Extending the host range of Phytophthora multivora, a pathogen of woody plants in horticulture, nurseries, urban environments and natural ecosystems

Abstract

Phytophthora multivora is a recently described species with a global distribution associated with disease of many woody plant species. However, very few pathogenicity studies have been conducted to determine the host range of this pathogen. A soil infestation pathogenicity experiment was conducted using two P. multivora isolates with Phytophthora cinnamomi, a known virulent pathogen, included for comparison purposes. Twenty-seven plant species were included, 19 native to Western Australia (WA) and eight exotic tree species often used as urban street trees. Plants were harvested 12 weeks after inoculation, damage of root systems were rated and root and shoot dry weight measured. Twenty-four out of twenty-seven tested host species were significantly susceptible to P. multivora. P. cinnamomi was often more pathogenic. Despite this, P. multivora represents an ecological risk for urban forests of Perth and for the whole of the South West Botanical Province of WA. Additionally, the susceptibility of other common woody plants found globally in urban environments suggests P. multivora will, in time, become as ‘well-known’ and damaging as P. cinnamomi.