Phytophthora Root Rot: Assessing the potential threat to Australia's oldest national park


  • Jillian L. Walsh,

  • David A. Keith,

  • Keith L. McDougall,

  • Brett A. Summerell,

  • Robert J. Whelan

  • Jillian Walsh is a PhD student in the Faculty of Agriculture, Food and Natural Resources, University of Sydney (A05 McMillan Building, Sydney, NSW, 2006, Australia. Tel. 02 9531 3894. Fax 02 9531 6841. Email:; David Keith is a Principal Research Scientist with the NSW Department of Environment and Conservation (PO Box 1967, Hurstville, NSW 2220, Australia. Email:; Keith McDougall is a botanist with the NSW Department of Environment and Conservation (PO Box 2115, Queanbeyan, NSW 2620, Australia. Email:; Brett Summerell is the Director of Science and Public Programs at the Royal Botanic Gardens and Domain Trust (Mrs Macquaries Road, Sydney, NSW 2000, Australia. Email:; Robert Whelan is Dean of Science at the University of Wollongong (Northfields Ave, Wollongong, NSW 2522, Australia. Email: This study was initiated as an honours degree project in Environmental Science at the University of Wollongong by Jillian Walsh, and was later expanded for a broader examination of the distribution of Phytophthora cinnamomi in Royal National Park.


Summary  Royal National Park, Australia's oldest national park, is a significant reserve for conservation of the flora and fauna that are characteristic of the Hawkesbury Sandstone in New South Wales. Since at least 1974, Phytophthora Root Rot (caused by Phytophthora cinnamomi) has been known to occur in the Park, but there is no knowledge of the extent of infestation or the potential impacts of the disease within the Park. This study investigated the distribution of the pathogen within Royal National Park at two scales: a systematic survey by vegetation type, and a targeted survey of populations of Waratah and Spear Grass-tree. These two species are known to be susceptible to Phytophthora Root Rot and are therefore potential indicators of the impact of the pathogen on vegetation in Royal National Park. Phytophthora cinnamomi was recovered from all vegetation types sampled but most commonly in heathland/open scrub vegetation. The pathogen was easily recovered from sites containing Spear Grass-tree, but was not isolated from any sites containing Waratah. Because of the widespread distribution of P. cinnamomi, we conclude that hygiene measures will be of little use to prevent the spread of the pathogen within Royal National Park. Monitoring of the occurrence and spread of disease symptoms in plants and applying phosphite to protect susceptible rare or threatened flora may be the most appropriate management options.