Host and Habitat Index for <em>Phytophthora</em> Species in Oregon

Abstract

Phytophthora species are abundant in streams in healthy forests and widespread in forest soils causing cryptic diseases, in addition to their more traditional roles as aggressive pathogens. We compiled existing Oregon records from available sources of reliably identified Phytophthora species from forests and forest trees and summarized the results by host and habitat in an interactive online database. Details of documented isolates including locations, available cultures, Genbank acquisition numbers, and citations are in an accompanying supplemental spreadsheet. Thirty-two Phytophthora species have been identified associated with 25 host species from Oregon forests or forest trees. This total includes 19 species recovered from forest streams and 19 from forest soils, generally in the absence of noticeable disease on associated vegetation.

A total of 29 Phytophthora species were identified from the various environments in forests. Fourteen species came from trees or forest shrubs growing in cultivated and urban environments. Only three species were unique to the latter, however, including P. ilicis, from cultivated holly (Ilex), and P. sansomeana and P. taxon ceanothus from forest nurseries. Three species, P. gonapodyides, P. taxon oaksoil, and P. taxon salixsoil were recovered from streams in all surveyed counties. The most widespread species causing root disease or bole cankers of trees was P. lateralis on Port-Orford-cedar in landscape plantings throughout the state as well as on forest trees in its limited native range. P. cambivora and P. cinnamomi were widespread but uncommon on a number of forest trees.