What are Nematodes? Nematodes are a diverse group of roundworms that occur worldwide in virtually every environment. Nematodes are second only to insects in the number of species in the animal kingdom. However, only about 3 percent of all nematode species have been studied and identified. One cubic foot of soil may contain millions of individual nematodes belonging to several different taxonomic groups.
Some of the best known nematodes are animal parasites such as heartworms, pinworms, and hookworms. Another important group of nematodes parasitize plants, which results in an estimated $8 billion a year loss to U.S. agriculture, and nearly $78 billion loss worldwide. Often, plant damage caused by nematodes is overlooked because the resulting nonspecific symptoms, such as slow growth, stunting, and yellowing, can also be attributed to nutritional and water-associated disorders.
Many nematode species are beneficial to agricluture and the environment. For example, some have proven to be important allies in the biological control of insects and other pests, and some contribute to soil fertility by helping cycle nutrients through the soil.
Nematologists, scientists who study nematodes, understand the critical need to develop ecologically sound and sustainable farming practices that protect soil, water, and human health. Nematologists at many different research institutions across the U.S., including the University of Florida, North Carolina State University, University of Georgia, Iowa State University, Michigan State University, and others, are working to establish a strong scientific foundation in nematode biology and management. The Society of Nematologists is a national scientific organization that fosters communication among nematologists. The remainder of this document provides a short history of nematology in the U.S., but emphasizes the development of nematology in California.
Nematology in California The Early Years: 1900-1940
In the early years, nematological research in the United States consisted of limited research on the root-knot nematodes. By 1907, a botanist and plant pathologist, N. A. Cobb (left, in his later years), was employed by the USDA, and he initiated studies with nematodes which resulted in a prolific record of publications describing and identifying a wide array of nematode species. He assembled a productive research group in Washington D. C. which established nematology as a new field in agricultural and biological research. In 1911, one of this group, E. A. Bessey, first reported the occurrence of root-knot and sugar beet cyst nematodes in California.
Another nematologist from this group who was stationed in Utah, Gerald Thorne (left), conducted research in California on the sugarbeet cyst nematode. Thorne described other nematodes from California. Another member of the group, D. G. Milbrath, became the first chief of the Bureau of Plant Pathology of the California Department of Agriculture. Perhaps as a result of his interests, the citrus nematode was discovered by a Los Angeles County Agricultural Inspector, and was identified and described by N. A. Cobb in 1913. From this followed observations by E. E. Thomas of the Citrus Experiment Station in Riverside in 1923 that the same nematode was able to injure citrus seedlings grown under controlled conditions. During this time, the stem and bulb nematode was recognized in California and in the late 1920's root lesion nematodes were observed to attack fig roots and subsequently, apple roots in 1938. In the 1920's and 1930's there arose a gradual awareness of the incidence of nematodes on plants, and county horticultural commissioners were increasingly condemning nursery stocks showing root-knot nematode symptoms. In 1925, Milbrath provided one of the early estimates of biological loss caused by root-knot nematodes, suggesting that 5% in tomatoes, 2% in beans and sugar beets, and 0.5% in grapes were lost due to nematode parasitism. He specifically suggested that 5% of garlic production was lost due to damage caused by the stem and bulb nematode, and that 5% of sugarbeet production was lost due to the sugarbeet cyst nematode.
In 1933, Jocelyn Tyler of the Department of Entomology and Parasitology at the University of California at Berkeley made what is now considered a classic contribution to the study of root-knot nematode biology by establishing the relationship between nematode development and temperature. She demonstrated that reproduction without males was common in root-knot nematodes, and that this reproduction could persist for at least 12 generations without males. During this period several plant pathologists made important observations on root-knot and stem and bulb nematodes in California.
The Mid-Century: 1940-1985
In 1943, M. W. Allen initiated nematology research in the Department of Entomology and Parasitology at the University of California at Berkeley. In 1947 at UC Berkeley, Professor Allen taught the first formal nematology course ever offered at a University. In the same year, R. C. Baines initiated nematology research after joining the Department of Plant Pathology at the U.C. Riverside. In 1948 D. J. Raski joined the nematology program in the Department of Entomology and Parasitology at UC Berkeley.
During the mid-1900s the agro-industrial community became more aware of the importance of plant-parasitic nematodes. The more outspoken leaders of this awakening were J. E. Armstrong (a Tulare County rancher), D. G. Milbrath (of the California Department of Agriculture), and C. E. scott and H. F. Smith (of the UC). In 1951, hearings were held by the Joint Legislature Committee on Agriculture and Livestock. The Department of Agriculture and the UC participated in the hearings, and reviewed the status of nematode problems. The hearings led to a recommendation for increased research on nematode problems. The same year, the California Department of Agriculture selected W. H. Hart as the first nematologist for the Bureau of Plant Pathology. The next year, the agriculture committee of the California State Chamber of Commerce appointed a nematode study committee led by J. E. Armstrong. The committee recommended that nematology be treated as an independent science in the UC, and that an increase in support funds be made available for research, staff, and facilities.
