What is Dieback? 

Susceptible Species

Over 40% or 2300 species of native Western Australian plants are susceptible to Phytophthora dieback. Some of the region's most iconic plant species are susceptible, including Jarrah, Banksia, Dryandra, Hakea, Hibbertia, grasstrees and zamia palms. Over 50% of the Western Australia 's rare or endangered flora species are also susceptible. Many of these plants are only found in south-west of the state. A large number of horticultural crops and garden plants are also susceptible to Phytophthora dieback including apple, peach, apricot and avocado trees, radiate pine, camellias, azaleas, roses, proteas and rhododendrons.

How can I recognise Phytophthora dieback in bushland?

The presence of Phytophthora dieback is determined by observing susceptible plants that are killed by Phytophthora cinnamomi . These susceptible plants are called "indicator species". Jarrah, banksia, grasstree, zamia palm, dryandra and hakea are commonly-used indicator species. You must be able to discount other factors that could have caused the plant death, such as fire, insects, flood, drought, nutrient deficiencies or toxicities, and other plant diseases, for example, Armillaria root rot.

Please note that a number of Western Australian native plants are resistant to Phytophthora dieback, but may be having disease issues due to water stress, toxicities or other plant diseases. These plant species include Red Gums, Tuart's, Flooded Gum, Wandoo and Karri trees.

Download the Department of Environment and Conservation Indicator Species list.

• The Resistant Species to Phytophthora cinnamomi; and 
• The Susceptable Species to Phytophthora cinnamomi.

Download a CPSM gardening brochure.

For a list of south coast species susceptible to Phytophthora dieback, please go to www.dieback.net.au.
As well as observing indicator species, the following vegetation features can be used to indicate the presence of Phytophthora dieback.

• Total deaths. P. cinnamomi kills most plants completely and quickly. Most plants do not die one branch at a time, and there is usually no chance of recovery. For example, an infected banksia often suffers from a sudden death. In contrast, Jarrah trees may look sick for a number of years before suddenly succumbing.
• Lines, groups or localised areas of plant deaths are more likely to be caused by Phytophthora dieback than odd scattered individual plant deaths in otherwise healthy vegetation.
• Look for an edge effect. Edge effects are most obvious when there is a clear distinction between healthy and diseased vegetation.
• Look for old deaths and recently killed plants, that is, an ‘age range' in the deaths. This is because Phytophthora dieback moves from plant to plant over time, killing each plant as it goes.
• Look for signs of the disease in a range susceptible plant species.
• Look for something that could have introduced the disease, for example, a track, road or vehicle activity.

Although it is possible to spot signs of Phytophthora dieback in bushland, the presence of the disease can only be definitively demonstrated isolating the pathogen from a soil or plant tissue sample. You will need to get instructions from the diagnostic laboratory on how to take a sample, the best time to take the sample and how to store and transport it. Sampling usually involves digging up a dead plant to get to the roots. This can be quite a physically demanding task if you are sampling a banksia or grasstree. For a list of diagnostic laboratories please go to the contacts section within this website.