Phytophthora species associated with disease in peri‐urban woodland and forest ecosystems

Perth, the capital city of Western Australia, is situated on a river with numerous bays. The peri‐urban environment extends along the coast for 100 km north and south of the city. Within the region is a fragmented landscape of suburbs, parks and remnant woodlands. The Eucalyptus gomphocephala woodland south of Perth is classified within the peri‐urban environment. Numerous Phytophthora species have been isolated from dead and dying endemic trees. The most frequently isolated species is P. multivora (65%), followed by P. aff. arenaria (21%); P. palmivora, P. syringae, P. inundata, P. aff. humicola, P. nicotianae and P. sp. ohioensis have also been isolated, although rarely. P. multivora and P. aff. arenaria have both been isolated from dying E. marginata (jarrah), E. gomphocephala (tuart), Corymbia calophylla (marri), C. ficifolia (red flowering gum) and Agonis flexuosa (WA peppermint). While P. multivora is commonly encountered in less impacted ecosystems, the other species found in the periurban environment (P. inundata and P. nicotianae) are rarely or never isolated. In the riparian ecosystem, P. aff. humicola has been isolated from dying Casuarina obesa. The knowledge about the impact of these species on our remnant trees is lacking. Further research is required on the origin, pathogenicity and control of these species to deliver effective management strategies