Grubworms or White Grubs—By Either Name,
They're a Pest

White grubs, also called grubworms, are the C-shaped larvae of a large group of beetles called scarabs. The larvae of many species attack turf grasses.

Stages

Scarabs go through the regular insect life cycle, from eggs to larvae to pupae to adults.

Most eggs are creamy-white in color, about 1/16-inch (1.5 mm) long, and are slight oval when first laid.

The larval stage causes the lawn damage. They have thick creamy-white bodies with brown head capsules. All species have three instars (the larvae molt three times).

The pupae start out cream-colored, then darken before the adults emerge.

The adults are typical scarabs—robust, oval beetles.

Grub Species

The most damaging grub species are:

Japanese beetle May or June beetles Northern masked chafers Southern masked chafers Black turfgrass ataenius

European chafer Asiatic garden beetle Green June beetle Oriental beetles

Damage

Grubworms eat organic matter, including the roots of plants. They find the roots of the grass in your yard very tasty.

The primary damage to your yard is drought stress. The secondary damage comes from predatory mammals, such as skunks, raccoons, opossums and moles, which dig under and through the turf in search of a white grub meal.

Acceptable Control Techniques

There are six different control methods you can use on white grubs.

• Cultural Control—Certain species of scarab adults prefer specific host plants. If you have problems with Japanese beetles, don't plant roses, grapes and lindens around high maintenance grass areas. May/June beetles prefer oaks. Green June beetle adults feed on ripening fruit, like peaches.
• Water Management—Most species require moist soil for their eggs to hatch. The young larvae are also very susceptible to drying out. Avoid overwatering your lawn. Let it dry out between waterings.
• Natural Control Parasites—Several parasitic wasps attack white grubs and may reduce populations in certain areas. However, these wasps may take two to three years to build up populations large enough to be effective.
• Biological Control—Parasitic beneficial nematodes from the genera Steinernema and Heterorhabtitis have been shown to be effective. These nematodes are sold commercially.
• Pheromone Control—researchers have identified pheromones for Japanese beetles and Oriental beetles. These pheromones can be used in traps to monitor adult activity similar to light trap monitoring.

• Beneficial Insect Control—by growing nectar and pollen plants, you can attract native beneficial insects, both predators and parasites.

  While cats, skunks, opossums, armadillos, raccoons, foxes, coyotes, and other animals feed on grubs, they'll dig up your lawn to do so. Leave them as a last resort.

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