in preparation to become adult webworms. The life cycle starts over again when the webworms emerge as moths in June.


Cranberry girdlers look a little different than other webworms. The larvae have orangish, brown heads and are dirty-white or gray colors. Adult moths have protruding “snouts” and tube-like wings when resting against their bodies. Their wings have brown and cream stripes, and their front wings are a light sandy color.

Lawn Damage

Larvae actively eat grass crowns from late summer into fall killing the lawn. On the other hand, lawns that turn brown during the hot mid-summer months often wither from drought stress and need more water.

To test for cranberry girdler firmly pull on the grass. If your lawn is infested with the insect, the grass will come up easily, and the roots will remain in the ground. After the lawn is pulled up, you will see the bug. In drastic cases, the lawn will roll up like a rug.

To avoid cranberry girdler damage, make sure your yard is properly irrigated and fertilized according to the season and mowed high in the summer. These insects like to eat overwatered cool season grasses, such as Kentucky bluegrass, bent grass, and fine leaf fescues.


After the bug has been eating at the lawn, insecticide will get rid of the webworm once the webworm touches the chemical. If the lawn goes through the fall and winter untreated the grass will be dead in the winter and unable to grow back in the spring.

Stewarts uses a granular chemical to treat for insects that eat grass. Call 801-226-2261 if you think your lawn has cranberry girdler.