Journal of the Royal Society of Western Australia, 87(1), March 2004 
western Avon Wheatbelt bioregion covering the 
Department of Conservation and Land Management's 
(CALM) Narrogin operational district, approximately 
east of the 600 mm rainfall isohyet on the Darling Plateau 
(Fig 1). The area contains a number of nature reserves 
and the system of State Forest blocks that make up the 
Dryandra State Forest This work was undertaken to 
identify P. cinnamomi disease infestations and limit the 
risk of disease spread within the district. The impact of 
the disease and the species affected is also discussed. 
Materials and Methods 
Linear survey method 
Due to the large size of the study area the 'linear 
survey' method (Anon 2001) was used to detect the 
disease symptoms caused by Phytophthora cinnamomi 
infestations. This involved slowly driving (less than 25 
kmh 1 ) or walking all accessible tracks within the forest 
block or nature reserve being considered, including 
boundary tracks along private property. Areas were 
mapped according their 'interpretability' for 25 m either 
side of the track. This technique is based on the premis 
that as an introduced pathogen, occurrence will generally 
be related to past disturbance or access routes. 
Tnterpretable' areas are those that have susceptible 
species in sufficient numbers to indicate whether the 
presence of P. cinnamomi can be adequately assessed 
(Anon 2001). 'Uninterpretable' areas are those where 
susceptible species are absent or too few in number to 
determine to the presence or absence of the disease. The 
boundaries of categories were marked using a handheld 
global positioning system unit (Garmin II plus). Sites 
with likely disease symptoms were examined on foot and 
a soil and root sample taken from dead or dying plants 
to confirm the presence of P. cinnamomi. 
Soil and root samples 
Fifty soil and root samples were taken from dead or 
dying susceptible plants, to a minimum depth of 30 cm 
(sterilised surface root samples were not taken). Samples 
were taken during April 2000 to May 2002. Axes and 
shovels were used to remove sections of root material 
and collect soil. All equipment used to collect the samples 
was sterilised before and after sampling with Methylated 
Spirits (95% v/v ethanol). 
Sample baiting followed Marks & Kassaby (1974) 
where Eucalytpus sieberi F Muell cotyledons were used to 
determine whether the soil and root tissue samples were 
infested with P. cinnamomi. All samples were processed 
by the Vegetation Health service at CALM. 
Infestation assessment 
The impact at the P. cinnamomi infestations was 
assessed by determining the percentage of susceptible 
species that were dead or dying (see Anon 2001 for a list 
of susceptible species). Low impact refers to sites with 
few deaths; medium impact refers to scattered or <30% 
susceptible species deaths; high impact refers to sites 
with most susceptible species deaths (follows Shearer et 
al. 1997). At the Lol Gray infestation (Table 1, site 1) this 
was quantified using 10 x 10 m quadrats. 
Voucher specimens were collected from dead and 
dying susceptible plant species at the Lol Gray infestation 
site. All specimens were submitted to the Western 
Australian Herbarium for incorporation into the 
collection. 
Results 
Infestations 
Out of the 21 Dryandra Woodland blocks, 11 nature 
reserves and one private property, four dieback 
infestations were located (Fig. 1). All infestations were 
located on water-gaining sites (i.e. along a water course, 
drain or near a dam) or where there had been high 
disturbance in areas that were also low in the landscape. 
The infestation at Lol Gray State Forest in Dryandra 
Woodland was the largest at 16.4 ha (including a 10 m 
buffer). Three of the four infestations had low disease 
impact, while the Lol Gray State Forest, had low to high 
impact sites. 
Susceptible species 
Eleven susceptible plant species were recorded as 
dead or dying in association with the dieback infestations 
(Table 2). Other possible causes of death may include 
drought, roadside compaction of roots, or a combination 
of factors. These causes cannot be ruled out as a 
contributing factor in the deaths of species listed in Table 
2. All are from plant families previously recorded as 
having species susceptible to dieback disease (Shearer & 
Dillon 1995) although six species are new to the 
Phytophthora cinnamomi dieback disease indicator species 
list (Anon 2001). 
Table 1 
Topograhical situation, soils/geology and disease impact for Phytopthora cinnamomi infestation locations. 
Location 
Topographical situation 
Soils/ geology 
Impact* 
1. Lol Gray State Forest (Dryandra Woodland) 
2. Culbin Nature Reserve 
3. Hotham River Nature Reserve (8291) 
4. Hotham River (private property) 
Lower slope beside drainage line and dam 
Flat 
Lower slope beside river 
Lower slope beside river 
Over granite 
Grey sand 
Grey sand 
Grey sand 
Low to High 
Low 
Low 
Low 
* Low impact refers to sites with few deaths; medium impact refers to scattered or <30% susceptible species deaths; high impact refers 
to sites with most susceptible species deaths (follows Shearer et al. 1997). 
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