Dennis A. Johnson grew up in southeastern Idaho. He earned a B.S. degree in botany from Brigham Young University in 1973 and M.S. and Ph.D. degrees in plant pathology from the University of Minnesota in 1975 and 1978, respectively. He joined the faculty at Texas A&M University as an assistant professor of plant pathology in 1978, where he had research responsibilities for diseases of small grains at the Research and Extension Center in Vernon, TX. In 1980, he began working at the Washington State University (WSU) Irrigated Agriculture Research and Extension Station in Prosser as an assistant plant pathologist and extension plant pathologist to conduct a research and extension program in the epidemiology and management of diseases of a variety of irrigated field crops. He was promoted to associate professor in 1984 and full professor in 1990. He transferred to the main campus at WSU in Pullman, WA, in 1993, where he conducts a research and extension program and teaches a graduate class in plant epidemiology and disease management.
Johnson’s research and extension program has been highly successful in developing and integrating practical disease management strategies and tactics for a variety of crops. His recommendations are readily adopted by growers. He has made key contributions to understanding the epidemiology and management of several economic diseases, including late blight, black dot, white mold, and silver scurf of potato, and of Verticillium wilt of mint and potato. Important scientific contributions have been made in the areas of disease forecasting, quantitative characterization of spatial patterns of disease plants, characterization of partial resistance, and the etiology of Phytophthora infestans from latently infected potato seed tubers. In disease forecasting, he developed logistic regression models for the early and mid potato growing seasons that have been used successfully to manage late blight regionally in the Columbia Basin of Washington and Oregon for 15 years. Forecasting models also have been developed and implemented for growers in the Pacific Northwest for hop downy mildew and for improving timing of fungicide applications for potato white mold. The potato white mold model has saved the industry in Washington State more than $7.64 million annually since 2005. Potato growers in the western and midwestern United States also follow and benefit from his model through timely and judicious fungicide applications to control white mold. Using spatial analysis, Johnson documented yearly spread of Verticillium wilt in commercial mint fields, quantified the expansion and dispersion of late blight foci in commercial potato fields, and quantified the seasonal and yearly spread of hop downy mildew. Improved utilization and timing of management tactics have resulted from these spatial studies. Partial disease resistance has been characterized and selected by Johnson in barley and wheat to leaf rust, in asparagus to rust, in mint to rust and Verticillium wilt, and in potato to late blight. An understanding of the etiology of potato late blight was recently increased with two elegant studies that clearly demonstrated that Phytophthora infestans can survive latently in stored tubers, latently colonize newly emerged sprouts, and then sporulate during favorable conditions for continued infections.
During his career, Johnson has authored or co-authored 108 peer-reviewed research journal articles and well over 250 disease control bulletins and articles for growers. In recognition of his contributions to the industry, Johnson is an honorary life member of the Potato Association of America and recipient of the Friend of the Mint Industry Award, presented by the Washington Mint Commission.
Johnson is most proud of his role in mentoring graduate students. Fifteen advanced degrees have been awarded to students he advised. They are now productive in science careers. He is currently advising two Ph.D. students. He teaches the graduate course “Plant Epidemiology and Disease Management” at WSU. The class historically has full enrollment and draws graduate students from plant pathology and related disciples. He teaches with enthusiasm, and students appreciate the exposure they receive to practical and theoretical plant epidemiology.
Johnson has given 28 invited presentations to growers outside of Washington since 2000. He was an invited speaker at the first Potato Expo in San Antonio, TX, in 2009. He gave an invited presentation, “Verticillium wilt of potato: The pathogen, disease, and management” at the Canadian Phytopathological Society’s Annual Meeting in Winnipeg in 2009. In 1989, he was invited by Volunteers in Overseas Cooperative Assistance to address a crop-limiting disease of asparagus in Java, Indonesia. He subsequently described an unreported foliar blight of asparagus, described the pathogen Phomopsis javanica, and established a disease management plan for the region.
Johnson is highly regarded as an authority on diseases of potato. Recently, he edited the second edition of the APS publication, Potato Health Management, and raised significant contributions to cover publication costs of the book. The book is widely used in the potato industry. In addition, he has authored several sections in the APS Disease Compendia on potato, hop, and onion.
Johnson has been active in service to professional societies, especially APS. In addition to his APS publications, he has served on the Extension Committee (1988–1991), Integrated Pest Management Committee (1985–1988), and Plant Disease Losses Committee (1982–1985). He also has been active in the APS Pacific Division, serving on the Planning and Local Arrangement Committee (1984), Nominating Committee (1992), and as president (2008–2009). In 2010, he served on the Planning Committee for the joint APS Pacific Division and Canadian Phytopathological Society meeting in Vancouver, BC. He also was on the Planning and Local Arrangement Committee for the Potato Association of America Annual Meeting in Spokane in 2003.
Johnson’s sustained record of working in a unique and demanding crop production system, his research productivity, mentorship of graduate students, and his successful extension of his researching findings into effective disease management programs for growers make him most deserving of the APS Fellow Award.
