WHITE GRUBS

Text adapted from Turfgrass Pest Management: A guide to Major Turfgrass Pests in Oklahoma
Oklahoma Cooperative Extension Service

INSECT AND DESCRIPTION: White grubs, Cyclocephala and Phyllophaga spp. Larvae or grubs about 1 to 1 1/2 inches long when fully grown, C-shaped when at rest with many folds or wrinkles in front half of body. Rear end of body often slightly larger in diameter than rest and may be bluish or blackish in color. White grubs have a brown head capsule and three pair of conspicuous legs. (Grubs of the billbug are legless.) Adults of white grubs are commonly called May beetles, June beetles, or June bugs. They are a little over one-half inch long and yellowish-brown with a reddish head.

LIFE HISTORY AND HABITS: The common species of Cyclocephala attacking turf in Oklahoma have a one-year life cycle while most of the Phyllophaga spp. have two year life cycles. Few recordings of 3 year life cycle grubs have been made in Oklahoma. The larvae approach maturity about October. The adult Phyllophaga's emerge from the ground from April to August depending on species. The adults of the annual's emerge from the soil from June through July. Little feeding appears to take place during the winter or early spring.


SUSCEPTIBLE PLANTS: All grasses.

DAMAGE CAUSED: White grubs feed beneath the soil surface on the roots of grasses. Above-ground symptoms are a browning and dying of the grass in localized spots or in large irregular shaped areas. Where infestations are heavy, the grass roots may be entirely eaten away as well as the grass blades and the turf may be rolled back like a carpet. Damage may be severe in September and October when the grubs are reaching maturity and the growth of bermudagrass is slowing down.

METHOD OF DETECTION: Examine the soil around the grass roots. Dig in brown areas near the edge of green, healthy areas of grass. If more than 1 grub per square foot of area is found the lawn should be treated. If the soil is dry, you may need to dig 6 to 10 inches deep to find larvae.

Photographs
Figure 1 -- "White grub", Courtesy of D. Bishop, University of Nebraska

Figure 2. -- "Annual white grub (Cyclocephala sp.)", Oklahoma Cooperative Extension Service