Identification of Phytophthora cinnamomi Infection in Tasmania
There are many factors that can cause plant death in Tasmanian native vegetation, including drought die off, salinity issues, prolonged water logging and a range of different plant diseases. If plant death is caused by disease such as Phytophthora dieback it is often indicated by the patterns of disease expression in time and space; the combination of affected and unaffected species; and the symptoms of the affected plants. The combination of these factors in the vegetation as a whole can be used to identify likely Phytophthora dieback, however conclusive identification of Phytophthora cinnamomi as the cause of disease requires laboratory analysis of soil or root samples.
Indicators for recent or active Phytophthora dieback
- Death or disease in known susceptible species (note: not all individual plants will be attacked simultaneously in a diseased area)
- Diseased plants show discolouration of the foliage (usually all the foliage at once), most commonly reds and yellows
- Known resistant species remain healthy
- There is a temporal sequence of disease across a site (e.g. the oldest death in the centre or towards the uphill end of infections on slopes)
- Sharp disease fronts or boundaries between healthy and diseased vegetation may be present
The common indicator species for P. cinnamomi in Tasmania, including the susceptible species and resistant species can be downloaded here:
Indicator species for identification of Phytophthora cinnamomi infections - Tasmanian (124Kb)
Other factors to be aware of
- The age of P. cinnamomi infection and degree of disease activity will affect the ability to successfully interpret the presence of Phytophthora dieback at a site. Careful observation is required to identify old or inactive infected sites, particularly if many susceptible plants have disappeared.
- Mature trees in Tasmania are not usually susceptible to Phytophthora dieback. However numerous other tree mortality syndromes have been killing trees in Tasmania in recent years, at least some of these are related to the changing climate and associated extreme weather events.
Conclusive identification of Phytophthora cinnamomi infections
Morphological identification by an experienced plant pathologist following the collection of soil and root samples is the only way to identify Phytophthora cinnamomi beond doubt. Plant Diagnostic Services, part of Biosecurity Tasmania can undertake this work, and other commercial providers may also be able to on enquiry.