JAPANESE BEETLE, a beetle (Popillia japonica) which was accidentally introduced into the United States probably in the larval form in earth around the roots of some plant imported from Japan. It was first discovered in the United States in 1916 near Riverton, N.J. Since that time it has spread to a number of other States. At the close of 1938, the area of continuous infestation covered about 15,000 sq.m. along the Atlantic seaboard, with scat tered infestations of varying intensity at other points from Maine to Georgia, and west to Missouri. In the older infested areas the infestation has diminished. The adult beetle feeds upon about 200 species of plants, including practically all the economic crops, seeming to prefer, however, apple, quince, peach fruit, cherry, plum, grape, blackberry, clover, and corn. It also attacks the foliage of many shade trees and ornamental shrubs ; also many weeds, especially smartweed (Polygonum sp). In many cases it completely defoliates trees and feeds upon the earlier-ripening varieties of fruits. The larva, living below the surface of the ground and feeding upon the roots of plants, damages lawns, pas tures, and golf courses, and also the roots of strawberries, cabbage, and other plants that have been set in heavily infested fields. The eggs are deposited in the soil, and hatch in about 14 days. The larva is one of the so-called white grubs, and passes its entire existence underground. The winter is passed in this stage, and during May it transforms to prepupa, and then to pupa, the adult beetle emerging from the middle of June to the end of July, the exact time depending on the locality.
The adult beetle is about 8 in. in length, and about the same in width. It is bright metallic-green in colour, with coppery brown wing covers. The beetles fly readily, feed avidly and lay eggs in late summer. There is only one generation each year, most of the year being spent in the soil as egg, larva, or pupa.
Federal and State agencies are making every possible effort to retard the spread of this pest to the areas uninfected. Measures have been developed whereby damage to individual properties may be very largely prevented. Several spray materials have been de veloped that are quite effective in preventing injury, if applied just as the beetles are beginning to appear on the trees and plants to be protected. Injury to lawns, golf courses, and other turf land may be prevented by treating the soil with lead arsenate.
Under the auspices of the U.S. Government, intensive studies of the Japanese beetle have been made in its original home. Sev eral species of parasitic wasps and flies have been found to destroy it there, and these have been imported into the United States. where several of them have become established. Certain diseases caused by bacteria, nematodes, and fungi have been found to be of importance in reducing the population of grubs in the soil.
The U.S. Department of Agriculture and several of the State Agricultural Experiment stations issue bulletins from time to time summarizing the results of investigational work. (L. 0. H.)