Distribution of Phytophthora ramorum, P. nemorosa, and P.pseudosyringae in native coastal California forest communities

Abstract

Phytophthora ramorum, causal agent of sudden oak death, is well established over approximately 450 km of native forest along the California coast. In the course of research on this invasive exotic pathogen, two other putatively exotic aerial Phytophthora species, P. nemorosa and P. pseudosyringae, were discovered (Ivors and others 2004, Linzer and others 2006). Little is known about the ecology and biology of these other species and how they interact with P. ramorum. Preliminary research has found that P. nemorosa and P. pseudosyringae have similar host and geographic ranges and cause similar disease symptoms as P. ramorum (Hansen and others 2003, Murphy and Rizzo 2006, Wickland and Rizzo 2006). However, P. nemorosa and P. pseudosyringae do not appear to cause landscape level mortality of oaks (Quercus spp.) or tanoak (Lithocarpus densiflorus) and infect fewer plant species, as does P. ramorum. Additionally, while all three pathogens are patchy over the landscape, P. nemorosa and P. pseudosyringae are distributed over a broader geographical area than P. ramorum, extending into the Sierra Nevada. Symptoms caused by these three species are indistinguishable in the field and the causal species can only be identified using either molecular methods or microscopically once cultured.

Parent Publication

• Proceedings of the sudden oak death third science symposium

Citation

Murphy, S.K.; Wickland, A.C.; Lynch, S.C.; Jensen, C.E.; Maloney, P.E.; Rizzo, D.M. 2008. Distribution of Phytophthora ramorum, P. nemorosa, and P.pseudosyringae in native coastal California forest communities. 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. 51-54