Sod Webworm / Lawn Moth Facts

Pest Identification: Sod webworms are the larval stage of lawn moths. They appear as pinkish-white to yellowish-brown worms about 3/4 of an inch in length, are covered with fine hairs, and often have a distinctive double row of brown or black spots along their back. These insects feed at night and damage usually appears most heavily during early August and, sometimes, June.

The adult moth is also about 3/4 an inch long. They are whitish or brownis in color, fly close to the grass when disturbed, and, when at rest, fold their wings around their bodies. It should be noted that, while the appearance of adult moths could be an indication of future damage, it does not always prove the case. These moths are known to fly significant distances during the night and, if you see some in your yard, they could simply have come from another infected area.

To check for the presence of the damaging larva, it is easiest to use a soap disclosing drench. To do this, just mix two tablespoons of liquid dishwashing detergent with two gallons of water and sprinkle the mix over a square yard of turf you suspect might be suffering from an infestation. If there are sod webworms in your lawn, within a few minutes you should notice the appearance of larva. If 10-15 are spotted within one square yard of your lawn, then treatment is recommended.

Damage Identification: Initial damage from sod webworms appear as small brown patches roughly the size of a quarter to three inches in diameter. If an area is heavily infested, these relatively small spots may run together, creating larger, irregularly shaped brown patches.

On a closer level, individual grass blades will appear notched on their sides where they have been chewed. It is also common for blades to actually be chewed off close to the soil, leaving areas with brown stubble.

Control/Treatment: Unless the damage is particularly severe, it can usually be handled with simple maintenance techniques, such as watering and fertilizing the affected areas well and reducing thatch build-up.

If your area is experiencing a drought that causes water restrictions to be imposed or when close mowing procedures are being used, your lawn may not be able to simply outgrow the damage, however. In these instances, pesticides, such as Talstar One or Acephate, are recommended. It is best to apply a pesticide in the late afternoon, so that it will be freshly applied when the sod webworms emerge to feed in the evening.

Grass Types Most Susceptible to Infestation: