Nematology in the United States

This document was constructed and is maintained by KHUONG B. NGUYEN
Entomology and Nematology Department
University of Florida

                Joseph Leidy reported our first record of free-living nematodes in America.
           The three globular supplements of the male indicate that this species was a Trilobus (now Tobrilus), and it was from this information that Cobb (1914) redescribed and Chambers illustrated T. longus (Leidy) from specimens collected in the same general locality.  In this work Leidy also described AnguillulaLongicauda n.s. and AnguillulaFossolarius n.s., neither of which is recognizable.

           As might be expected, root-knot nematodes, Meloidogyne spp., were the first plant parasitic species observed in the United States, and these were recorded by May in 1888. Working independently, Atkinson in Alabama and Neal in Florida made extensive researches in the morphology, host ranges, and crop damage of these pests, and in 1889 both published the results of their investigations. Halstead in New Jersey (1891) and Stone and Smith in Massachusetts (1898) published additional observations, and from that time on numerous workers recorded the results of their research and observations.

            An important event in the development of nematology occurred in 1907, when N. A. Cobb joined the U.S. Department of Agriculture. Cobb had secured his doctorate at Jena in 1889, after which he worked in Italy for a short time. Here he collected nematodes, some of which he mounted in balsam; so expertly were the slides made that the specimens are still in excellent condition. He then proceeded to Australia, but failing to find professional employment he sold watches until an opening was available in the New South Wales Department of Agriculture. His first paper on plant parasitic nematodes, "Tylenchus and Root Galls," appeared in the Agricultural Gazette of New South Wales (1890). Apparently, at that time he did not know that the names Heterodera and Meloidogyne had already been proposed for the gall-forming nematodes

         About 10 years later he became associated with the Experiment Station of the Hawaiian Sugar Planters Association, where he investigated the nematodes found in sugar cane fields. Here he began developing equipment for microscopy, fitting the windows with special shades and reflectors to control lighting while working over the microscope and making camera lucida drawings. Much of this equipment is still preserved at the station.

        His first assignment in the U.S. Department of Agriculture was the standardization of cotton grades, which were published in 1907. About 1910 he succeeded in transferring his attention to nematodes. His first paper, "New Nematode Genera Found Inhabiting Fresh-water and Non-brackish Soils," was published in 1913. From that time on, a long series of important papers came from his versatile pen. Among his writings Contributions to a Science of Nematology is the most outstanding. It was Cobb who proposed that plant parasitic and free-living nematodes be removed from helminthology and be assigned to a new branch of science to be known as "nematology." He also proposed that "nema" be substituted for "nematode," and it is most unfortunate that this suggestion has not met with general acceptance. His ingenious nature was then directed to the development of equipment and techniques necessary to separate nematodes from soil and prepare them for microscopic study. His laboratory manual "Estimating the Nema Population of Soil" (1918) formed the basis for a large portion of the methods and apparatus used in nematology today.

       Studies on the minute morphological details of plant parasitic nematodes occupied much of his time, with special reference to those organs which he named "amphids," "phasmids," and "deirids." To secure a better perspective on their morphology, he studied the large marine species, on which details were much more easily observed, and for this purpose he spent several summers at the Bureau of Fisheries Station at Woods Hole, Massachusetts. Those who were fortunate enough to be included on these expeditions will ever remember those halcyon days of nematology.

       Cobb's interests were not confined to nematology and microscopy but extended to photography of birds and insects and the development of special equipment for photomicrography and other microscopic work, , such as the installation of heavy pipes filled with concrete to reduce vibration during such work. Often these devices resulted in weird and complicated assemblies, for he seemed to lack the ability to simplify either apparatus or procedures. His laboratories were always a show place of revolving tables with several microscopes on each and special devices to perform laboratory techniques. Probably his most useful invention was the metal microscopic slide, which many of us prefer to the conventional glass type. Another important contribution was the use of a simple beam splitter and large mirror to replace the old-type camera lucida.

       His genial and humorous nature will ever be remembered, especially by those who were present at a certain meeting of the Helminthological Society of Washington. He appeared with numerous boxes and cartons which contained "A Collection of Holes," which he had assembled during his travels, and on them he proceeded to deliver a solemn and profound dissertation which rocked the audience with laughter. This was probably a satire on certain members of the society who always had entirely too much to say about things of which they knew little or nothing. His sudden death at the age of seventy-three terminated all too soon an important period in the development of the science of nematology. No other individual has had a more profound and permanent influence on the profession than N. A. Cobb.

      Associated with Cobb during those early eventful years was W. E. Chambers, artist and microscopist. From his gifted hands nematology received the finest illustrations of nematodes that have ever been made, and it is doubtful that they will ever again be equaled. Cobb's microscopic ability and unusual ingenuity, coupled with the artistry of Ghambers, established a new era in nematology on which our present science is largely founded, not only in America but in all parts of the world. Among the early contemporaries of Cobb in the U.S. Department of Agriculture we find Ernst A. Bessey, soon after the turn of the century, working on root-knot nematodes. His report (1911) included a review of the principal work done up to that time and included considerable original research. This paper still remains one of the outstanding contributions to our information on this group.

