Surveying For and Eradicating Phytophthora ramorum in Agricultural Commodities

Since 2001, Oregon nurseries, Christmas tree plantations, and other sites have been surveyed for the federally regulated pathogen Phytophthora ramorum. Host plants at each site were visually surveyed for disease symptoms and symptomatic tissues tested in the laboratory by isolation onto a selective medium and by a polymerase chain reaction (PCR) assay. In 2002 and 2003, we detected PCR-positive plants that later proved to be infected with another Phytophthora, suggesting there are limitations to the PCR assay tested. In 2003, P. ramorum was detected for the first time in Viburnum, Pieris, Rhododendron, and Camellia plants in six nurseries. All infected and neighboring plant materials were destroyed by incineration and the nurseries and surrounding environs subsequently surveyed for the pathogen. Phytophthora ramorum was not detected, indicating the pathogen was successfully eradicated.