State of the Environment Report 2007
Phytophthora dieback (also known as 'dieback' or 'jarrah dieback') was first observed in WA in about 1921 as unexplained death of shrubs and jarrah trees. It is believed to have been introduced with horticultural plants soon after European settlement in the South West (Government of Western Australia, 1998). The common name, jarrah dieback, is misleading as the disease affects a very wide range of plant species. The term dieback also refers to vegetation decline caused by salinity, drought, insect damage and other pathogens in other parts of Australia. It was not until the mid-1960s that the causal relationship between large scale tree decline and death and the pathogen Phytophthora cinnamomi was established. Originally the Phytophthora dieback organism was thought to be a fungus but it has subsequently reclassified as a water mould (Dieback Working Group, 2000). The pathogen has been listed as one of the worst 100 invasive species in the world.
Phytophthora dieback represents a serious threat to native flora and biodiversity in the South West. The organism lives in soil and can invade plant roots, causing decay and reducing the plant's ability to absorb water and nutrients and resulting in the eventually death of plants. The infection can spread naturally through movement of soil through water by animals disturbing soil, or from root-to-root contact between affected and healthy plants. Human activities, including road construction, earth moving, livestock movement, wood harvesting and the movement of people and vehicles across infected areas can distribute the disease rapidly across a wide area.
The presence of Phytophthora dieback is not obvious until plant death has started and the foliage begins to turn yellow or brown. Some plants die very rapidly, while others undergo a general decline as the foliage recedes down the tree. The infection can destroy whole ecological communities, also preventing the regrowth of many plant species and reducing available habitat for animals (Department of Conservation and Land Management, 2003c). Some garden, orchard and plantation species are also susceptible. Unfortunately there is no cure for plants once they are infected, and no way of preventing spread through the soil via water flow. The only treatment (phosphite) provides a boost to the plant's immune system but does not eliminate the disease, and requires on-going labour intensive treatments over time to be effective.
Phytophthora dieback is known to occur in forested areas of the South West between Jurien and Esperance (Figure B5.1). P. cinnamomi is found throughout the landscape in areas receiving above 800 mm of rainfall annually, and is confined to stream systems and road verges where annual rainfall is between 600-800 mm. Where rainfall is less than 600 mm, P. cinnamomi is restricted to low-lying areas which can fill with water, or sites that have been altered and receive excessive drainage. There is no record of P. cinnamomi in regions receiving less than 400mm annual rainfall (Department of Conservation and Land Management, 2004a).
A total of 720 000 ha of land in the South West has been intensively mapped for dieback. Of this at least 170 000 ha (24%) were found to be affected. This figure is an underestimate because many of these areas were mapped some years ago, and the disease is likely to have spread since then (Department of Environment and Conservation, 2006b).One of the worst affected areas in the State is the Stirling Range National Park near Albany - 65% of the park is currently affected by Phytophthora dieback. In the South Coast region 800 000 ha have been remotely surveyed for Phytophthora dieback and 58% (465 000 ha) appears to be infested by the pathogen.
![Figure B5.1: Known Phytophthora dieback occurrence in Western Australia. [Data source: Department of Conservation and Land Management [ver. 2006]. Presentation: Department of Conservation and Land Management. Note: Dieback data was compiled from various sources dating from 1976 to 2001, and it has not been updated to show spread from original mapping sites.]](/site/files/images/Figure-B5.1_Large.jpg)
About 14% of South West flora species are highly susceptible to infection by P. cinnamomi, and 40% of species are considered susceptible (Shearer et al., 2004). This equates to 2284 susceptible plant taxa, including 800 that are highly susceptible (of the 5710 described taxa in the South West described in 2004). Of the State's threatened flora, 49% are susceptible to the pathogen (Shearer et al., 2004). Phytophthora dieback is the primary extinction threat to the critically endangered Montane Thicket of eastern Stirling Range threatened ecological community, and threatened flora species including the feather-leaved banksia (Banksia brownii), Fairall's honeysuckle (Lambertia fairallii), Dryandra montana, Lambertia echinata subsp. echinata and Lambertia orbifolia subsp. orbifolia (D Coates, Department of Conservation and Land Management, pers. comm.).
Animals threatened by changes to plant communities caused by Phytophthora dieback include the woylie (Bettongia pencillata), honey possum (Tarsipes rostratus), dibbler (Parantechinus apicalis), mardo (yellow footed antechinus; Antechinus flavipes), Gilbert's potoroo (Potorous gilbertii), western spinebill (Acanthorhynchus superciliosus), ground parrot (Pezoporus wallicus), western bristlebird (Dasyornis longirostris), western whipbird (Psophodes nigrogularis nigrogularis) and many invertebrates (comp. Carter, 2004; Garkaklis et al., 2004; D Coates, Department of Conservation and Land Management, pers. comm.).
There are no eradication methods for P. cinnamomi. This means that the only way to address the existing problem is to prevent its spread and manage impacts in affected areas. This may involve quarantining infected areas with hygiene procedures such as thorough washing of machinery, vehicles or footwear prior to leaving infected areas or entering uninfected areas. Alternatively it may involve limiting forest-related activities (e.g. tourism, wood harvesting, road construction) to dry soil conditions and limiting access to infected areas by fencing, signage, upgrading tracks or restricting access.
Direct application of the chemical phosphite is useful for helping to protect susceptible vegetation from P. cinnamomi. Phosphite is a biodegradable fungicide that helps to improve a plant's immune system. Phosphite needs to enter a plant's water system to be effective, and this can be done by injection or spraying the foliage or trunk of understorey plants. Phosphite is not toxic to people or animals and has a very low pollution risk. Phosphite only provides temporary protection against P. cinnamomi, so treatment needs to be ongoing. Existing application methods are labour intensive, require human access to infested areas and cannot be conducted on a large scale.
