Sage et ah Occurrence and impact of Phtophthora cinnamomi, Avon Wheatbelt bioregion 
Susceptible species observed dead 
Table 2 
or dying in association with Phytophthora cinnamomi infestations in the Narrogin district. 
Species 
Family 
Voucher No. 
Site Impact + 
%* 
Allocasuarina ?huegeliana 
Casuarinaceae 
_ 
High 
100% 
Banksia cuneata # 
Proteaceae 
- 
- 
- 
Banksia prionotes # 
Proteaceae 
- 
Low to medium 
- 
Dampiera lindleyi 
Goodeniaceae 
LWS 1-9 
Low 
11% 
Gastrolobium calycinum 
Papilionaceae 
LWS 1-8 
Low to high 
25- 90% 
Hakea incrassata 
Proteaceae 
LWS 1-6 
High 
25% 
Persoonia qtiinquenervis 
Proteaceae 
LWS 1-7 
High 
14% 
Petrophile serruiae 
Proteaceae 
LWS 1-2 
High 
100% 
Synaphea aff. petiolaris 
Proteaceae 
LWS 1-1 
High 
83% 
Xanthorrhoea drummondii # 
Xanthorrhoeaceae 
LWS 1-3 
Low to high 
50% 
Xanthorrhoea preissii 
Xanthorrhoeaceae 
- 
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). # returned a positive sample for Phytophthora cinnamomi 
when soil and root tissue samples were taken from around the base of plants at suspected infestations. Nomenclature follows 
Paczkowska & Chapman (2000). * within 10 m x 10 m quadrats. 
% refers to dead and dying plants 
Samples 
P. cinnamomi was recovered from five of the 50 soil 
and root tissue samples taken from dead or dying plants 
across the study area,. The infestation at Hotham River 
(Table 1, site 4) had previously been identified from 
samples taken along the Pingelly to Narrogin highway 
(Shearer 1994). 
Discussion 
Shearer (1990,1994) found that Phytophthora cinnamomi 
dieback disease impact is low in inland woodlands and 
shrub lands due to the low rainfall. Three of the four 
infestations located in our study area supported this 
finding. However we found that the level of impact in 
low rainfall areas can also be high, as observed at the Lol 
Gray infestation. At this site, a contributing factor may 
the granite outcropping (Table 1). Granite outcrops 
promote moisture runoff after rainfall or fog events (York 
Main 1997) and possibly there is some under-surface 
moisture accumulation; moisture is a key factor in the 
biology of the disease (Shearer & Tippett 1989). This 
effect may be comparable to the effect of concreted duri- 
crust layers of the jarrah (Eucalyptus marginata Donn ex 
Sm.) forest where zoospores are transmitted laterally 
over the layer (Shea et ah 1983). 
No infestations were observed away from low land 
and/or water-gaining or highly disturbed sites (Table 1). 
In this bioregion it is unlikely that there is sufficient 
moisture throughout the year to sustain an upland P. 
cinnamomi infestation. Kuhlman (1964) found that P. 
cinnamomi was unable to survive in dry soils. When 
screening for P. cinnamomi we therefore recommend 
taking soil and root tissue samples from deep-rooted 
plants such as Banksia spp. Moisture in roots and soil is 
likely to be higher deeper in the soil profile. 
Management recommendations 
1. In winter and spring or under moist soil 
conditions (where clumps of soil may attach that 
may carry propagules) vehicles should be cleaned 
down on entry into reserves and State Forest 
blocks to remove soil and root material 
underneath. 
2. Road maintenance activities should avoid 
relocating soil from gullies and water-gaining sites. 
3. Vehicle access tracks that cross gullies or areas of 
muddy sticky soils should be constructed to allow 
natural drainage. Track running surfaces should 
remain hard and not conductive to soil adhering to 
vehicles. 
Acknowledgements : Thanks to Greg Durell (CALM Narrogin), Janet 
Webster, Nola D'Souza (CALM Vegetation Health Service) and Martin 
Rayner (CALM Bunbury). Funding for this work was supplied by the 
Western Australian Salinity Strategy: Crown Reserve Program. 
References 
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