It has been two decades since the first detection of the sudden oak death pathogen Phytophthora ramorum in Oregon forests. Although the epidemic was managed since its first discovery in 2001, at least three invasions of three separate variants (clonal lineages), NA1, EU1, and NA2, are documented to have occurred to date. Control of this epidemic has cost over US$32 million from 2001 to 2020. This is dwarfed by the predicted cost of the closure to the Coos Bay export terminal, estimated at $58 million per year, if the epidemic was allowed to spread unchecked. Management efforts in Oregon have reduced inoculum and limited the spread of the pathogen. An outreach and citizen scientist program has been piloted to help in early detection efforts and search for disease-resistant tanoak. This feature article documents the repeated emergence, impact, costs, and lessons learned from managing this devastating invasive pathogen.
Keywords: disease management; epidemiology; forest trees; oomycetes; pathogen diversity.