The occurrence and impact of Phytophthora cinnamomi in the central-western Avon Wheatbelt bioregion of Western Australia

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 deeprooted 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.