2006 pilot survey for Phytophthora ramorum in forest streams in the USA

Abstract

Methods for detecting Phytophthora ramorum and other Phytophthora species with rhododendron leaf baits were pilot tested in high-risk watersheds in 11 states for the purpose of recommending a national survey protocol. Ninety streams, including 14 draining P. ramorum.-endemic areas, yielded 587 baiting chances. Molecular diagnostic assays detected the pathogen in all known P. ramorum-endemic streams at least once in five baiting periods, and in nearly 50 percent of all bait leaf sets. Isolation using selective media detected the pathogen in all but one known positive stream in California and Oregon, and for the first time in one Washington stream draining a confirmed positive ornamental nursery. Overall, Phytophthora spp. were detected by isolation in all but one stream over the course of the pilot survey, and in over 80 percent of the leaf bait sets. The national P. ramorum early detection survey for U.S. forests will recommend rhododendron leaf baiting for five baiting periods in high-risk watersheds with redundant molecular and selective media isolation assays for 2007.

Parent Publication

• Proceedings of the sudden oak death third science symposium

Citation

Oak, S.W.; Hwang, J.; Jeffers, S.N.; Tkacz, B.M. 2008. 2006 pilot survey for Phytophthora ramorum in forest streams in the USA. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 59-64