       E. G. Titus observed sugar beet nematodes in a field near Lehi, Utah, in 1907 and reported his findings to the U.S. Department of Agriculture. A few years later Harry B. Shaw was assigned to make a survey of the distribution of the pest. His report (1915) included an excellent sum mary of the voluminous European literature and remains one of the outstanding publications on this subject. In 1918 Titus was responsible for initiating the sugar beet nematode project in the U.S. Department of Agriculture. The writer is deeply indebted to him for the opportunity to head the work which eventually developed into the first permanent nematology field station in the United States, located at Salt Lake City, Utah. Studies were extended to many phases of nematology, with special emphasis on assembling a taxonomic collection which eventually reached over thirty-six thousand indexed specimens representing upward of two thousand species. Based on this collection, monographs y were compiled for over sixty genera, and numerous other papers were issued. The collection attracted many visitors both from home and abroad who found it a valuable source of reference in studying rare and little-known genera and species. The specimens are still available to qualified and responsible persons engaged in assembling monographs on various groups. W. D. Courtney, C. W. McBeth, M. W. Allen, H. W. Reynolds, and other young nematologists of the Western states received much of their training at this station. Allen has carried on the tradition in the Nematology Department of the University of California, Berkeley, where he has trained several of the world's outstanding younger nematologists.

      Other members of the U.S. Department of Agriculture who were associated with Cobb were J. R. Christie, G. Steiner, B. G. and M. B. Chitwood, A. L. Taylor, Helen Heinley Swanger, Edna M. Buhrer, Grace Sherman Cobb, Louise Crossman, Josephine Danforth, Florence E. Albin, Margaret N. Corder, Cevilla Brooks, and numerous others who aided with laboratory and office work for shorter periods of service.

       A considerable number of other workers in the United States made valuable contributions on nematological problems during this time. Among them were L. P. Byars, D. G. Milbrath, G. H. Godfrey, R. W. Leukel, M. B. Linford, J. R. Watson, and A. G. Newhall.

        Perhaps the most important index to species of nematodes is that of Stiles and Hassall, which was issued in 1920 under the title "Index Catalog of Medical and Veterinary Zoology. Roundworms." Fortunately, the authors included practically all the citations to plant-infesting and free-living nematodes that had been published up to that time. This compilation is a boon to anyone searching for references to early works on nematology.

        Following Cobb in 1932, G. Steiner directed the work of what is now known as the Nematology Section of the U.S. Department of Agriculture. His first work on nematodes had been done in Switzerland, his native land, but in 1921 he came to Yale University for a year of study and accepted a position under Cobb in 1922. His work was divided between plant and insect parasitic nematodes and fresh-water and marine forms. His contributions cover a wide range of subjects and total about two hundred at the present time (1959). Working with Cobb, he collaborated on morphological and taxonomic problems which added many interesting items to our knowledge.

        Funds for expanding research were increased about 1940, and several new projects were initiated in the Eastern and Southern states. Personnel of the Nematology Section increased until about thirty are now employed. Encouraged by this recognition of the importance of nematology, state experiment stations, plant inspection services, and, industry have added nematologists to their staffs. There are now about one hundred workers engaged on a wide variety of nematological projects located throughout the country.

        Many workers were trained in the Beltsville, Maryland, laboratories, and numerous visitors from home and abroad received instruction while assigned there for various lengths of time. Two of the most important persons in this training program were Edna M. Buhrer and Grace S. Cobb.

         At the time of his retirement in 1956, Steiner was presented with the Distinguished Service Medal of the U.S. Department of Agriculture and soon afterward accepted a position with the government of Puerto Rico.

        A. L. Taylor succeeded Steiner after spending twenty years in the Nematology Section in field stations of the Southeastern states and as assistant in the Beltsville office and laboratory. His long and successful career in practical field nematology and administrative training augurs well for the future of nematology in this country. One of the finest achievements of this period was that of working out the life histories and economic importance of two mermithid parasites of grasshoppers in the northeastern United States. This was done by J. R. Christie, working in collaboration with N. A. Cobb and G. Steiner. Their papers on Mermis subnigrescens and Agamermis decaudata will always remain as classics in this branch of nematology. As a perfectionist, Christie is without a peer among the nematologists of the world, and his papers, while not numerous, are all outstanding contributions to the science.

       The story of nematology in America would not be complete without a tribute to A. D. Baker, Wm. Newton, R. J. Hastings, and J. E. Bosher of Canada. Working largely by themselves, in isolated stations, they have produced some of our best studies on stem, root lesion, potato rot, and other plant parasitic nematodes. Among the outstanding works published during these years is An Introduction to Nematology by B. G. and M. B. Chitwood. This ap-proaches the subject of nematology from a purely zoological standpoint and covers the entire Phylum Nemata. Detailed morphological studies of the supergeneric groups are presented, with a lavish use of figures illustrating the principal diagnostic characters of each. Discussions and comparisons are made largely on a family basis, with occasional figures setting forth the characters of genera or species representative of the higher groups. The work is especially valuable for the advanced student in nematology. However, the beginner will find much of interest in the historical and general discussions and in the great variety of morphological structures illustrated. An excellent book "Plant Nematodes, Their Bionomics and Control, has recently been published by J. R. Christie (1959). Discussions are presented of all plant parasitic nematodes, either individually or in generic groups. Special attention is given to symptoms, life history, feeding habits, distribution, and control. Research workers in agriculture, teachers, students, plant inspectors, county agents, and other workers in agriculture will find a wealth of information presented in simple, direct language.