Botanic Gardens Trust, Sydney, Australia

2. Research & Education Projects: Botanic Gardens Trust

Phytophthora Dieback in National Parks in New South Wales

Brett Summerell & Edward Liew, Plant Pathologists
Jillian Walsh
Chris Howard, PhD student
Rose Daniel & Therese Suddaby, Project Officers

The Royal Botanic Gardens & Domain Trust has been working through a number of projects on Phytophthora Dieback in National Parks in New South Wales for a number of years. Phytophthora Dieback is an exotic introduced disease of a wide range of native plants that has been recently discovered to be affecting plants in a number of national parks in New South Wales.

A collaborative research project between scientists at Sydney's Botanic Gardens and the NSW National Parks and Wildlife Service has discovered the presence of disease in national parks such as Royal National Park, Barrington Tops National Park and Werrikimbee National Park. This disease has been listed as a Key Threatening Process to native vegetation in New South Wales.

Not all plants are susceptible to the disease but those that are often rapidly killed by the pathogen. Grass trees (Xanthorrheoa spp.) are particularly susceptible and usually rapidly die. Many rare and threatened plants, such as the Wollemi Pine, are susceptible to the disease and special precautions must be taken to prevent the pathogen from entering the areas where these trees grow.

Jillian Walsh

A study by Jillian Walsh 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. As both species are known to be susceptible to Phytophthora Dieback they are potential indicators of the impact of the pathogen on vegetation in Royal National Park (Walsh et al. 2006).

Chris Howard

The findings from the study by Christopher Howard for his PhD thesis (Howard 2008), of genetic variation of Phytophthora cinnamomi in NSW, have implications on the management of Phytophthora Dieback in natural ecosystems of NSW. His survey of National Parks in NSW looked at genetic variation in P. cinnamomi to better understand if P. cinnamomi was native to NSW. It was once thought to be native to NSW or introduced such a long time ago that indigenous plants had developed resistance to it but this study shows that this is not the case. Interestingly the study found there is a considerable imbalance of mating type abundance and that genetic variation is no greater than found elsewhere in Australia, where it is regarded as an introduced species. The study did reveal a greater amount of genotypic diversity in diseased areas in close proximity to urban areas, indicating that human activity is linked to the presence of higher genetic variation in P. cinnamomi. Additionally, higher levels of human activity are linked to greater risk to an ecosystem. The study also revealed that different genotypes found in NSW vary in their pathogenicity on multiple hosts. Therefore it should not be assumed that the dynamics of an infestation are static. Reinfestation by a new genotype could devastate what appears to be a tolerant species. The simple land management lessons from this study are that:

  • P. cinnamomi is a recently introduced pathogen to NSW
  • P. cinnamomi is associated with European settlement, so it cannot be assumed that any resistance to Phytophthora Dieback disease has been developed through long association with the pathogen
  • As P. cinnamomi is associated with human activity all ecosystems where humans visit are at risk of Phytophthora Dieback
  • Different genotypes of P. cinnamomi differ in their ability to infect different plant species and cause disease. So species may be relatively resistant to one genotype but highly susceptible to another
  • As increased levels of human activity are linked to greater genetic variation of P. cinnamomi in an area, any increased activity is also linked to greater risk of the number of plant species being infected by Phytophthora Dieback
  • In an ecosystem, where a soil test reveals the presence of P. cinnamomi, and which appears to be resistant to Phytophthora Dieback may be devastated by the introduction of a different genotype of P. cinnamomi.

Protection by good hygiene practices is the first level of defence. There is no way of visually determining if P. cinnamomi is in the soil and rarely is genotype analysis done when testing for the presence of P. cinnamomi.

Rose Daniel & Therese Suddaby - CMA studies

Studies of the Sydney Metropolitan and Hawkesbury-Nepean Catchment Management Authorities (CMA) in 2008 resulted in the production of the brochure Facts about Phytophthora, maps of the distribution of Phytophthora cinnamomi in these CMA areas, the production of best practice management plans as well as a report of the susceptibility of selected NSW plant species to P. cinnamomi (see references below). 

The Best Practice Management Guidelines provide details on developing a survey plan, taking samples, hygiene protocols and treating infected areas. Although these Guidelines were developed for the Sydney Metro CMA the practices can be adopted for the management of Phytophthora Dieback in other areas of NSW.

