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

Abstract

Pathogenicity tests with Phytophthora cinnamomi were conducted on 25 perennial species from the jarrah (Eucalyptus marginata) forest of Western Australia. Most species tested had been found in a separate study to be scarce on sites affected by Phytophthora cinnamomi but frequently found in unaffected vegetation. Some species that were known to be field-tolerant of P. cinnamomi and some that were highly susceptible to infection were included in the study for comparison. Phytophthora cinnamomi was recorded from 13 of 17 species not previously known to be susceptible. Phytophthora cinnamomi was subsequently isolated from dead plants of two of these 13 species in the field. 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 field and glasshouse isolation of P. cinnamomi and the scarcity of this forb on dieback sites. It may also contribute to decline in populations of Boronia fastigiata, Hybanthus floribundus, Labichea punctata, Scaevola calliptera and Stylidium junceum, although further field sampling is required to confirm this.