Phytophthora (pronounced fy-TOFF-thora) is a devastating plant killer causing Phytophthora Dieback disease and infection is permanent. It is a soil borne water mould which spreads naturally in water or roots. It is spread much faster and further by humans moving even small amounts of contaminated soil or plant material.
It was once thought to be native to NSW or introduced such a long time ago that indigenous plants had developed resistance to it but this is now known not to be the case (see C. Howard's work). It is true that Phytophthora Dieback presents itself differently in different vegetation types than it does in other states of Australia, but it is no less of a threat to the natural ecosystems of NSW. The pathogen attacks the roots of plants, travels in water and along root systems and is spread in contaminated soil. This can be via small amounts of soil attached to shoes of walkers up to large soil disturbances during major earthworks. Highly susceptible plants die quickly but even those that are not highly susceptible will succumb during long periods of dry weather. The loss of root mass limits the amount of water and nutrients a plant can absorb, leaving it susceptible to insect attack, other plant diseases and drought stress.
The pathogen poses a significant threat to ecosystems functions by altering and reducing species composition and structural form of the vegetation. Native birds and animals, invertebrates and microflora may all be threatened by these changes in vegetation by destroying the food and shelter on which they depend.
There are only three management objectives for Phytophthora Dieback:
- keeping areas free of infection
- limiting the spread and
- reduce the impact, by managing infected sites using
- quarantine and
- treatment of infected plants.