Notes  prepared by Marion Simmons of a presentation to the APST Northern Group on 17 November 2009
Plant die back
Guest speaker at the meeting was Tim Rudman, a botanist with the Biodiversity Monitoring Section in Department of Primary Industry, Parks, Water & Environment working with plant disease issues in native vegetation. In particular he has studied the introduced plant pathogen Phytophthora cinnamoni. Tim gave an extremely informative and important talk on the history of this fungus in Australia, particularly in Tasmania..

Phytophthora cinnamoni
was introduced from south-east Asia, and is commonly known as cinnamon fungus because it was first discovered affecting cinnamon trees. It has moved to different parts of the world killing many different species of plants that have no defence against it. It cannot be seen except by microscope, it attacks roots where it produces enzymes that dissolve plant cells preventing nutrient from making its way to the foliage. Grass trees dying in our heath lands represent a typical response to its presence. Some plants like tea trees can 'wall' it off whereas others like the pea family do not recognise it as a threat. In nurseries damping off can be caused by this pathogen; in gardens a series of native plants can be affected as well as azaleas and rhododendrons (i.e. ericaceaous plants); in Queensland avocado orchards and some members of the Protea family like Dryandras and Banksias and in Western Australia the jarrah forests (Eucalyptus marginata) have been devastated. In Tasmania, Forestry has found that introduced Eucalyptus nitens is subject to attack by the pathogen until 2-3 years old.

Wet or moist soil and warm conditions create the perfect scenario for the pathogen's survival. It produces spores that wait in the drier soil until conditions are damp and it becomes active once more. Spores can be present in dams or in creeks; it is spread by mud on vehicles, heavy machinery, walkers and by animals. Treated water from our water systems is OK to use on plants or gardens, but creek or river water can harbour the pathogen. A Tasmanian distribution map shows this killer disease is present pretty well all round the State except in very dry country and the central plateau where it is too cold and wet and there is little road access. Button grass plain and coastal heath plants are very susceptible to attack.

Phytophthora cinnamoni
attacks about 30 species of native plants and for example, our rare East Coast endemic Epacris are particularly at risk of extinction.

There is no final solution, although Western Australia has spent millions of dollars on possible control measures.

It seems the best methods of control are:
  • controlling access
  • not importing plant material or soil from outside the area
  • washing, using town water or rainwater only, all equipment, tools, vehicles, footwear; improving area drainage
  • using 'Phosphite', a benign chemical that helps some plants to suppress the disease. Unfortunately not all plants respond, e.g. Epacris
  • sterilise the soil and pots before use
  • breed plants that are resistant to the disease
In the plant nursery or garden:
  • raise pots off the ground onto benches and keep separate
  • use organic rich potting mix-no gravel or sand. Quarries are a source of the disease
A sentinel plant like lupin can be grown to signal if phytophthora is present in your soil or soil mix.
Seeds and cuttings are not affected by the fungus and are OK to share with others.