Sod Worms in California

Identification

• Although referred to as sod worms, these insects are not really worms but the larvae of moths. The larvae of all three species look similar with a light brown or light brown-yellow body and two rows of dark spots along their dorsal side. They come out to feed at eat at night and hide in burrows during the day.

Damage to the Grass

• Because the larvae feed at night, you may not see the infestation. Instead, you will most likely first notice the damage to your lawn. Sod worms eat parts of the leaf or pull off parts of the grass blades and take them into their burrow to eat. Lawns with sod worm damage will have grass that looks chopped and eaten. The grass may also be brown or develop bare patches. If there are few sod worms, then the damage will be minor and often unnoticeable. However, when an infestation becomes severe, the damage will become obvious.

Finding an Infestation

• If you suspect an infestation of sod worms, you need to confirm it to treat it properly. You can look for the tunnels made by the larvae. The tunnels will have a silk lining. You may also see tiny green fecal pellets in the dead grass patches. Applying a soapy water solution consisting of 2 gallons of water mixed with 2 tablespoons of dishwashing soap to the area will make the larvae come to the surface so you can see and identify them.

Treatment

• Predators of sod worms include the earwig, ants, and paper wasps, so avoiding the use of chemical controls will help retain these beneficial insects. The University of California Statewide Integrated Pest Management Program says damage is not usually noticeable in lawns mowed at a height above 2 1/2 inches, adding that thatch removal can also aid in reducing infestations. Applying the bacterial insecticide Bacillus thruingiensis (Bt) to the lawn can help, though UC IPM notes that it breaks down quickly in sunlight and washes off leaves easily. Steinernema carpocapsae nematodes are another control measure, according to UC IPM.