The Regional Review

Volume I - No. 2

August, 1938


By Fred H. Arnold,
Regional Forester.

In common with most of the destructive tree insect pests in the United States the Japanese beetle is of exotic orgin. Its native home is Japan, hence the name by which it is commonly known. Entomologists speak of this "bug" as Popillia Japonica. First discovered in this country near Riverton, N. J., in 1916, it since has thrived and spread throughout southern and central New Jersey, eastern Pennsylvania, and northern Delaware. Beyond this area the beetles have been found from New England to South Carolina and as far west as Missouri. Despite strict quarantine regulations enforced by the U. S. Department of Agriculture and other efforts to check it, the beetle appears to be increasing gradually in numbers and widening its geographical distribution.

There are four stages in the life history of this destructive pest, namely; the adult (beetle), egg, larva (grub), and pupa. Anyone who has seen the adult beetle will not soon forget its striking appearance. It has a lustrous metallic green color with a bronze sheen on the wing covers. Broadly oval in shape it is slightly less than one-half inch long and one-fourth inch wide. The eggs are between one-sixteenth and one-eighth inch long, elliptical to nearly spherical, and of a creamy white color. The typically curled larva varies in length up to an inch, with a white body that is bluish within, and with a light brown head. About the size of the adult and resembling it somewhat, the fully developed pupa is tan in color and elliptically shaped.

beetle life stages

Depending upon the advance of the spring season and varying with latitude and elevation, the adult beetles emerge from the soil during June and July. Immediately they begin to feed upon plant leaves and flowers, having voracious appetites. They habitually mass themselves in dense clusters on certain individual plants which are thus heavily fed upon, while seemingly ignoring other nearby plants of the same kind. As many as 296 beetles have been found massed upon a single apple. The adults are short-lived, averaging one month to a month and a half of life as herbivorous gourmands. They feed and fly about most vigorously on warm, sunny days and similarly during the warmer part of the day, between 10 A.M. and 3 P.M. Early in the morning and late in the afternoon they feed on the lower plants, and during the middle of the day when they are most active they are likely to be found seeking food on the higher trees. The beetles are relatively in active on cloudy or cool days. By late August most of the adults have dies, their bodies lying on the ground beneath the badly mutilated host plants. Late individuals occasionally may be found flying about until October since all do not leave the soil at the same time.

Egg-laying begins soon after emergence, the females burrowing a few inches into the soil and depositing one to four eggs at a time. Another group of eggs may be laid after a day or two of feeding, and this program is repeated until mid-August by which time each female has deposited between 40 and 60 eggs. Both male and female beetles continue to feed ravenously from the time of their emergence until death.

The eggs require only about two weeks to hatch after they are laid. The resultant grubs feed upon the finer roots in the soil, particularly those of grasses, legumes, and of certain flowers and garden vegetables. Extensive patches of lawns may be killed as a result of this injury. During this feeding period the larvae work within the upper three inches of the soil, but with the approach of winter they burrow deeper and spend the winter in an inactive state at depths of from four to eight inches below the surface. With the rising of soil temperatures in the spring the larvae move upward and again feed on roots between April and June. During May or June they are transformed to the pupal stage which is a dormant condition lasting from one to three weeks depending upon the climate and other local conditions. Pupae then are transformed into adult beetles which in turn emerge from the soil and the life cycle is thus complete.

The Japanese beetle is known to feed upon a great variety of plants. Nearly 300 different species of non-evergreen trees, shrubs, and flowers are eaten by the adult beetles with varying degrees of preference. Certain species, such as apple peach, plum, cherry, grape, rose, elm, horse chestnut, sassafras, willow, basswood, raspberry, blueberry, dahlia, hibiscus, hollyhock, and zinnia, are highly susceptible to attack by the insect and are heavily damaged by it. Other plants, however, are relatively resistant to it and are only seldom attacked. Some of these more or less immune plants are evergreens, including rhododendron and azalea, ash, beech, most of the oaks and maples, honeysuckle, redbud hydrangea, lilac, privet, forsythia, peony, petunia, tulip, gladiolus, and phlox. The beetles usually feed upon the tender tissue between the veins of the leaves, thereby skeletonizing patches of or the entire leaves, and leaving only the ribs and veins. Blossoms and fruits also are consumed. Flowers, shrubs, and, in cases of severe in festations, even large shade trees, may be defoliated completely.

(Reproduced from U.S.D.A. Circular No. 332)
(click on image for an enlargement in a new window)

Several outbreaks of this pest now occur in National Park and Monument areas in Region One. At George Washington Birthplace National Monument, in Westmoreland County, Va., a heavy infestation has become established National Capital Parks, Washington, D. C., have a Japanese beetle problem. A vigorous attack was recently reported at Fort McHenry National Park, Baltimore, Md. Morristown National Historical Perk Morristown, N. J., is troubled with the pest, and the famous Statue of Liberty National Monument on Bedloe's Island, N. Y., also is host to the insect.

The Japanese beetle is now so widely and heavily distributed that its complete eradication is beyond practical means of accomplishment. Its spread may be checked and its numbers and the amount of damage reduced, however, by energetic and intelligent application of various control measures that are known at present. These measures are briefly as follows:

1. Spraying the soil in infested areas with lead arsenate to poison the grubs.

2. Spraying infested plants with a poison, such as pyrethrum, which kills by contact with the insect.

3. Strict enforcement of state and Federal quarantine regulations restricting the transportation of soil, potted plants, nursery stock, and other plant material.

4. Trapping with specially designed beetle traps.

5. Hand collection before and during egg laying.

6. Introduction and encouragement of natural control agencies, such as parasitic insect enemies, birds, and other animal predators of both adults and larvae.

7. Planting species which are not susceptible to attack.

8. In the yard and garden, valued plants may be protected against damage by spraying them with a repellant such as aluminum sulfate. Lead arsenate is a stomach poison as well as a repellant but it destroys flowers, young leaves and other tender plant tissues.

From all outward indications this foreign beetle is here to stay; its ravages will vary in intensity from year to year depending up on climatic and other factors; it will exact an annual toll in destruction of vegetation; and our hope should be, through the application and encouragement of natural and artificial controls,to keep down the peak epidemics, thereby leveling off the curve of annual losses.


United States Department of Agriculture Circular No. 332, December, 1934, General Information about the Japanese Beetle in the United States, by C. H. Hadley and I. M. Hawley.

United States Department of Agriculture Circular No. 237, Revised July, 1936, Control of the Japanese Beetle on Fruit and Shade Trees, by W. E. Fleming and F. W. Metzger.

United States Department of Agriculture Circular No. 401, September 1936, Control of the Japanese Beetle and its Grub in Home Yards, by W. E. Fleming and F. W. Metzger.

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Date: 04-Jul-2002