Phytopthora; cinnamon Fungus
Phytopthora cinnamomi, otherwise known as cinnamon fungus (and "die-back" in some cases) is a very serious fungus disease in both commercial crops as well as home gardens, and in some forest trees.
It infects the roots of plants and moves quickly through the plant tissue causing a thinning of the foliage, die-back and in many cases, death.
One of the worst aspects of this disease is that it affects a very wide variety of different plants...including many Australian native trees & shrubs, ornamentals, fruits, vegetables, ...there are thousands of different plants known to be susceptible.
There are some resistant species.
Occurrence: The disease is commonly associated with wet soils (and heavy clay sites).
Soils are often a low pH, poorly drained and can become waterlogged in wet seasons.
Susceptibility: Eucalypts belonging to the sub genus Renantherae are susceptible.
Those belonging to the sub genus Macrantherae or Poranthereae are more tolerant.
Prostantheras are susceptible, but Westringias are tolerant.
Avocadoes are very susceptible.
Xanthorrea (ie. Blackboys) are very susceptible.
Many germinating seeds, and new young seedlings, in warm, humid, propagation structures (e.g. greenhouses) are very prone to attack by Phytopthora.
Control: Very few fungicides will have any effect. No pesticides are known which can kill off the fungus. Soil sterilisation can be used to eradicate the fungus in an infected area before planting. Often the best approach is simply to improve drainage in the infected area. Dexon (ie. Le San DX), Terrazol, Koban or Truban are fungicides which will help.
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In Australia: www.acs.edu.au/Courses/General-Horticulture-courses.aspx
In the UK: www.acsedu.co.uk/Courses/General-Horticulture-Courses.aspx