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Understand Phytophthora Dieback

In order to manage successfully, you need to have a good understanding of what it is you are trying to manage. Because the disease Phytophthora Dieback is caused by a living organism, Phytophthora cinnamomi, it’s important that you understand some features of this organism in order to manage it. 

Phytophthora Dieback attacks plants where you can’t see it occurring, at the roots. It travels in soil moisture and along root systems and is spread in contaminated soil. What you can see above ground is:

  • wilting, yellowing and dieback of the plant
  • quick death of susceptible plants
  • greater loss of plants during dry weather
  • decline in diversity of natural ecosystems
  • change in vegetation structure
  • loss of animals dependent on those plants for food and shelter
  • change in the functions of ecosystems.

Even plants 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, plant diseases and drought stress. The spores of Phytophthora can persist indefinitely in an area as resistant spores or protected in the roots of plants, even those that are not susceptible to Phytophthora Dieback.

Disease depends on three essential components: plant host, environment and the pathogen. Phytophthora occurs in areas with rainfall greater than 500 mm per annum. It is most active when the soil is moist and warm. It can also survive for long periods in plant tissue and soil during dry soil conditions.

Favourable soil conditions for the disease are:

  • warm moist conditions between 15-30°C
  • poor drainage and/or open textured soil
  • soil low in nutrients and organic matter.

The only effective ways to combat Phytophthora Dieback are:

  • preventing introduction - keep it out
  • limiting the spread
  • reducing the impact of the disease

For more information on Phytophthora cinnamomi, see Facts about Phytophthora and read about the research of Dr Chris Howard