There are many ways in which this disease can be spread including spread on vehicles and bushwalkers and by feral animals such as pigs. There are also concerns that residents living on the edge of national parks could introduce the disease by planting infected plants in their gardens.

Continuing research

On-going research programs aim to survey and map where the pathogen is present and to determine its impact on rare and threatened species in New South Wales. We are using molecular tools to fingerprint the pathogen in different regions so that we can determine their relationships to each other and understand how the pathogen has been spread between and within our national parks.

References

  • 2008. Howard CG. A contemporary study of the genetic variation of Phytophthora cinnamomi recovered from natural ecosystems of New South Wales. PhD Thesis, University of Sydney.
  • 2003. McDougall KL & Summerell BA. The impact of Phytophthora cinnamomi on the flora and vegetation of New South Wales - a re-appraisal. In Phytophthora in Forests and Natural Ecosystems. 2nd International IUFRO Working Party 7.02.09 Meeting, Albany, Western Australia, October 2001. Eds. JA McComb, GE St J Hardy and IC Tommerup; pages 49-56. (Murdoch University Print: Murdoch, Western Australia).
  • 2003 McDougall KL, Summerell BA, Coburn D and Newton M. Phytophthora cinnamomi causing disease in subalpine vegetation in New South Wales. Australasian Plant Pathology 32: 113-115.
  • 2005. Summerell B, Pongpisutta R & Howard C. The biology of Phytophthora cinnamomi, Australasian Plant Conservation 13(4). More.
  • 2006. Walsh J, Keith D, McDougall K, Summerell B & Whelan R. Phytophthora Root Rot: assessing the potential treat to Australia's oldest national park, Ecological Management & Restoration 7(1): 55-60. More.
  • 2003. Walsh J, McDougall KL, Whelan R and Summerell BA. The distribution and impact of Phytophthora cinnamomi in Royal National Park, New South Wales. In Phytophthora in Forests and Natural Ecosystems. 2nd International IUFRO Working Party 7.02.09 Meeting, Albany, Western Australia, October 2001. Eds. JA McComb, GEStJ Hardy and IC Tommerup; pages 280-281. (Murdoch University Print: Murdoch, Western Australia).

See documents from the Sydney Metropolitan Catchment Management Authority Area project.

  • 2008. Suddaby T & Liew E. Best Practice Management Guidelines for Phytophthora cinnamomi in the Sydney Metropolitan CMA (982 Kb PDF file).
  • 2008 Suddaby T. Survey locations within the Sydney Metropolitan CMA (Map - 1.2 MB PDF file).
  • 2008 Suddaby T. Survey of the distribution of Phytophthora cinnamomi  in bushland of the Sydney Metropolitan Catchment Management Authority (620 KB).
  • 2008 Suddaby T. The susceptibility of selected NSW plant species to Phytophthora cinnamomi  (517 KB PDF file).

See documents from the Hawkesbury Nepean Catchment Management Authority Area project.

  • 2008 Suddaby T & Liew E. Best Practice Management Guidelines for Phytophthora cinnamomi within the Sydney Metropolitan Catchment Management Authority Area. (33 pp. - 516 Kb MSWord document).
  • 2008 Suddaby T & Liew E. Phytophthora cinnamomi in the Hawkesbury Nepean Catchment Management Authority Area (Map - 1 Mb pdf).
  • 2008 Suddaby T. Susceptibility of selected NSW plant species to Phytophthora cinnamomi (11 pp. - 398 KB MSWord document)
  • 2008 Suddaby T. Survey of the distribution of Phytophthora cinnamomi in bushland of the Hawkesbury Nepean Catchment Management Authority Area (11 pp. - 663 KB MSWord document).

Project in Sydney Metro Catchment Management Authority, 2008

In association with the Royal Botanic Gardens & Domain Trust the Sydney Metropolitan Catchment Management Authority (CMA) funded a project to survey the distribution of Phytophthora Dieback in the Sydney region and develop guidelines for Phytophthora Dieback Management - Best Practice Management Guidelines for Phytophthora cinnamomi in the Sydney Metropolitan CMA, survey of the distribution of Phytophthora cinnamomi within the Sydney Metropolitan CMA and a report: 'The susceptibility of selected NSW plant species to Phytophthora cinnamomi' are all available. Although these guidelines were developed for the Sydney Metro CMA the practices can be adopted for the management of Phytophthora Dieback in other areas of NSW.

Be sure to include in your plan the additional information and resources in Managing Phytophthora Dieback.

