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Visitors to the South West will be familiar with big expanses of dead and dying trees and shrubs.

Most of us probably put this down to lack of rain or perhaps bushfire but it is actually a soil-borne pathogen, Phytophthora cinnamomi (Phytophthora dieback) which affects 40 per cent of the native plant species in the South West of Western Australia.

It is the single biggest threat to one of the world's 34 International Biodiversity hot Spots - the only hot spot in Australia.

For many years, government and industry programs have successfully used the fungicide phosphite to reduce the spread and impact of Phytophthora dieback, but it has its own potential problems. A group in the School of Plant Biology is working to understand how phosphite works, in the search for an alternative treatment.

Research Assistant Professor Stuart Pearse and Research Associates Dr Ricarda Jost and Dr Xuanli Ma are members of a larger group of researchers at UWA and Murdoch University which has an ARC Linkage grant with industry partners to study Phytophthora dieback, the effects of phosphite treatment and the sensitivity of native plants to phosphorus.

"While phosphite is currently the best tool for managing the impact of Phytophthora dieback in native plant communities in WA, we think that applications of phosphite may inadvertently be disrupting the natural balance of phosphorus in the soil," said A/Professor Pearse.

"Our natural environment is particularly sensitive to phosphorus. Long-term use of phosphite could have a potential fertilisation effect by increasing the phosphorus in our extremely low-phosphorus ecosystems. This could promote invasion by weeds and other plant species that would otherwise not do well in the ecosystem," he said.

"It could also be impacting negatively on phosphorus-sensitive species. Further experimentation is required to determine if phosphite is having any negative impacts in native plant ecosystems in WA."

A/Professor Pearse said Phytophthora dieback affected nearly 2,300 of the 5,710 native plant species in the South-West botanical province of WA. Its severe disruption of plant community structure causes decline in species richness and abundance, degradation of habitats for animals and changes to ecosystem function and health, making it the most significant threat to landscapes and biodiversity in south-western Australia.

"Its impact has been likened to a biological bulldozer and some botanists have indicated its impact on biodiversity is similar to the last ice-age!" he said.

Phytophthora dieback was recognised in the Environmental Biodiversity and conservation Act 1999 as a major threat to Australia's biodiversity.

Despite that, the Plant Biology group received only 27 per cent of the ARC funding it requested for this project. The importance of this research is demonstrated by the number of enthusiastic industry partners: ALCOA of Australia Ltd, Tiwest, BHP Billiton Worsley Alumina, Western Power and BhP Billiton SSM.

The project is also supported by the Minerals and Energy Research Institute of Western Australia, the Department of Environment and conservation (DEC) as well as UWA and Murdoch University. DEC sprays phosphite aerially over selected biodiversity-rich sites in the Stirling Range National Park, the Fitzgerald River National Park and other areas of the south coast to control and prevent the impact and spread of Phytophthora dieback.

"Plants die quite quickly from Phytophthora dieback," Dr Ricarda Jost said. "Banksias, native grass trees and other highly susceptible ‘indicator' species tend to die first.

"We hope that, by understanding how phosphite works, we will be able to substitute it with something else that doesn't have phosphorus in it, or at least manage the application of phosphite better, perhaps being able to reduce the quantities used," she said.

Published in UWA News , 4 October 2010