The adult Japanese beetle has a metallic green head and thorax and copper-colored wings with tufts of hair around the abdomen. Other beetle adults are a wide variety of colors from light to dark brown, to a wide variety of color patterns.

The grubs (larvae) are white in color with "C" shaped bodies, three pairs of legs, light brown heads and pronounced mandibles. Depending on the species, they range in size from 1/3 to 1-1/4 inches in length when fully grown. Grubs can be identified to species by examining the pattern formed by the spiny hairs on the underside of the tip of the abdomen. This area is referred to as the raster.

Biology. Many of the common species of white grubs in southern New England have a one-year life cycle. Other species, such as May or June beetles have a two-year life cycle. Beetles with a one-year life cycle deposit their eggs in the soil or thatch beginning in mid-summer (July). Eggs hatch beginning in early August and continue into September. Egg development is most successful in moist soil, such as on well irrigated turfgrass. Newly hatched larvae feed on the fine feeder roots of grasses. Older grubs may consume a majority of the plant's root system. Grub feeding continues throughout the fall. As soil temperatures cool in late fall, grubs migrate downward into the soil and hibernate for the winter. Once soil temperature reaches 50 degrees Fahrenheit, downward migration stops. The majority of grubs move downward a depth of 2 to 6 inches with fewer traveling 6 to 10 inches below the soil surface. In the spring, after frost disappears and soil temperatures begin to warm, grubs migrate upwards to the root zone. Larval activity can be seen as early as late March and continue through June. Grubs move slightly downwards in the soil to pupate. Depending on the species, beetles emerge from the soil in early June and continue through August. Adults are most numerous in July.

Damage. All turfgrasses present in New England serve as hosts for white grubs. Large areas of turfgrass can be killed and require extensive repair or renovation. Injury to turfgrass first appears as yellowing areas which quickly turn brown, especially during periods of high temperature and low rainfall. Badly damaged turfgrass can easily be rolled back like a carpet due to lack of roots. Injury often goes undetected during cool, moist weather. The majority of damage to turfgrass occurs in late summer and early fall.

Controls. Preventative versus curative controls. Grubs can be controlled using contact insecticides when feeding larvae are present in late August or early September. Contact insecticide available to use is Dylox (trichlorfon). A nonchemical alternative is the use of entomopathogenic (beneficial) nematodes. This biological control can be found under the name Steinernema carpocapsae and is available as Exhibit, BioSafe and BioVector. Heterorhabditis bacteriophora another beneficial nematode is also available. Beneficial nematodes work best on small, newly hatched grubs and should be applied accordingly in late summer (late August/early September) when newly hatched larvae are present.

Grubs that go untreated in late summer/early fall will reappear in spring. Contact chemical controls such as Dylox (trichlorfon) can be applied.

Preventative grub control can be obtained with one of two products; Mach 2® (halofenozide) or Merit® (imidacloprid)*. These products will not provide the intended results if applied at the incorrect time. Applications should be made prior to or during the egg laying stages of the adult beetles. For Connecticut Mid-June -- July applications work best.

Merit® is a systemic fungicide and translocates within the plant. As newly hatched grubs begin to feed on turfgrass roots, they will ingest the Merit® and die. Merit® has a broader spectrum of grub control than Mach II, but is not effective on caterpillars such as cutworms, armyworms or sod webworms.

Mach 2® (halofenozide) is in a new class of insecticides that works by mimicking growth hormones that accelerate the molting process between larval stages. Halofenozide has exhibited control of sod webworms, cutworms and armyworms. However, it is not as effective as Merit® in controlling the European Chafers or the Asiatic Garden Beetle.

In order to receive the benefit of full season long control as stated on the manufacturers label, applications of these products are required just prior to or during the egg laying stage of the adult beetle. When using these products and following the label for correct timing and application rates there should be no a need to apply another insecticide to achieve grub control until the following June or July. It is best to rotate the use of products from year to year to diminish the possibility of resistance.

All controls whether chemical or biological must be watered in with 1/2-1 inch of water immediately after application to be effective. If water cannot be applied to the area where grub control has been applied and rain is not in the forecast, do not apply anything. Water is necessary to wash the material through the thatch to the region where grubs are located.

Reasons for failure to control grubs. The most common reason grub control products fail to control grubs is that they are applied at the wrong time! Pesticides applied at incorrect times or without water, are a misuse of pesticides and a waste of time and money. Excessive thatch and microbial degradation can also account for failure when controlling white grubs on the home lawn.

* Imidacloprid is now the active ingredient in Grub X

By Dana Karpowich and Tim Abbey, University of Connecticut
Updated 6/10/04 by Steven L. Rackliffe, Extension Instructor Turfgrass Science, University of Connecticut

Also see
Controlling Insects and Common Pests of Lawns
Insects and Other Common Pests of Lawns

Information on our site was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.