Second Science Symposium
January 18 - 21, 2005

Predicting the Potential for Establishment of Phytophthora ramorum in the Oak Forests of the North Central States in the USA

Susan D. Cohen, USDA APHIS PPD, 4700 River Road Unit #117, Riverdale, Maryland 20737; (301) 734-5929;; Robert C. Venette, University of Minnesota, Department of Entomology, 1980 Folwell Ave., St. Paul, Minnesota 55108; (612) 625-1956;

The movement of nursery stock provides a means of transporting Phytophthora ramorum into new locations of the USA, including the North Central region. Susceptible hosts and favorable climate conditions are required for subsequent establishment of the pathogen. Since susceptible hosts grow in this region, this study focuses on predicting the area of establishment of P. ramorum based on climate conditions. Two methods using the climate-analysis software CLIMEX are used to measure the suitability of temperature and moisture for establishment of P. ramorum in the North Central states. The first method compares the similarity of climates in areas with and without disease. Disease presence/absence was determined from records provided by Maggi Kelly (UC Berkeley) and NAPIS database ( The percentage of maximum similarity results are then displayed using a mapping program (ARC-View, ver. 8.3). The second method generates an index based on modeling fungal physiological growth and survival responses (from published literature) to climate variables that occur in different geographic areas. Because these predications are based on different data sources, their complimentary information identifies areas most at risk for P. ramorum establishment. Where the predictions from the two models give conflicting results, there is a high level of uncertainty.

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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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