Research on the Quarantine Pathogen Phytophthora ramorum at the National Ornamentals Research Site at Dominican University of California (NORS-DUC)

Phytophthora ramorum, the causal agent of Sudden Oak Death and Ramorum blight, can infest several dozen host plants, among them many important ornamental plants like Rhododendron, Viburnum and Camellia. Federal and state regulations require the destruction of nursery plants infected by P. ramorum and treatment of contaminated soil. Infected nursery material is also a possible factor in the long-range spread of P. ramorum. The National Ornamentals Research Site at Dominican University of California (NORS-DUC) was founded in the year 2009 by a Farm Bill grant to study P. ramorum in a sophisticated research nursery that reflects an authentic commercial nursery setting (www.dominican.edu/norsduc). NORS-DUC goals are to develop practical solutions for containment, remediation, and eradication of quarantine pathogens in nurseries, reducing the risk of long-range spread of pests through infested nursery stock shipments. Research at NORS-DUC is conducted by a team of permanent staff as well as by P. ramorum experts from other institutions who can apply for grants to work at NORS-DUC. The research site offers a unique opportunity to study different aspects of P. ramorum diseases of ornamentals that has not been accomplished previously. First results from research on the eradication of P. ramorum from soils using steam sterilization, solarization and bio-control using a new Trichoderma isolate indicate they were effective; and these methods are being reviewed by USDA APHIS as approved for soil treatments in infected commercial nurseries. Ongoing research is focusing on the disease epidemiology in nurseries, the genetic plasticity of P. ramorum on different host plants and the effects of fungicides and physiological stress on symptom development.