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How to Manage Pests

The UC Guide to Healthy Lawns

Masked chafers (white grubs) — Cyclocephala spp.

Masked chafer larvae

Masked chafer adults

Damage caused by masked chafer larvae

Larvae feeding under turfgrass

Click on images to enlarge.

Identification

Masked chafer adults are golden brown beetles, 3/4 inch (1.9 cm) long with dark brown heads. The adult beetle is hairy on the underside of its thorax. Larvae are white, C-shaped grubs with dark stripes on their backs and brown head capsules and legs. There is also a characteristic pattern of bristles on the underside of the posterior end of the abdomen. When full grown, white grubs are about 1 inch (2.5 cm) long, much bigger than ataenius or billbug grubs.

Hosts

All turfgrass species, especially annual bluegrass (a common weed in turf), Kentucky bluegrass, and perennial ryegrass

Damage

Masked chafer grubs feed on the roots of turfgrass. Damage appears in late summer or fall as irregular patches of brown, dying grass. The ground often feels spongy, and the lawn can be rolled up if heavily infested. Skunks, moles and birds may be attracted to lawns with high grub populations.

Monitoring information

Dig around the roots in damaged areas—especially in late fall through spring and look for whitish to yellow, wrinkled, C-shaped grubs. Look for yellowish-brown adults in the early to mid summer.

Management

Aerating the lawn can kill significant portions of white grub populations if they are feeding close to the soil surface. Follow recommended irrigation and fertilization practices. A healthy lawn can tolerate some grub damage. If more than 6 grubs are found per square foot, you may need to treat. Tiphiid wasps are common parasites of masked chafers but may not provide effective control. Beneficial nematodes may be effective if applied when grubs are young. Other insecticides are available including imidacloprid. Proper timing is essential.

Life cycle

For more information on lawn insects, refer to:
Pest Notes: Lawn Insects


Statewide IPM Program, Agriculture and Natural Resources, University of California
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