The recommendations of the State Chamber of Commerce which had been accepted by the legislature and the University of California were implemented in 1953. D. J. Raski was transferred to the Department of Entomology at the UC, Davis, and by early 1954 B. L. Lear and B. F. Lownsbery had arrived. Meanwhile, S. A. Sher joined the Department of Plant Pathology at the UC, Riverside.
In 1954, the Statewide Department of Plant Nematology was established with D. J. Raski (at left, Viglierchio (left) and Raski (right)) as the Chairman, and M. W. Allen (UCB), and R. C. Baines (UCR) as Vice-Chairs. By this action, the University of California became the first academic institution to recognize Nematology as a field of science separate from Plant Pathology, Entomology, or Parasitology. In the same year, I. J. Thomason joined the UCR faculty. The academic staff of the new department increased rapidly in the next five to six years. D. R. Viglierchio joined the UCD faculty in 1955, and S. D. Van Gundy and R. Mankau joined the UCR faculty in 1957 and 1958 respectively. A. R. Maggenti joined the UCD faculty in 1959, while C. Castro was appointed at UCR in 1960. By the end of 1959, nematology at UCB had been closed by the transfer of M. W. Allen to UCD. W. H. Hart joined the UC Extension Service at UCD. By 1960, there were 13 professional nematologists in the University of California.
By 1962, the research competency of the staff broadened sufficiently for the University to approve of a name change to the Department of Nematology. In 1962, J. D. Radewald was appointed as a Cooperative Extension Specialist at UCR. In 1965, statewide University administration embarked on a decentralization program giving the individual campuses in the UC greater autonomy. As a result, the Statewide Department of Nematology was separated into individual departments at the UCR and at UCD. From 1965 onwards, the two departments evolved independently. In 1969, D. E. Johnson was appointed as a Cooperative Extension Specialist at the San Joaquin Valley Research and Extension Center at Parlier. At UCR, E. G. Platzer joined the Department in 1971. In 1972, R. C. Baines retired and was replaced by H. Ferris. M. V. McKenry was appointed in 1977, while S. A. Sher's death in 1975 led to the appointment of J. G. Baldwin in 1978. Upon the retirement of D. E. Johnson, a realignment of positions led to Cooperative Extension appointments of M. V. McKenry and P. A. Roberts in 1981 as faculty of UCR stationed at Parlier.
M. W. Allen (UCD) died in 1974, and in the same year, B. Lear was transferred to the Department of Plant Pathology. By July 1, 1976, the Department of Nematology, UCD, was reorganized by administrative action into a research unit (the Division of Nematology) with a chairman, but the teaching component was transferred to the Department of Entomology. In 1976, H. K. Kaya was appointed as an Assistant Professor at the UCD with a joint appointment in Entomology and Nematology.
Present & Future: 1985 to 2000
In 1984 Howard Ferris moved from UCR to assume the Chairmanship of the reinstated Department of Nematology at UCD. The UCD Department of Nematology has had the unique opportunity to completely restructure itself since 1985. Since that time, the nematology faculty at Davis has changed considerably; with the cumulative retirements of Hart, Lear, Lownsbery, Raski, Viglierchio, and Maggenti, and the additions of faculty members Jaffee, Westerdahl, Williamson, Caswell-Chen, and Nadler. The current faculty study nematodes in most habitats (except marine), and across a range of levels of biological organization, from the molecular to the community. Dr. H. Kaya is the current Chair of the Department.
The mission of the Department of Nematology at U.C. Davis is to be a center of excellence in all aspects of nematology by conducting research, educating and extending knowledge, and applying knowledge to solve problems.
- To develop new understanding, through research and scholarship, on the role, importance and management of nematodes in plant and animal health, and in environmental quality in terrestrial, freshwater, and marine ecosystems.
- To undergraduate and graduate students at UCD
- To the citizens of California
- To resource managers and advisors
- To researchers and educators worldwide
Applied Research & Extending Knowledge
- To conduct a vigorous applied research and extension program to benefit agriculture, environmental quality, and quality of life for citizens of California.
("What are Nematodes?" from Plant & Soil Nematodes, A report by the Committee on National Needs and Priorities in Nematology 1994, sponsored by the CSRS, USDA, and SON). ("Nematology in California" written by Maggenti and Caswell-Chen)