Options for the restoration of areas with serious environmental damage through P. cinnamomi infection, or for the successful translocation of threatened flora, are limited. If a species is susceptible to Phytophthora dieback, its long-term survival options are limited to phosphite application and ex situ conservation and research. This could include research on germination processes, site establishment and collection, and possible reintroduction to suitable sites.
The Department of Environment and Conservation undertakes an annual phosphite-spraying program over 164 ha across the South West and protects 17 critically endangered species of native flora and two threatened ecological communities (Department of Environment and Conservation, 2006b). An infested area in the Fitzgerald River National Park is currently being fenced and being subjected to a range of experiments to try to contain the pathogen (such as using high intensity phosphite applications and by controlling surface and subsurface waterflows).
Dieback Consultative Council: The Dieback Consultative Council was created in 1997 to provide advice on Phytophthora dieback matters to the Minister for the Environment. It includes representatives from the community, government agencies, industry and tertiary institutions and helped to develop the Dieback Response Framework. The Council also identifies research priorities and funding and the raising of public awareness of the issue.
Dieback Working Group: The Dieback Working Group is a community organisation which aims to raise public awareness and understanding of Phytophthora dieback in Perth and the South West, encourage the adoption of dieback prevention and management policies and encourage the implementation of management procedures to minimise the spread and impact of the pathogen.
Dieback Response Framework: is a whole-of-government framework being implemented for the management and control of Phytophthora dieback. Actions include the development and release of a Phytophthora dieback atlas for WA; developing a whole-of-government policy on Phytophthora dieback management; developing guidelines for private and local government land; and developing a generic Phytophthora dieback risk assessment methodology for broad community use.
Dieback Response Group: The Dieback Response Group began in 2004 and comprises representatives from the Dieback Consultative Council, Murdoch University's Centre for Phytophthora Science and Management, the Dieback Working Group, the Department of Environment and Conservation, and the Conservation Commission. The group is progressing implementation of the Dieback Response Framework and monitors its progress. It has recently published an atlas of known Phytophthora dieback occurrences in WA (Department of Environment and Conservation, 2006b). A website was recently launched to bring together all the groups working in Phytophthora research, management and policy, and provide an easy way for people to access information about the disease.
Dieback guidelines: The former Department of Conservation and Land Management's Threat Abatement Plan for Phytophthora cinnamomi and Best Practice Guidelines for the Management of Phytophthora cinnamomi provide guidance on how to manage and prevent the spread of Phytophthora dieback (Department of Conservation and Land Management, 2004b; 2004c).
On-ground management: Department of Environment and Conservation is responsible for coordinating Phytophthora dieback activities including the detection, diagnosis and mapping of the occurrence of P. cinnamomi, preparing disease management plans for all uninfected areas, and an annual phosphate spraying program. Community groups such as the Friends of Lightning Swamp Bushland and the Roleystone Dieback Action Group undertake on-ground management and awareness-raising.
The Saving Our Species program began in 2006 and its projects include radical treatment of an infestation in the Fitzgerald River National Park, strategic and operational mapping of Phytophthora dieback and risk assessment modelling in partnership with regional natural resource management groups, and increased application of the chemical phosphite to protect threatened plants in Stirling Range National Park and in areas around Albany, Esperance, Busselton and the Walpole Wilderness Area.
Biodiversity Conservation Strategy: The Department of Environment and Conservation has released A 100-year Biodiversity Conservation Strategy for Western Australia: Blueprint to the Bicentenary in 2029. Public submissions were requested and a final biodiversity conservation strategy is in preparation (Department of Environment and Conservation 2006a).
Natural Heritage Trust/National Action Plan for Salinity and Water Quality (NHT/NAP): These are two Commonwealth Government programs that aim to ensure environmental (on-ground) improvements occur via a targeted strategic approach at the regional level. The Swan, South West, South Coast and Northern Agricultural catchments councils are undertaking projects to manage the spread of Phytophthora dieback in their regions.
Threat abatement plan: Phytophthora dieback is listed as a key threatening process under the Environment Protection and Biodiversity Conservation Act 1999 (Commonwealth) and a threat abatement plan has been completed.
Research: Murdoch University's Centre for Phytophthora Science and Management is providing research on the biology of P. cinnamomi, management of the disease, ecosystem restoration and detection, diagnosis and mapping of the disease.
The death of native plants caused by Phytophthora dieback reduces the biodiversity of the South West and has the potential to cause extinction of threatened flora and fauna. Community amenity and aesthetics are lost when local bushland, backyards and gardens become infected. Public access and enjoyment of national parks are lost if they are forced to close or restrict access to some areas to contain disease spread. There is also the cost of 'cleaning up' dead trees, ensuring public safety, and rehabilitating areas damaged by Phytophthora dieback. Phosphite treatments are not a cure and must be repeatedly applied to postpone onset of the disease, making it an expensive and unsustainable long-term solution (comp. Carter, 2004). The cost of Phytophthora dieback treatment and prevention on former Department of Conservation and Land Management administered land was estimated at $1.6 million in 2005 (Department of Conservation and Land Management, unpublished data) and control is currently undertaken only in very small areas. Phytophthora dieback is also a major economic cost for the mining, horticulture, floriculture, wood production and tourism industries. The estimated economic losses from Phytophthora dieback are $200 million per year (Hardham, 2003).
5.19 Develop and implement an effective whole of government policy to reduce the spread of Phytophthora dieback (including an investment strategy).
5.20 Expand specialised control in areas of high biodiversity value (e.g. threatened ecological communities and the Fitzgerald River National Park).
5.21 Expand research into more effective control methods for Phytophthora dieback, while also continuing research to find a method of eradication.
