How to Identify Phytophthora cinnamomi Infection in Tasmania

There are many diseases which occur in native vegetation and the majority of these are natural events which play an important ecological role. The patterns of disease expression in time and space as well as the species affected and dieback symptoms need to be assessed to identify potential Phytophthora cinnamomi infestations. Conclusive identification of P. cinnamomi as the cause of disease requires analysis of soil or root samples in a laboratory.

Good indicators for recent or active P. cinnamomi are:
  1. Death or disease in known susceptible species (note: not all individual plants will be attacked simultaneously in a diseased area)
  2. Diseased plants show discolouration of the foliage, most commonly reds and yellows
  3. Known resistant species remain healthy
  4. There is a temporal sequence of disease across a site (e.g. the oldest death in the center or towards the uphill end of infections on slopes)
  5. Sharp disease fronts or boundaries between healthy and diseased vegetation may be present

To verify symptom based assessments, soil and plant material should be sampled and analysed for the presence of the pathogen. As P. cinnamomi can be difficult to successfully isolate, expert assistance should be sought when sampling is required.

The age of infection and degree of disease activity will affect the ability to successfully interpret the presence of P. cinnamomi at a site. Careful observation is required to identify old or inactive infected sites, particularly if the majority of susceptible plants have disappeared.

It is also desirable to monitoring a site over a period of time to assist with identifying sites which were inactive but infected at the first visit.
Photograph: disease symptoms in moorland vegetation, Melaleuca.
Colour photograph showing disease symptoms in moorland vegetation, Melaleuca.

This periodicity in disease activity will probably be most evident where host species presence, soil moisture and temperature conditions fluctuate between favourable and unfavourable during or between years.

The following tables list the common indicator species for P. cinnamomi in Tasmania. The susceptible species column presents those species for which mortality is expected within infected areas. The resistant species column lists those species that should remain healthy within infected areas.

Table 1: Table of indicator species for Moorland Vegetation

P. cinnamomi Susceptible speciesP. cinnamomi Resistant species
Agastachys odorataBaumea spp.
Baeckea leptocaulisEhrharta spp.
Banksia marginataEmpodisma minus
Blandfordia puniceaGymnoschoenus sphaerocephalus
Boronia spp.Helichrysum pumilum
Cenarrhenes nitidaLepidosperma filiforme
Dillwynia glaberrimaLeptocarpus tenax
Epacris corymbifloraLeptospermum scoparium
Epacris lanuginosaMelaleuca squarrosa
Melaleuca squameaSporadanthus tasmanica
Sprengelia incarnata
Stylidium graminifolium

Table 2: Table of indicator species for Heathland Vegetation

P. cinnamomi Susceptible species P. cinnamomi Resistant species
Amperea xiphocladaAcacia spp.
Aotus ericoidesAllocasuarina littoralis
Astroloma spp.Comesperma spp.
Baeckea leptocaulisEmpodisma minus
Banksia marginataHypolaena fastigiata
Blandfordia puniceaKunzea ambigua
Boronia spp.Lepidosperma spp.
Dillwynia spp.Leptocarpus tenax
Epacris spp.Leptospermum scoparium
Hibbertia spp.Lomandra spp.
Leucopogon collinusMelaleuca squarrosa
Leucopogon ericoidesPimelea spp.
Melaleuca squameaSpyridium spp.
Persoonia gunnii
Phyllota diffusa
Pultenaea spp.
Sprengelia incarnata
Stylidium graminifolium
Tetratheca spp.
Xanthorrhoea spp.

Table 3: Table of indicator species for Open forest Vegetation

P. cinnamomi Susceptible speciesP. cinnamomi Resistant species
Allocasuarina moniliferaAcacia spp.
Amperea xiphocladaAllocasuarina littoralis
Aotus ericoidesAllocasuarina stricta
Astroloma humifusumBedfordia spp.
Banksia marginataCassinia aculeata
Blandfordia puniceaComesperma spp.
Boronia spp.Exocarpos cupressiformis
Dillwynia glaberrimaGahnia grandis
Epacris spp.Kunzea ambigua
Hibbertia spp.Lepidosperma spp.
Leucopogon collinusLeptospermum scoparium
Leucopogon ericoidesLomandra spp.
Melaleuca squameaMelaleuca squarrosa
Monotoca submuticaOlearia spp.
Oxylobium spp.Pimelea spp.
Persoonia gunniiZieria arborescens
Pultenaea spp.
Stylidium graminifolium
Tasmania lanceolata
Tetratheca spp.
Xanthorrhoea spp.

Tables modified from: Podger, F. Palzer, C. & Wardlaw, T. A. (1990). Guide to the Tasmanian Distribution of Phytophthora cinnamomi and its Effects on Native Vegetation. Tasforests, vol 2, no.1, Forestry Commission of Tasmania, Hobart.

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