How to Identify a Lawn Infested With Grubs

Several species of beetles have larvae that feed on the roots of lawn grasses. These grubs can invade a lawn and destroy the root system, leaving brown spots or even an entirely dead lawn. Damage from grubs is most obvious in the summer, but can be mistaken for damage from under-watering or a lawn disease. Learn the signs of a grub infestation and a way to examine the soil to ensure the damage is from grubs specifically.

Sharp shovel

Monitor your lawn for splotchy, irregularly shaped brown patches, especially in the summer when grub activity is at its peak. If your lawn has a grub infestation, the damage will occur in sunny spots. Shady lawns do not typically experience grub infestation.

Keep an eye out for raccoons or skunks in your yard, especially at night. These animals will come into a yard infested with grubs and dig up the grass to get at the larvae. Look for signs of an animal digging in spots of grass that were already browning.

Grasp a handful of turf grass and gently pull upward. Grubs feed on the roots of the grass, so an infested lawn will have grass that tears up easily. If the grass comes away from the soil with minimal effort on your part, there is root damage that may be from grubs.

Use a sharp spade to cut up a 6-by-6 square of grass to expose the topsoil underneath. If the spot has more than two or three grubs in the top 3 inches of soil, the lawn probably has an infestation.

Repeat the lifting of turf in 6-by-6 squares in at least 12 random spots throughout the yard. If your lawn has browning, dig up the samples in the browned areas. Grubs will sometimes only infest parts of the lawn, so you will not need to treat the entire lawn with insecticide if you do not find infestation throughout.

Replace the turf samples. Tap them down with your foot and water them.