Port Orford cedar infected by Phytophthora lateralis in the Pacific Northwest, USA

Port-Orford-cedar (Chamaecyparis lawsoniana [A. Murr.] Parl.) is an ecologically and economically important tree species. Its natural range is geographically limited to southwestern Oregon and northwestern California, but within that area, it occupies a broad environmental range. Port-Orford-cedar can be an important component of the riparian community, providing stability and shading. It can be found on ultramafic soils as well as non-ultramafic soils.

Port-Orford-cedar is affected by an exotic root pathogen, Phytophthora lateralis (Tucker and Milbrath), which was first documented in a nursery near Seattle, Washington, in 1923. The pathogen is believed to have spread south via infected nursery stock and infested soil, and was first reported in the natural range of Port-Orford-cedar in 1952 near Coos Bay, Oregon. By 1960, infected trees were found on the Siskiyou National Forest, and surveys in 1964, 1974, 1983 and 1986 showed increasing levels of infestation and tree mortality. Infected trees were first identified in California in 1980. The pathogen now infects Port-Orford-cedar on about nine percent of the acreage of federally-administered lands within the range of the species. Most of this acreage is on sites of high risk to spread the pathogen, i.e., along streams and roads.

This dataset represents the Port Orford cedar extent in Northern California and Southern Oregon. Areas not infected by P. lateralis are shown in green, while those affected are shown in red.