Most grubs found in lawns are the larvae of Japanese beetles. Grubs can live in the soil of your lawn, where they eat grass roots, causing the grass to turn brown and die. Serious infestations can also attract wildlife that feed on grubs and cause further damage to your lawn. It is important to find and control grub infestations in your lawn before they spread and become unmanageable. The University of California suggests that nematodes, small unsegmented worms that kill grubs, may be the best way to exterminate grubs in a lawn.
Look for Japanese beetles, the adult form of grubs, to determine where in the soil they might lay eggs.
Inspect the lawn for irregular brown patches that lift and peel away like a rug, which may indicate a grub infestation.
Remove a small patch of grass and count the number of visible grubs. Five or more grubs per 3-inch square indicate an infestation severe enough to require treatment.
Mix the beneficial nematodes with water and spray them evenly on affected areas of the lawn using a lawn sprayer in the late afternoon or early evening, as direct sunlight and intense heat can harm nematodes.
Water the treated areas of the lawn thoroughly after treatment.
Check the lawn for grubs approximately two weeks after the initial application. If necessary, treat the lawn with nematodes again.