Sod webworm (Several species)

What do they look like?

Sod webworms are small caterpillars living in silk-lined tunnels threaded through the thatch and soil. The adults become light-colored moths, which will hover around the lawn at nightfall. Maybe their rooting for the caterpillars do more damage. There are more than 20 different species, with 2-3 species in each geographic region.

How do we know we've got them?

The best way to know if you have sod webworm is to get on your hands and knees and look for those silk-lined tunnels. You might even see the larvae themselves. Another obvious sign is heavy moth activity at night. Their damage is most evident in over-dry lawns and south-facing slopes. You can distinguish damage from the webworms because turf will not roll up like it would with grub damage, and there will be burrows and chewed grass, which aren't seen in other diseases or caused by dog urine.

How do they damage our lawns?

The larvae chew on leaves and stems, exposing the crowns. The more stressed the plant prior to attack, the greater the potential for damage.

How do we get rid of them?

The best way to control this insect is with a healthy lawn. Even if they are present, the natural predators in a healthy lawn will keep them under wraps. You only have to think about taking action against sod webworm if you find, after sampling, that there are 10-15 larvae for every square yard of lawn. Even then, attack the larvae, not the moth. Take note when the moths fly, then treat for larvae 10-14 days after this date. Biorational controls such as the nematode Steinernema carpocapsae have proven effective.