They come from several species but have similar habits. Moths are gray or white and fly in zig zag patterns in late evening hours. When they land, they keep their wings closed rather than spreading them like other moths. Damaged grass discolors to a brown in saucer sized patches in the hottest driest areas. At the soil level, the grass blades in damaged lawns are chewed and there will be white silky tubes containing worms at the bases.
Female moths drop eggs as they fly in their zig zag pattern.
The eggs then hatch into worms, which feed on rainy, cloudy days and at night on the grass blades. The white silky tubes hide these worms during the day and in just a matter of a few days an infestation of sod webworms can kill off an entire lawn. Apply an insecticide containing diazinon, chlorpyrifos or isofenophos when you first notice the damage in your lawn, after carefully raking out all dead grass and mowing the area thoroughly. Applying insecticide in the evening hours is most effective as that is when the worms and moths are most active. After treatment avoid cutting or mowing the lawn for 3 to 5 days.