Project in Hawkesbury-Nepean Catchment Management Authority, 2008

In association with the Royal Botanic Gardens & Domain Trust the Hawkesbury-Nepean Catchment Management Authority (CMA) funded a project to survey the distribution of Phytophthora Dieback in the CMA and develop guidelines for Phytophthora Dieback Management - see CMA site for Best Practice Guidelines, and maps and other reports produced. Although these Guidelines were developed for the Hawkesbury-Nepean CMA the practices can be adopted for the management of Phytophthora Dieback in other areas of NSW.

Be sure to include in your plan the additional information and resources in Managing Phytophthora Dieback.

Project Dieback Blue Mountains World Heritage, 2009

Zoe-Joy Newby, is a PhD student of the University of Sydney based at the Royal Botanic Garden Sydney. Zoe-Joy's project is to better understand the role of Phytophthora in vegetation dieback in the Greater Blue Mountains World Heritage Area (GBMWHA) and to facilitate better-informed policy and decision-making and risk management by assessing the level of threat that this pathogen is posing to the GBMWHA. A map and risk model will be developed as a tool to assess the level of threat and being expressed on a spatial level it will assist in assigning priority to disease management and enable monitoring to assess effectiveness of management.

Helping with soil sampling

Part of the project is to survey the area for Phytophthora cinnamomi, by examining soil throughout the area. This is a very big area and will only be achieved by help from Parks and Wildlife Service staff and community volunteers.  If you are able to assist with collecting soil samples in the Greater Blue Mountains World Heritage Area please contact Zoe-Joy at diebackproject@bmwhi.org.au.

Phytophthora Dieback Education Project 2010

The Royal Botanic Gardens & Domain Trust received an Environmental Trust Dissemination Grant to conduct some general awareness and educational work to raise the understanding of and reduce the spread across NSW of Phytophthora, a root rot pathogen, which causes Phytophthora Dieback. The project was managed by Dr Edward Liew, Plant Pathology Manager, and conducted by Patricia Meagher, employed as the Phytophthora Education Coordinator. During the project two brochures, a magnet and poster were developed for a range of audiences, substantial updating of this website and three workshops for land managers were conducted on the impacts of the pathogen and ways to minimise its spread.  The development of the five strategies approach to managing Phytophthora Dieback was a key outcome of this program. This approach can be used as a template to managing any disease or pest. 

Phytophthora Dieback kills plants and infection is permanent. The pathogen attacks the roots of plants, travels in water and along root systems and is spread in contaminated soil. This can be via small amounts of soil attached to shoes of walkers up to large soil disturbances during major earthworks. Highly susceptible plants die quickly but even those that are not highly susceptible will succumb during long periods of dry weather. The loss of root mass limits the amount of water and nutrients a plant can absorb, leaving it susceptible to insect attack, other plant diseases and drought stress. The pathogen poses a significant threat to ecosystems functions by altering and reducing species composition and structural form of the vegetation. Native birds and animals, invertebrates and microflora may all be threatened by these changes in vegetation. 

There are only three management objectives for Phytophthora Dieback

  • keeping areas free of infection
  • limiting the spread and
  • managing infected sites using
    • hygiene
    • quarantine and
    • treatment of infected plants.

Firstly, we developed a five strategies approach to manage Phytophthora Dieback in bushland. The strategies are

  1. Understand Phytophthora Dieback
  2. Assess for risk of disease
  3. Adjust work practices to reflect risk
  4. Inform all staff, contractors and visitors 
  5. Treat infections. 

We summarised this into an easy 5-point approach for land managers and published a brochure covering these points.

We've also produced a postcard sized leaflet for a general audience, explaining how it is spread and the simple actions required to halt the spread. The main message here is 'Don't be a Carrier' by starting out clean and staying clean. As mud sticks more easily, avoid wet and muddy areas and clean not just your shoes, but anything that picks up soil, such as walking sticks, tent pegs and of course off-road bikes and car tyres.

Infection is permanent, so a constant and concerted effort is needed from all of us to keep it out, limit its spread and reduce the impact of this killer. Please spread the message - not the Dieback!

6521microfungi.gif
Phytophthora cinnamomi hyphae

Xanthorrhoea
Xanthorrhoea with Phytophthora Dieback

BGT-map
Hawkesbury Nepean 2008 survey map

CMA-map
Sydney Metro CMA 2008 survey map.