Damaged, discolored grass? Could be sod webworms. Find out what they are and what to do.
What is it?
Sod webworms are also known as night-flying lawn moths. They come from several species but have similar habits.
What does it look like?
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. Their worms are 1/4 to 3/4 inch long, and are light brown or gray with black spots. Damaged grass discolors to a brown in saucer sized patches in the hottest driest areas. Areas may expand to form larger irregular patches from mid-May to mid-October. At the soil level, the grass blades in damaged lawns are chewed and there will be white silky tubes containing worms at the bases.
How does it manifest?
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.
What can you do about it?
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. Treat the lawn regularly every 2 months until early summer to kill off all eggs and emerging worms. Treated lawns recover rapidly.