Managing Phytophthora Dieback in bushland is most successful when you have determined whether the disease is present or absent, and if present, identified what parts of the bushland are infested. Management procedures can still be implemented if you are unsure if the pathogen is present. However, without knowing the location of the Phytophthora Dieback, management will not be as effective, it will be difficult to monitor the success of your work, and you may be taking some precautions that are not necessary. Remember that when you have had bushland surveyed for Phytophthora Dieback, the result will only be accurate at that point in time. The disease will spread autonomously and new infections can occur. When planning management procedures for controlling Phytophthora Dieback it is important to re-survey for disease movement and new disease outbreaks every one to two years.
There are two options for determining whether Phytophthora Dieback is present in bushland:
- Engage a professional consultant; or
- Do it yourself.
Professional consultants determine the presence of Phytophthora Dieback by using indicator (susceptible) plants and by testing soil and plant samples. Refer to our Expert Page for the contact details of qualified Phytophthora Dieback interpreters. The consultants listed have undertaken accredited training with DPaW and have many years of experience in completing Phytophthora Dieback surveys.
The cost of a survey will vary, depending on the size and location of the bushland, and the degree of difficulty experienced in interpreting disease symptoms. Consultant fees usually do not include the cost of processing the soil and plant samples (sample processing usually costs between $70 and $150 a sample). Discuss costs with the consultant prior to the work being undertaken.
Community groups can consider applying for funding from various sources to cover the cost of disease surveys. For more information on these potential funding sources contact the Environmental Officer at your local council or the Dieback Working Group.
Do it yourself
You can complete your own disease survey by studying the plants in the bushland. You will need to have a very good knowledge of native plants, various disease symptoms and other causes of plant deaths for the results of your assessment to be accurate and reliable.
The presence of Phytophthora Dieback is determined by observing susceptible plants that are killed by Phytophthora Dieback. 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 disease, for example, Armillaria root rot. If non-susceptible trees, for example red gums, tuarts, flooded gums or wandoo are dying then it is likely that the cause of poor plant health is not Phytophthora Dieback.
Tables 1 and 2 list some common plant species and genera from the jarrah forest and Swan Coastal Plain that are susceptible to Phytophthora cinnamomi, and can be used as Phytophthora Dieback indicator species.
Table 1. Common plants susceptible to Phytophthora Dieback.
|Jarrah Forest||Swan Coastal Plain|
|Adenanthos cygnorum - woolly bush||Adenanthos cygnorum - woolly bush|
|Allocasuarina fraseriana - sheoak||Adenanthos sericea|
|Banksia grandis - bull banksia||Banksia attenuata - slender banksia|
|Banksia littoralis - swamp banksia||Banksia littoralis - swamp banksia|
|Banksia sessilis - parrot bush||Banksia menziesii|
|Eucalyptus marginata - jarrah||Conospermum stoechadis - smoke bush|
|Isopogon sphaerocephalus||Banksia nivea - couch pot dryandra|
|Leucopogon verticellatus - tassel flower||Banksia sessilis - parrot bush|
|Macrozamia reidlei - zamia palm||Hibbertia hypercoides|
|Patersonia rudis - hairy flag||Isopogon formosus - cone flower|
|Persoonia elliptica||Lomandra odora - tiered mat rush|
|Persoonia longifolia - snotty gobble||Macrozamia reidlei - zamia palm|
|Xanthorrhoea gracilis - slender grasstree||Verticordia nitens|
|Xanthorrhoea preisii - grasstree||Xanthorrhoea species - grasstree|
Table 2. Plant genera with species known to be affected by Phytophthora species - including P. cinnamomi (CALM, 1999b)
* many species in the genus are severely affected.
For a more detailed list of resistant and susceptible plant species please consult the Centre for Phytophthora Science and Management website (www.cpsm.murdoch.edu.au).
As well as observing indicator species, the following vegetation features can be used to indicate the presence of Phytophthora Dieback.
Total deaths - Phytophthora Dieback 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 of susceptible plant species.
- Look for something that could have introduced the disease, for example, a track, road or vehicle activity.
A good quality aerial photograph may assist you to identify dead vegetation, locate the infection edge and map its spread. Aerial photographs can be obtained from the Department of Land Information in WA or your local council.
Try to complete mapping when the soil is dry, or keep footwear free of soil to avoid spreading potentially infected soil.
Like the professional consultants, you can also take plant and soil samples and have them tested in a laboratory (refer to Expert page for a list of diagnostic laboratories). Sample results that are positive for Phytophthora Dieback means that the disease is present at the site. Negative results don't mean that the site is free of the pathogen, as it may simply have been missed when the sample was taken. The chance of a positive sample being recorded can be significantly increased if the tissue sample is collected from a plant that has a lesion (decaying tissue) present underneath the bark at the base of the main trunk.
You will need to get instructions from the 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.