Additions to the host range of Phytophthora cinnamomi in the jarrah (Eucalyptus marginata) forest of Western Australia

Pathogenicity tests with Phytophthora cinnamomi were conducted on 25 perenn ial species from the jarrah (Eucalyptus marginata) forest of Western Austra lia. Most species tested had been found in a separate study to be scarce on sites affected by Phytophthora cinnamomi but frequently found in unaffecte d vegetation. Some species that were known to be field-tolerant of P. cinna momi and some that were highly susceptible to infection were included in th e study for comparison. Phytophthora cinnamomi was recorded from 13 of 17 s pecies not previously known to be susceptible. Phytophthora cinnamomi was s ubsequently isolated from dead plants of two of these 13 species in the fie ld. The interpretation of results from the glasshouse trials was difficult for some species because of inconsistent patterns of death and P. cinnamomi isolation in the glasshouse trials. Phytophthora cinnamomi probably causes decline in wild populations of Stylidium amoenum, based on the ease of fie ld and glasshouse isolation of P. cinnamomi and the scarcity of this forb o n dieback sites. It may also contribute to decline in populations of Boroni a fastigiata, Hybanthus floribundus, Labichea punctata, Scaevola calliptera and Stylidium junceum, although further field sampling is required to conf irm this.