ANR-177, Reprinted May 1998. Patricia P. Cobb, Extension Entomologist, Professor, Entomology, Auburn University

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Controlling White Grubs On Lawns And Turf

White grubs in soil.	Green June beetle.
	White grubs are immature (larval) stages of June or May beetles. Most grubs mature in a year; others take 2 or 3 years. Grubs damage lawns and turf by feeding on grass roots. Dead or dying patches of grass in spring or fall may be the result of grubs feeding on roots. Moles digging into lawns or flocks of birds feeding on lawns sometimes indicate the presence of grubs. Most lawn grasses are subject to attack by white grubs.

Hard-shelled, brown May or green June beetles emerge primarily from April through June in Alabama, mate, and lay eggs. The grubs soon hatch and begin feeding on grass roots. These smaller grubs are easier to kill with chemicals than when they are larger. This is why treatment in mid-summer or early fall (late July through September) is usually more effective than at other times; most larvae have hatched by this time and are still small. Grubs overwinter deep in the soil and move up the following spring. If they are a "one-year" species, they pupate, and adults emerge that same year. Treatment in damaged areas in late March to mid-April may kill larvae before they pupate, but treatment of smaller grubs is most effective and preferred.

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Description

White grubs (Order Coleoptera, Family Scarabaeidae) are 1/2 to 1-1/2 inches long, have three pairs of legs near the head, and characteristically rest in a C-shaped posi-tion. Their heads and rear ends are brown. Green June beetle grubs crawl on their backs with their legs up. Grubs can be identified by the pattern of spines (rasters) on the rear ends. It is important to know the kind of grub in order to know when to treat.

Damage

Grubs damage turf by eating grass roots. Damaged patches of grass feel loose and sometimes can be rolled up like a carpet. But, when the grass is growing rapidly in the summer and is not suffering from drought, infested areas may remain green on top even though the roots are eaten away. These areas do not "green up" in the spring.

Don't guess about grub damage and treatment! Some-times damage from cold, drought, nematodes, or main-tenance practices resembles grub damage. Use a knife or spade to cut several 1-foot square samples, 3 inches deep, from the edge of the damaged areas. Fold the sample back and examine the soil for grubs. Treatment is often required when an average of three to five grubs is found per square foot. Replace the sod carefully and pack it into place. Beetles may reinfest the same areas year after year. Most new generation grubs in Alabama are present in the soil by mid-August and are easier to control at this time because they are smaller.

Control

Be sure to sample for grubs before treating. On large, commercial turf areas such as golf courses, sod farms, and commercial landscapes, grub infestations can be "mapped." Map areas by sampling extensively with a greens cup cutter. Record on a map the presence or absence of grubs in each sample plug. Treating only mapped areas of grub presence reduces the area treated and, therefore, the amount of pesticide used.

Water grass before treatment if the soil is dry unless prohibited by label. When dry soil conditions exist, watering before treatment causes grubs to move nearer the soil surface. Water thoroughly again after treatment is applied.

Japanese beetles. Milky spore products (containing bacteria which infect only Japanese beetle grubs) have produced limited success in controlling grubs in Alabama. Milky spore bacteria at best work only on Japanese beetle grubs to suppress populations over time.

Insecticide control of Japanese beetle adults is difficult because of their mobility. Spray formulations of carbaryl (such as Sevin) that are registered for site use are recommended for homeowners and commercial applicators.

Hand collecting beetles may not be the most effective method of control but can be used in areas where beetles are less numerous. Japanese beetles are pests in parts of northern and east central Alabama. Japanese beetle adult flights peak most years in June.

Japanese beetle traps in home landscapes may do more harm than good. Beetle presence on plants attracts more beetles. Beetles that are attracted into the area may not make it to traps. Planting less susceptible plants, such as boxwood, dogwood, holly, or lilac, may be an alternative.

Precautions

DO NOT use pesticides on plants other than those listed on the label. Site and/or use directions may change. ALWAYS FOLLOW LABEL DIRECTIONS.

Key: EC = emulsifiable concentrate; G = granular; S = sprayable; WP = wettable powder.

The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection Agency and the Alabama Department of Agriculture and Industries. If a registration is changed or cancelled, the rate listed here is no longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest information.

Trade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or guarantee any product and does not recommend one product instead of another that might be similar.