Second Science Symposium
January 18 - 21, 2005
Monitoring Phytophthora ramorum Distribution in Streams within Coastal California Watersheds
Shannon K. Murphy, John Bienapfl, and David M. Rizzo, Department
of Plant Pathology, University of California, Davis, CA 95616; (530) 754-9894;
Thirty-five locations were established in winter-spring 2004 to monitor for the presence of Phytophthora ramorum (Pr) in perennial watercourses throughout coastal northern California. The areas of focus included Alameda, Contra Costa, Del Norte, Humboldt, and Mendocino counties. These counties have limited Pr detection but are high-risk areas for Pr infestation. Two sites in Sonoma County were included as a baseline for successful recovery of Pr.
Rhododendron leaves were placed in mesh bags and secured in watercourses for 1 to 3 week intervals year-round to bait for Phytophthora species. Recovered symptomatic leaves were plated on Phytophthora-selective media.
Pr was recovered at all sites with a priori knowledge of Pr forest infestation. We recovered Pr at three sites downstream of known forest infestations. One site is along the South Fork Eel River, approximately 8km downstream of known infestation near Redway. Additionally, Pr was recovered at two sites without prior known forest infestation in Briones Regional Park.
Stream monitoring provides a useful method of early detection
for Pr infestation. Future work will include the additional monitoring
at the southern extent of the known Pr range. In addition, we will address
research questions related to spread and survival of this pathogen in
| Coordinated by:
USDA Forest Service Pacific Southwest Research Station
University of California Integrated Hardwood Range Management Program,
Center for Forestry, Division of Agriculture and Natural Resources, and
California Oak Mortality Task Force
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