Understanding the Disposal and Utilization Options for Phytophthora ramorum

Removing trees inflicted with the sudden oak death (SOD) disease is often necessary because of hazard issues or homeowner/landowner desires. An alternative to disposal of this material is to find acceptable uses for this diseased material. A series of studies is being conducted to help understand the risk of spreading the Phytophthora ramorum infested wood through disposal and utilization activities. Two collection yards were set up in California for wood suspected of being infected with P. ramorum, one in Marin County and one in Santa Cruz County. More than 1,155 tons of woody, P. ramorum host material has been processed through the collection yards since May 2003, most from the removal of hazard trees. This material was converted into fuel for biomass power plants, firewood, and lumber. In addition to operating the collection yards, this project included periodic monitoring for P. ramorum spores during various stages of the processing and transportation by sampling the delivered host material and monitoring the host vegetation growing in and around the collection yards. The periodic sampling of woody materials transported to and processed in the collection yards yielded a small number of positive cultures of P. ramorum isolated from a variety of the unprocessed and processed materials. Of the 418 samples collected, the following tested positive: two of 84 chip samples, two of eight California bay laurel leaf samples, eight of 145 samples of freshly split firewood, one of 85 samples of firewood air dried for about 6 months, nine of 93 grinder and saw dust samples, and one of three rainwater runoff samples. Furthermore, the sampling results of the host vegetation growing in and around the collection A version of this paper was presented at the Sudden Oak Death Second Science Symposium: The State of Our Knowledge, January 18-21, 2005, Monterey, California. This project is in part co-funded by the USDA Forest Service, Region 5 State and Private Forestry and the California Department of Forestry and Fire Protection (CDF), under CDF Agreement # 8-CA-01257. 2 University of California Cooperative Extension Advisor, [email protected]; Post Graduate Researcher, [email protected]; Staff Research Associate, [email protected]; University of California Richmond Field Station, Richmond, CA 94804. 3 Forester, [email protected]; TSS Consultants, Rancho Cordova, CA GENERAL TECHNICAL REPORT PSW-GTR-196 468 yards confirmed the presence of P. ramorum at each site before operations began but continued sampling has not revealed any significant infestation increase. This early data suggests that alternatives to disposal exist for P. ramorum-infested wood. Furthermore, although P. ramorum can be isolated from various stages of processing at the collection yards, no evidence has been gathered to support the hypothesis that the collection, sorting, and processing activities in the collection yards increases levels of P. ramorum infestation in and around the sites.