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Nematode Parasites of the Japanese Beetle

In 1929, while investigating Japanese beetle grub mortality, R. W. Glaser and Henry Fox found many grubs on the Tavistock golf course near Haddonfield, New Jersey, that were parasitized by a nematode or round worm. Later this nematode was characterized as a parasitic form and named Neoaplectana glaseri by G. Steiner, nematological specialist of the United States Department of Agriculture. In view of the possibilities in culturing and disseminating large numbers of this parasitic enemy of the Japanese beetle in New Jersey, Glaser, a parasitologist of the Rockefeller Institute for Medical Research at Princeton, New Jersey, was retained by the department as consultant and immediately began work on the artificial culture of the nematode. At first this seemed hopeless because no parasitic nematode of any sort had previously reproduced in artificial media in spite of many attempts by parasitologists. However, after much preliminary work Glaser was successful in culturing the nematode. Then many laboratory and field experiments were made to determine dosages, survival, extent of parasitism, etc.

Experimental work was continued from 1931 to 1938, for many practical difficulties had to be resolved before a colonization program could be developed. Various methods of introduction, such as a water suspension of the nemas, burying small samples of culture every few yards, and spraying the nemas on the soil surface, were tried. In September, 1933, one of the rooms of the Japanese beetle suppression project headquarters at Elmer, New Jersey, was converted into an incubation room. After experiencing difficulties with temperatures, the work was postponed and, in the spring of 1934, the equipment moved to one of the state buildings at White Horse, New Jersey.

In 1935 field experiments were continued and the nemas were introduced at ten places in the state and parasitized grubs were recovered later from the treated areas. During the year, 25 million nematodes were produced and put out, some being incorporated in soil at the laboratory before being distributed in the field. During 1936 subsurface applications were made in 41 fields involving an area of 1.5 million square feet. Although it was difficult to arrive at exact percentages of parasitism due to the disintegration of grubs, sizable declines in the grub population were noted in treated fields.

A state-wide colonization program was started in 1940 and at the same time, through the cooperation of the Federal Japanese Beetle Laboratory at Moorestown, New Jersey, colonies of the bacterial disease known as Type A, milky disease were introduced. In 15 counties, 319 colonies were introduced at 3.5-mile intervals. By 1941, colonization was complete with the establishment of 172 additional colonies. The number of sites required at 3.5-mile intervals was 603. In 1938 preliminary experiments were tried with the use of nemas against the white-fringed beetle, and during 1941-1942 hundreds of millions of nematodes were cultured and sent to Gulfport, Mississippi, for laboratory and field tests by government men. From 1932 on Ellis E. McCoy has had charge of the parasite laboratory.