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Phytophthora dieback devastation - Photo © Parks and Wildlife

What is Phytophthora dieback?

  • Phytophthora dieback is caused by the plant pathogen, Phytophthora cinnamomi, which kills susceptible plants, such as banksias, jarrah and grass trees, by attacking their root systems.
  • Dieback is a symptom of a Phytophthora infection, and affects more than 40 per cent of the native plant species and half of the endangered ones in the south-west of Western Australia.
  • The plants die because they cannot take up the water and nutrients they need.
  • It's is not easy to detect as infected plants often appear to be dying from drought.
  • There is no known cure for the disease.
  • Phytophthora disease also affects many agricultural crops and garden plants.
  • The fungus is spread through the movement of soil and mud, especially by vehicles and footwear. It also moves in free water and via root-to root contact between plants.
  • Help prevent the spread of Phytophthora dieback.
  • It can devastate bushland by removing particular plants and changing the nature of the landscape, possibly driving rare species toward extinction. Changes in the composition of bushland also represent habitat change to animal communities with flow-on effects to their survival potential.
  • There are several species of Phytophthora, but Phytophthora cinnamomi is the most widespread and destructive. It was probably introduced by early European settlers in the soil of plants they brought with them.
impact-map small

Spread of dieback in WA
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Its impact in Western Australia

More than 40 per cent of Western Australian native plants are susceptible to the disease, particularly those in state's south-west.

The area of land infected in Western Australia by Phytophthora dieback is equivalent to 500 times the size of Rottnest Island or over one million hectares.

Twenty per cent of the state's jarrah forest and up to 80% of the Stirling Range National Park infected.

Where it is

Phytophthora dieback has been found in many of south-west Western Australia's national parks, nature reserves and metropolitan bushland:

How it affects the environment

Dieback can cause:

  • loss of biodiversity
  • extinctions of threatened plant and animal species that rely on susceptible plants for food and habitat, such as dibblers, western ground parrots and honey possums.
  • reduced variety of native plants
  • loss of key understorey species
  • disruption to woodland vegetation structure
  • the increased dominance of resistant plants such as grasses, rushes and sedges, or introduced weeds.
Dieback shoe cleaning station - Photo © Parks and Wildlife

Stopping dieback

Phytophthora cinnamomi lives in soil and in plant tissue, and can survive in plant roots during the dry summer months.

  • The warm moist soils of the state's south-west provide ideal conditions for Phytophthora cinnamomi to produce millions of spores.
  • The disease is spread through infected soil and mud, especially by vehicles and footwear, as well as through water and root- to root contact between plants.

Managing the disease

There is no known cure for Phytophthora dieback.

The department is carrying out research into the fungicide phosphite, a biodegradable fungicide that protects plants against Phytophthora dieback. Phosphite works by boosting the plant's own natural defences, allowing some susceptible plants to survive in Phytophthora dieback infected areas. 


Prevention is still they key. Limiting the spread of Phytophthora dieback is cheaper and far more effective than managing the impacts of the disease once introduced to a bushland.

Phytophthora dieback is most rapidly spread through human activity resulting in the movement of infected soil on vehicles, equipment and footwear.

Forestry and mining industries, as well as recreational bushland users (such as off-road vehicles, mountain bikes and bush walkers) need to take particular care not to spread the disease.

Management practices to prevent the spread of Phytophthora dieback into uninfected areas include strict hygiene measures such as:

  • cleaning stations to avoid transport of contaminated soil
  • cleaning footwear and washing down vehicles and equipment
  • use of dieback free construction materials
  • seasonal and permanent road and trail closures
  • information signs and education.
Vehicle at washdown station - Photo © Parks and Wildlife

What you can do

You can play a vital role in stopping the spread of Phytophthora dieback:

  • look out for information signs around dieback-affected areas and follow the instructions
  • do not move soil or plant material
  • use clean-down stations and boot cleaning stations
  • stay out of quarantined areas in bushland and forest
  • do not enter disease risk areas during, or for three days after, rain
  • follow local regulations when gathering firewood

Dieback free areas:

  • use clean-down stations to remove or sterilise mud and soil from footwear, equipment and vehicles before entry
  • avoid travel during and after rain, when the soil is damp
  • always stay on roads and tracks
  • apply for permits when required (such as when gathering firewood)
  • be prepared for and observe restrictions on access.

The department's role

Phytophthora dieback research is a major component of the department's work.

Our research includes:

  • detecting and identifying new Phytophthora species in Western Australia
    • monitoring the spread, and rate of spread, of Phytophthora pathogens
    • investigating the genetic makeup and survival capacity of Phytophthora species
  • investigating the susceptibility of Western Australian plants to Phytophthora cinnamomi and other Phytophthora species
    • researching the biology and epidemiology of Phytophthora species in native plant communities
  • investigating ways to reduce the spread of Phytophthora dieback.
    • investigating ways to optimise current control methods including phosphite treatment, and hygiene and quarantine protocols
    • researching the role of fire in managing species susceptible to Phytophthora
    • translocating plant species at risk. This involves deliberately transferring plants from one area to another to help conserve it.
  • seed banking rare and endangered flora that is susceptible to Phytophthora disease. Seed banking offers us an efficient and cost effective way of conserving genetic diversity for future conservation work
  • researching and understanding the long-term impacts of Phytophthora cinnamomi in Western Australian ecosystems.

The department has an active program to detect, diagnose and map the occurrence of dieback on lands managed by Parks and Wildlife. This includes interpreting and mapping areas for Phytophthora dieback prior to disturbance operations to manage or contain the spread of dieback. Visit the department's Vegetation Health Service to identify and detect Phytophthora species.

Links and resources


Articles in this category:

Title Modified Date
About the Vegetation Health Service Wednesday, 28 July 2021 09:31
Phosphite and Phytophthora dieback Friday, 10 February 2017 10:12