Lawn moths are small pale coloured moths that fly up from grass when disturbed. They will land very quickly, fold up their wings and crawl into the grass.
Lawn Moth (left)-Drgreen.com, Size of lawn moth (right)-Utah State University
They have a long snout and a powdery substance on their wings. The worms of these guys hide in silky white tubes (resembling a long cocoon) near the roots of grass. they are white and active mostly at night. These guys are also called Sod Webworms. They occur in all of the US and most parts of Canada.
Lawn Moth Caterpillar (left)-Laters, Lifecycle-OSU extension Entomology
Eggs are laid in the grass or wherever they happen to fall. Worms hatch and become active in the early spring. There are at least 2 generations a year
Caterpillar damage on lawn
Diet and Damage
They eat grass, roots, corn and many clovers. If you see a large brown patch on your lawn, it is probably caused by these guys. They chew grass down to the roots. Brown patches occur in hot dry spots on your lawn. If you have a nicer lawn then your neighbour then they will pick yours! They are quite fussy. They also eat corn, can skeletonize leaves, notch and chew holes.
Encourage birds in the area where there are webwoms. Put out bird baths right in the areas where they are present as they will eat the worms.
2) Hand Pick
On your hands and knees spread the grass and look for tiny green droppings. The worms are certain to be near. This is a toughie as they are very hard to find but a fine rake to the areas where you know they are present will dislodge them. Drop them in soapy water, or crush them.
3) Predatory Insects
Tachnid flies, ants, braconid wasps, paper wasps, predatory mites and robber flies to name a few. There are some types of beetles as well that eat these guys.
Use a spray of Bt on the brown patches. It is not that effective because it only lasts a few days, breaks down quickly in the sun and can wash off when you water your lawn or rains.
5) Control Clover on Lawns and Irrigate
Webworms love clover so weeding out the clover should help reduce infestation. Making sure that your lawn has enough nitrogen will keep the clover away as well. Usually clover is a sign of nitrogen deficiency. Good irrigation is a must as the worms do not like moist conditions.