Rate My Professor Scott Harper

Scott Harper is an Associate Professor of Virology in the Department of Plant Pathology at Washington State University. He earned his BSc in 2003, MSc (Hons) in 2005, and PhD in 2009 from the School of Biological Sciences at the University of Auckland, New Zealand. Following his PhD, Harper worked as a Scientist Level 1 at the Plant Health and Environment Laboratory, Ministry of Agriculture and Forestry, New Zealand, from 2008 to 2010. He then conducted postdoctoral research at the Citrus Research and Education Center, University of Florida, from 2010 to 2015, and served as Research Assistant Scientist in the University of Florida Department of Plant Pathology from 2015 to 2016. In 2017, he joined Washington State University as Assistant Professor and Director of the Clean Plant Center Northwest (CPCNW), where he was granted tenure and promoted to Associate Professor effective July 1, 2023.

Harper's research focuses on viruses and other systemic pathogens affecting perennial crops in the Pacific Northwest, particularly fruit trees (Malus and Prunus spp.), grapevines (Vitis sp.), and hops (Humulus lupulus). His studies investigate virus-virus interactions and their effects on virus movement, transmission, and disease expression; viral infection processes, tissue tropism, detection, and eradication; and the development of new diagnostic assays and tools. As Director of CPCNW since 2017, Harper has led the propagation, maintenance, and distribution of virus-tested planting materials for fruit trees, grapevines, and hops, preventing disease introductions and supporting international trade. His contributions include key research on little cherry disease/X disease, identifying its causal agent and exploring methods to disrupt its progression. In 2025, he received the Excellence in Regulatory Affairs & Crop Security Award from the American Phytopathological Society for advancing regulatory plant pathology and crop security. Select publications include "Sequence variation in two genes determines the efficacy of transmission of Citrus tristeza virus by the brown citrus aphid" (Archives of Virology, 2016), "Minor coat and heat-shock proteins are involved in binding of Citrus tristeza virus to the foregut of its aphid vector" (Applied and Environmental Microbiology, 2016), "Finding balance: virus populations reach equilibrium during the infection process" (Virology, 2015), and "Recovery Plan for X-Disease in Stone Fruit Caused by 'Candidatus Phytoplasma xdisease'" (2023). Harper's work bolsters Washington's agriculture, which produces nearly 75 percent of U.S. hops.