Abstract
The Eucalyptus rudis (flooded gum) is in decline across its range in the south-west of Western Australia. It is a keystone species in riparian ecosystems where it provides important ecosystem functions such as habitat provision and water quality maintenance. Symptoms of decline resemble dieback symptoms caused by pathogens from the genus Phytophthora. The rhizosphere soil of E. rudis, and water, were sampled along several watercourses in the south-west and species of Phytophthora isolated. Several species were recovered from soils and water, including P. multivora and P. elongata, two species which are believed to be involved in Eucalypt decline. None of the species recovered acted as primary pathogens on E. rudis in pathogenicity tests, but they may be acting in conjunction with other biotic and abiotic factors in the field. Several different treatments, including phosphite, insecticide and complete (macro- and micro-) nutrients, were tested on mature E. rudis in a Perth wetland to compare their effectiveness in restoring health. The health of these E. rudis were also assessed using aerial remote sensing imagery. The results of this study will have significant implications for the diagnosis and treatment of Eucalyptus rudis decline.