The invasion of native forest by Phytophthora cinnamomi. I. Brisbane Ranges, Victoria

Abstract

Disease within an open sclerophyll forest dominated by Eucalyptus species of relatively low stature (15-20 m) was shown to be caused by Phytophthora cinnamomi Rands, an introduced root pathogen. Diseased sites were mapped and measured. The rate of advance of the pathogen over a period of 5 months was calculated at 4 m per month through moderately drained soils compared with 7 m per month through soils subject to waterlogging. Areas showing disease symptoms increased from 10.8 to 90%, the major extensions occurring along gullies. Spread of the fungus was associated with road-making activities, waterlogging, and the presence of drainage channels. Symptom expression in the different species was studied and shown to be similar to that associated with water stress. Most of the 42 species comprising the woody flora were susceptible to the disease, those particularly susceptible including the dominants. During a period of 8 months mortalities occurred in 50% of the species. Grasses, sedges, and Eucalyptus goniocalyx appeared to be field-resistant, but were uncommon in the Aora of the sites studied.