Sod webworms increase in importance when many new lawns are being established and when old lawns are receiving extra care. Sod webworms are active during the night hours feeding on grass blades. They drag the blades into silken tunnels that they construct on the soil surface.
Damage first appears as brown trails or small irregular brown spots in the lawns.
As the larvae grow the trails expand, becoming large brown areas of injured grass. Sod webworms overwinter in the silken tunnels. They become active in the spring and appear as lawn moths in late June and July. The moths have a wingspan of less than 1 inch and are a light brown in color. They hide in the grass or in shrubbery around the lawn during daylight hours.