What Are Grub Worms?

As your lawn greens up in spring, keep an eye out for brown patches that never turn green. Those dead patches may be due to grub feeding that occurred the previous fall. Also watch out if your turf becomes spongy. Sometimes you can detect sponginess even before extensive brown patches appear. With well-watered lawns, sponginess may be the first clue that grubs are present.

Lawn Grubs, often called White Grubs, are the immature form of different Scarab Beetles, such as Japanese Beetles, June "bugs" (beetles) or the European Chafers. These white, C-shaped creatures have soft bodies with legs near the head. They feed on grass roots (and organic matter in the soil), causing sections of grass in the lawn to die. To check if grubs are to blame for your dead patches, lift a piece of your turf. If grubs are the culprit, the dead patch will roll up like a carpet, or you'll be able to pull up the grass and see that it has no roots. Irregularly-shaped dead patches appear in your well-irrigated lawn in late summer or early fall. Check your turf using the technique just mentioned.

White grubs eventually turn into adult beetles that emerge from soil to mate and lay eggs. Most Scarab Beetles have a one-year life cycle; June Beetles have a three-year cycle. Timing varies by Beetle species and region, but generally adults emerge from soil, mate, and lay eggs over the course of two to three weeks in early to midsummer. Depending on soil moisture and temperature, eggs hatch about two weeks after being laid, in mid-to late summer. The new generation of root-munching pests begins feasting immediately after hatching. Peak feeding occurs in early fall. Typically, the pests operate a few inches below the soil surface, but burrow deeper (up to 8 inches in northernmost areas) before winter arrives.

Grub damage to lawn is also caused by birds, skunks, armadillos, raccoons or moles are tearing up your lawn —they eat grubs and are trying to uncover them. These animals also dig and eat earthworms, so confirm grubs are present before pursuing any treatment.

• What they look like: Grubs are soft-bodied creatures, creamy in color, with legs near the head. They're usually C-shaped and vary from dime to quarter size. Lawn Grubs are the immature form of Scarab Beetles, such as June Bugs (Beetles), European Chafers and Japanese Beetles.

• Damage: Brown patches appear in a lawn. Grass rolls up like a carpet because roots have been eaten. Turf may feel spongy. Damaged turf can be grasped and lifted up due to root damage.
• Diagnose: Cut a 12x12-inch-square of sod, digging down 2-4 inches. Peel the sod back and look for Grubs. In a healthy lawn, 10 or more Grubs per square foot of lawn will cause damage. Birds, skunks, raccoons and armadillos may dig up lawn to get to Grubs.
• Affected areas: Various species of Scarab Beetle Grubs are serious lawn pests throughout all regions of the country.