The risk of extinction resulting from disease caused by Phytophthora cinnamomi to endangered, vulnerable or rare plant species endemic to the Grampians, Western Victoria

Abstract

Seven rare, vulnerable or endangered plant species endemic to the Grampians Ranges (Gariwerd) in Victoria were tested for their susceptibility to Phytophthora cinnamomi Rands. Existing habitats were checked for infestations of P. cinnamomi. Plants were grown from cuttings collected either from nurseries or from the Grampians National Park. Symptoms on inoculated plants and measurements of shoot growth and vigour were recorded weekly. Dry biomass was recorded at the end of the experiment and the pathogen was re-isolated from inoculated plants to confirm disease aetiology. Results from pot trials were correlated with the results from extensive field surveys for each species in its habitat to assess the risk posed by P. cinnamomi to each species' existence in the wild.The pot trials and field observations revealed that the risk of extinction from infection caused by P. cinnamomi was high for Pimelea pagophila and Pultenaea subalpina (both highly susceptible and inhabiting infested sites) as well as for Asterolasia phebalioides seedlings and Borya mirabilis (both moderately susceptible and inhabiting infested sites). The risk from P. cinnamomi was medium for Sphaerolobium acanthos (susceptible) and low for Grevillea microstegia (slightly susceptible). Hibbertia humifusa subsp. humifusa (field resistant) was not at risk. Measures to protect the susceptible species have been investigated and are discussed.