Evaluating the Survival of Phytophthora ramorum in Firewood

John Shelly, University of California Cooperative Extension Advisor, Richmond Field Station, UC Richmond Field Station, Building 478, 1301 South 46th Street, Richmond, CA 94804, (510) 231-9414, john.shelly@nature.berkeley.edu; Ramnik Singh, Post Graduate Researcher, University of California, Richmond Field Station; Christine Langford, Staff Research Associate, University of California Richmond Field Station, Tad Mason, Forester, TSS Consultants, Rancho Cordova, CA

Many of the P. ramorum host species are a favored source for the commercial firewood industry. This study addresses the viability of P. ramorum in processed firewood and analyzes the unknown risk of spreading SOD by transporting and storing firewood products produced from SOD-diseased trees.

Preliminary data from an earlier study suggested that P. ramorum spores could survive on firewood for at least 6 months. Positive P. ramorum cultures were isolated on 8 of 49 freshly cut specimens and 1 of 30 specimens that had aged (air-dried) for 6 months. Following these initial results, a larger study was initiated. Approximately 7 tons of split firewood was selected from tanoak trees exhibiting the symptoms of SOD, and is being stored at a commercial firewood operation in Marin County with ambient temperature, humidity and rainfall data being monitored and recorded. A similar amount of firewood selected from the same diseased trees is being stored at the University of California - Richmond Field Station, on an outside concrete pad with simulated rain exposure reflecting periods of exceptionally high rainfall. Firewood specimens as well as water collected from the firewood pile runoff are periodically tested for presence of viable P. ramorum spores.

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