Sod Webworm Damage

Sod Webworm

• Sod webworms spend the winter in small web-spun tents a few inches below the soil's surface. In the spring, caterpillars emerge to eat grass blades. Pests also spin webs of silk that weave leaves and soil together inside of the thatch layer. The thatch is the brown organic material between the grass and soil. Gardeners may see buff-colored moths fly over the lawn or resting on grass blades to lay eggs.

Damage

• Sod webworm populations may skyrocket in healthy grass. You may see yellow or brown patches appear within the yard that indicate their presence. Left untreated, these discolored patches grow larger until large areas of the lawn die out. Grass declines in health during droughts or during hot temperatures, because it can not bounce back from the damage. Because sod worms are nocturnal, they are difficult to see during the day. Gardeners may sift through grass blades to look for their silk tunnels, advises the University of Rhode Island.

Cultural Control

• Provide enough water for your grass during periods of drought to help the grass withstand the damage. Irrigate the lawn in the morning. Avoid mowing your grass under 3 inches in height, according to Cornell University. Low grass blades contributes to weak root systems, which can cause grass to die out. Dead areas of grass may be dug out and reseeded. If there is extensive sod webworm damage, use a pesticide to control their numbers.

Chemical Control

• Apply a pesticide chemically formulated to kill sod webworms to your lawn in the late afternoon. The fresher the chemicals, the better success rate you will have killing the pests. Water the pesticide into the thatch. Help prevent sod webworm damage by applying pesticides two or three weeks after you see moths flying over your lawn, suggests the University of Rhode Island. Young caterpillars are vulnerable to pesticides. Wait two days after applying the pesticides to mow.