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Ivan James Thomason

Professor of Nematology and Plant Pathology, Emeritus

UC Riverside

1925 – 2008


Ivan James Thomason died on January 26, 2008 at age 82. Soon after his birth in Burney, California, the family moved to Davis, CA, where Ivan grew up and attended school. After graduation from high school with honors, he put his dream to attend college on hold and volunteered in the US Army Corps of Engineers during World War II (1943-1946). He served in the South Pacific beginning in 1944 and was in Okinawa, Japan, when the War ended in 1945. Upon Ivan’s return from the army, he attended the University of California (UC) Davis where he earned his B.S. degree in plant sciences. He was attracted to the field of plant pathology after taking a required course in this subject. As an undergraduate he worked with renowned plant pathologists Drs. Lysle Leach and Jack Oswald. In response to their encouragement to pursue higher education, in 1950, he joined the University of Wisconsin, Madison where he received M.S. and Ph.D. in plant pathology under the direction of Dr. James Dickson, Cereal Pathologist. In 1954, soon after graduation, he joined the Department of Plant Pathology at the Citrus Experimental Station at Riverside, California. At the time, Ivan had little knowledge about nematodes and nematode diseases. In 1956 Ivan was appointed as an Assistant Nematologist in the Department of Plant Pathology and the Department of Nematology. He was At UC Riverside, Ivan built a nationally and internationally recognized program in Nematology.


Ivan Thomason’s research addressed the biology and control of root-knot and cyst nematodes. Early in his career, he experimented with chemical control but he was more interested in population dynamics of Heterodera schachtii on sugarbeets and developed a rotation program for sugarbeets that continues to be used by the industry in the Imperial Valley, California. Later in his career, Ivan’s research focused on breeding resistant crop varieties. His research identified heat stable root-knot nematode resistance sources in wild relatives of tomato. Just before his retirement, his group had identified root-knot nematode resistance sources in blackeye beans, lima beans and carrots, and this work laid the foundation for new ongoing investigations.


Ivan was known and respected for his leadership qualities and service. He served as the chair of the Department of Nematology at UC Riverside from 1962 to 1969. His easygoing manner and infectious laughter served him well in bringing together colleagues to work on multidisciplinary problems. He served as the California (statewide) pest management program director from 1976-1982, was the cofounder of the statewide UC Integrated Pest Management Program, and provided leadership as the IPM director from 1980-1983. Service on additional statewide committees included the Pesticide Advisory Board, and Science and Technology Review Committee. He was vice-chairman of the UC systemwide Academic Senate Faculty Welfare Committee and numerous other UC Committees. Ivan retired from University of California in 1989. Even in retirement, Ivan continued to serve UC as president of UC Riverside Emeriti Association. In 1999, the UC Riverside Emeriti Association bestowed on Ivan the Outstanding Emeritus Faculty Award.


Ivan was a strong mentor for new UC Riverside faculty, postdoctoral fellows and graduate students from around the world. He encouraged and nurtured creativity and influenced many young Nematologists. Ivan and his wife Harriet, generously established the UCR Ivan and Harriet Thomason Research Endowment in support of graduate students in nematology.


Ivan was an active member of Society of Nematologists (SON) and the American Phytopathological Society (APS) and various nematology organizations. He served as vice president and president of SON from 1974 to 1976. He was honored by both SON and APS for his distinguished contributions to the science of Nematology and Plant Pathology with his election as Fellow of SON in 1983 and Fellow of APS in 1988.


Ivan cared about his community and gave his time and energy in several ways. He was a member of the Kiwanis club in Riverside and was involved in tutoring children in math and science. He especially enjoyed teaching at the School Farm, extending to young urban children knowledge of how plants and vegetables were planted and how they grew and produced food. He also volunteered in his church kitchen to feed the homeless. He was a dedicated husband to his wife Harriet, who preceded him in death, and his family tells of many incidents extolling his role as a great father and grandfather.


Ivan was an avid bird watcher. After retirement, he took several international trips to visit his former students and always managed to work in a bird watching trip on these travels. He also spent time on his duck carving hobby and other woodworking projects. Ivan had a friendly personality and was an excellent storyteller. He quickly made friends, enjoyed the company of others, and had many cherished lifelong friendships. Several of Ivan’s colleagues from University of Wisconsin ended up at UC Riverside. Ivan’s friendships with these colleagues continued to the end. They met almost daily at a coffee and doughnut shop near the University where they exchanged heated but friendly debates. Ivan’s legacy is one of an extraordinary work ethic and high standards in research and service. His colleagues at Riverside most remember him as one that encouraged and challenged in a way that brought out the best in all of us.


Isgouhi Kaloshian

Seymour D. Van Gundy

James G. Baldwin