Early detection monitoring of Phytophthora ramorum in high-risk forests of California

Early detection monitoring is essential for successful control of invasive organisms. Detection of invasions at an early stage of establishment when a population is small and isolated makes eradication more feasible and less costly. Sudden oak death, caused by the recently described pathogen Phytophthora ramorum, is an emerging forest disease that has reached epidemic levels in coastal forests of central and northern California. To control the spread of the pathogen and protect susceptible habitats, California has established an extensive monitoring program focused on early detection of pathogen activity at isolated locations, where it may be possible to apply chemical treatments or attempt eradication. It is also essential to understand when and where the risk of establishment is elevated in order to effectively monitor the pathogen and manage threatened forests in a state as large (408,512 km2) and environmentally variable as California. Funded by the USDA Forest Service and California Department of Forestry and Fire Protection, the objectives of this research are to: (1) use GIS-based risk modeling to target early detection sampling efforts in the most threatened forests across the state of California; and (2) discover emergent infections of P. ramorum before they become well-established. Here, we present two years (2003-04) of results from California’s early detection survey of P. ramorum.