Journal of the Royal Society of Western Australia, 87:15-18, 2004 
The occurrence and impact of Phytophthora cinnamomi in the central- 
western Avon Wheatbelt bioregion of Western Australia 
L W Sage 1 - 2 , P A Blankendaal 1 , A Moylett 1 & K Agar 1 - 3 
! Forest Management Branch, Department of Conservation and Land Management, 
PO Box 1693, Bunbury, WA 6231, Australia El peterb@calm,wa.gov.au El alexm@calm,wa.gov.au 
2 Current address: Swan Coastal District, Department of Conservation and Land Management, 
5 Dundebar Road, Wanneroo WA 6065 E leighs@calm,wa.gov.au 
3 Current address: Department of Conservation and Land Management, 
Locked Bag 104, Bentley Delivery Centre, WA 6983, Australia 
E kellieag@calm,wa.gov.au 
(Manuscipt received April 2003 ; accepted March 2004) 
Abstract 
Dieback, the expression of the disease caused by Phytophthora cinnamomi Rands, has been little 
studied in the lower rainfall areas of the South-West botanical province of Western Australia. Our 
survey of access routes within the Department of Conservation and Land Management's Narrogin 
operational district (in the central-western Avon Wheatbelt bioregion) identified four areas with 
dieback infestations from 21 state forest blocks (forming Dryandra Woodland), 11 nature reserves 
and one private property block. All infestations were restricted to water-gaining sites lower in the 
landscape or those that had been subject to high disturbance. Fifty soil and root tissue samples 
were taken, with 5 returning positive for Phytophthora cinnamomi. Eleven plant species were 
observed to be dead or dying in association with the infestation sites. Banksia spp and other deep- 
rooted species are recommended for soil and root tissue sampling in this region due to their deeper 
root systems being more likely to support the survival of P. cinnamomi in the drier months. To 
avoid the spread of P. cinnamomi , it is recommended that under moist soil conditions vehicles 
should be clean on entry to nature reserves and State Forest blocks, road maintenance works 
should not move soil from gullies, and that vehicle access tracks across boggy crossings should be 
avoided or built to provide a hard, all weather running surface. 
Key words: Phytophthora cinnamomi dieback disease, Narrogin, Avon Wheatbelt, management. 
Introduction 
A soil borne pathogen, Phytophthora cinnamomi Rands 
is a significant threat to the native vegetation of Western 
Australia, with infestation resulting in the deaths of 
susceptible plant species and altering the ecology of plant 
communities (Shearer 1994). Now widespread in the 
higher rainfall areas of the South-West of Western 
Australia, P. cinnamomi is having a major impact on the 
ecology of the jarrah forest (Eucalyptus marginata Donn 
ex. Smith) (Shearer & Tippett 1989) and other vegetation 
communities of the South-West botanical province 
(Shearer 1994). 
While there are a number of studies have examined 
dieback (the expression of the disease caused by P. 
cinnamomi) in the jarrah forest (Shea et ai 1983; Shearer & 
Tippett 1989; Shearer & Dillon 1995), little work has been 
done on the impact and distribution of the disease in the 
lower rainfall areas of the South West botanical province. 
Shearer & Tippett (1989) considered that rainfall 
distribution is partly responsible for the decreasing 
incidence of P. cinnamomi with distance east from the 
Darling Scarp (decreasing in rainfall with distance east). 
This paper discusses the results of a broad scale 
survey of the distribution of dieback in the central- 
© Royal Society of Western Australia 2004 
Figure 1. Location of the study area and infestations located in 
the central-western Avon-Wheatbelt bioregion of Western 
Australia. Shaded areas are State Forest or Nature Reserves; 
the dashed line is the maximum rainfall isohyet for Western 
Australia; crosses with numbers refer to site numbers from 
Table 1. 
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