Relationships between site factors and distribution of Phytophthora cinnamomi in the Eastern Otway Ranges, Victoria

The Eastern Otway Ranges, Victoria is an area recognised for its significant flora and fauna communities. An area of about 7000 ha, the Anglesea heathlands has been listed on the register of the National Estate. Although symptoms of the plant pathogen Phytophthora cinnamomi have been recorded in the area since the 1970s, the extent of infestation and its effects have not been documented. The aims of this study were to assess the distribution of infestation, identify the relationship of plant infection to site variables and to identify evidence of spread of the pathogen. The presence of P. cinnamomi was assessed at 50 study sites by a visual evaluation of the vegetation, using species such as Xanthorrhoea australis (Austral grass tree) and Isopogon ceratophyllus (horny cone bush) as indicator species. Soil and plant tissues were assayed for the presence of the pathogen by cotyledon baiting and immunoassay methods. Phytophthora cinnamomi was isolated at 76% of the study sites from the floristic communities identified: heathy open forest; heathy woodland I and II; Bald Hills heathland; riparian open forest. There were significantly more diseased sites at lower altitudes. The pathogen is widely spread and causing disease throughout the area, but at present often only in small patches. There is an urgent need for disease management to protect the significant communities. These findings suggest that management actions such as mapping current infestations, closing tracks and implementing vehicle wash-down points are required.