The distribution of Phytophthora in the Greater Blue Mountains WHA.
Disease caused by Phytophthora cinnamomi is becoming increasingly prevalent within the Greater Blue Mountains World Heritage Area (GBMWHA), yet little is known of the distribution of pathogens or the impact of disease. An understanding of the disease distribution is required to develop management strategies in natural ecosystems like the GBMWHA. However where only sporadic information is available, conservation efforts may be limited by incomplete sampling for pathogen presences due to remoteness and inaccessibility of many sites. Risk models can overcome some of these drawbacks. Hence, we modelled the distribution of P. cinnamomi in the GBMWHA by combining landscape and environmental information using a GIS approach. Data layers were reclassified into risk layers using FUZZY logic such that localities conducive to dieback were given the highest risk rating enabling the compilations of a relative risk surface. The area identified with the highest risk was the Blue Mountains National Park primarily due to optimal temperatures for pathogen development, known infestations and an abundance of roads, tracks and paths To investigate the range of Phytophthora infestation soil sampling was conducted based on the risk levels in the model using a stratified random approach. Results indicate the pathogen is widespread across the WHA. However, infestation is sporadic with negative samples occurring frequently. Isolations were more common in areas of greater human activity, such as the highly visited Blue Mountains National Park. Results also implicate vehicles in anthropogenic dispersal. Further testing is being undertaken to improve our understanding of the pathogen-environment-disturbance relationship and genetic analysis of isolates will explore inter and intraspecific species variation. Information gained from the survey will allow managers to prioritise hygiene and quarantine measures, and facilitate the development of ecological models of the distribution of Phytophthora within the GBMWHA.