FIG. 126.—Japanese beetles feeding on apple foliage
[Japanese beetles defoliating young 'Honeycrisp' trees in North Carolina -ASC]
Quarantine on Nursery Stock and Soil
JAPANESE Beetle Control
Since the Japanese beetle (Popillia japonica Newman) was found to occur in the United States, in 1916, at a point near Riverton, N. J., it has increased its numbers and area of distribution until at the close of the summer of 1926 it occupied an area of approximately 13,919 square miles. The States of New Jersey, Pennsylvania, and Delaware are cooperating with the Federal Government in supporting this project, and large appropriations are being made for the further study, control, and prevention of spread of this insect.
The Japanese beetle became established in a territory particularly suited to its requirements. Here were large areas of sod land where it could breed in almost unlimited numbers, together with a variety of crops and plants on which it could feed, in many cases without restriction. The temperature and moisture conditions were favorable for its development, and these, together with an almost total absence of parasitic or predacious insect enemies, have enabled it to reproduce and multiply in unbelievable numbers. The density of infestation in the vicinity of Riverton, N. J., where the beetle has occurred for the longest time, has increased from year to year. This increase was marked by corresponding increase in damage to various crops, such as apples, peaches, cherries, grapes, and ornamental plants. It is only within the last year that the density of infestation apparently has reached its maximum.
The color of the Japanese beetle is bright metallic: green, except the greater part of the wing covers which are coppery brown. The wing covers do not entirely hide the abdomen, and expose a row of five lateral and two posterior spots composed of white hairs. The under surface of the body is covered with short grayish hairs; the legs are dark metallic green, varying in tint in different positions. The adult beetles are about one-half inch long. The Japanese beetle has an annual life cycle. The adults begin to emerge between the 10th and 15th of June and are present until the middle of October. Each adult female beetle lays between 40 and 50 eggs in the soil. These are deposited at various times, usually at the rate of 3 to 5 eggs per day during a period of four or five weeks. When hatched the tiny grubs are about one-sixteenth inch long. They become full grown in about six weeks, at which time they reach a length of approximately 1 inch. The larvee resemble our native white grubs in appearance, although they are considerably smaller than the larve of the common June beetle. As cold weather approaches in the fall they enter the soil to an average depth of about 7 inches, where they pass the winter in a quiescent condition. In the spring the larvee become active again and move upward near the surface of the soil, where they feed for about a month, and by the latter part of May or early June transform to pupe, and appear as adults two to four weeks later.
Over 200 species of plants have been recorded as furnishing food for the Japanese beetle in New Jersey. Practically all of the economic crops grown in the infested territory are represented in the list. The more favored food plants include apple, sweet cherry, plum, grape, blackberry, clover, soy bean, and corn; shade trees, including linden, birch, elm, horse-chestnut, sassafras, willow, white oak; and many ornamental shrubs, particularly althea and rose. Flowering plants and weeds of many kinds are also attacked. Besides attacking the foliage (fig. 126), the adult Japanese beetles are especially partial to the fruit and are often found clustered on both apples and peaches in large numbers (fig. 127). As many as 278 beetles have been collected at one time on a single apple. The feeding is characteristic and resembles that done by the native rose chafers.
When abundant, the larvæ or grubs of the Japanese beetle have become a serious pest in lawns, golf courses, and pastures. The rich soil in the heavy turf of golf courses has offered attractive places for the beetles to lay their eggs. The larvæ feed on the grass roots, cutting them off immediately below the surface of the ground.
The quarantine on farm products is intended to prevent the carrying of the adult beetle from the infested area to points outside on such articles as experience has shown as likely to harbor the adult beetle. At the present time the movement of the following articles is restricted: Sweet corn, beans or peas in the pod, cabbage, parsley, carrots with tops, beets with tops, onions with tops, lettuce, outdoor-grown flowers, hay, straw, unthreshed grain, and forage crops. The restrictions on these articles are effective during the time the beetles are on the wing; namely, between June 15 and October 15.
The quarantine on nursery stock and soil is to prevent the carriage of any of the immature stages of the Japanese beetle to points outside the infested area. Since one or more of the immature stages are to be found in soil at all times, the regulations affecting the shipment of sand, soil, earth, peat, compost, and manure are effective throughout the year.
The absence of any natural or parasitic enemies of the Japanese beetle became apparent soon after its discovery in New Jersey. Therefore, two experts were sent to Japan in 1920 for the purpose of studying the insect in its native home and of finding, rearing, and shipping to this country any of its natural enemies which seemed desirable.
Large shipments of parasites have been received from Japan, many of which have been reared and released in the heavily infested area near Riverton and Moorestown, N. J. During the summer of 1924 the tachinid fly Centeter cinerea, which lays its eggs on the adult beetle and kills it within about five days, was found to be established near Moorestown. In 1925, during the first two weeks of beetle emergence, an average of 8 per cent of the beetles were parasitized by the Centeter, and before the end of the season it was found that the parasite had extended its range to include approximately 40 square miles. A large number of dexiid flies of the species Prosena siberita have been imported and released in the Moorestown district, and likewise a large number of solitary wasps of the genus Tiphia have been imported.
A method has been developed for the control of the larvæ in lawns, contemplating the use of a 71 per cent emulsion of carbon disulphide diluted at the rate of 1 quart of concentrated emulsion to 50 gallons of water. The dilute emulsion is applied to the sod at the rate of 2 or 3 pints to the square foot.
As the beetles became more numerous the usual sprays applied for the control of many of our native pests were not effective. Therefore, a large amount of work and study has been devoted to the working out of measures whereby apples, peaches, grapes, and ornamental plants could be protected from their attacks.
On ornamental plants, the best control was obtained with a spray consisting of a mixture of lead arsenate and lead oleate, at the rate of 4 pounds of the paste to 50 gallons of water. A mixture of lead arsenate and flour, used at the rate of 3 pounds of lead arsenate and 2 pounds of flour to 50 gallons of water, gives good control on apples cherries, grapes, and plums. It was found that lime gave very good protection as long as it remained on the foliage or fruit. However, lime does not have good sticking qualities and is easily washed off by rains. [Note that lead compounds are no longer recommended due to their persistence in the environment and permanent damaging effects on human health. For modern methods of controlling Japanese beetles, consult your county Agricultural Extension agent. Some tips can be found here as well. -ASC]
It is anticipated that a pyrethrum soap developed at the laboratory may be extremely useful for the householder who wishes to destroy the beetles on rose bushes and other flowering plants. Additional investigational work is continuing along the lines of developing a substitute for arsenate of lead which can be used in obtaining effective control of the Japanese beetle. Several materials have been developed which are showing promise, although it is not expected that they can be recommended until much further work has been done.