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Assess for risk of disease

As outlined in the five strategies approach, once you understand the disease then you can assess your risk, looking at such things as your climate, vegetation, soil type, water movement across the landscape, levels of human activity, etc. 

Record data from the site assessment in a way that it can be used to monitor changes in vegetation over time. Assess the risk on a yearly cycle.

(a) Define climatic risk

Phytophthora is likely to be present in warm moist conditions between 15-30°C with rainfall greater than 500 mm a year.

(b) Gather information and quantify risk

Quantify the risk across your site, using information from a survey, and by mapping:

  • vegetation, noting known susceptible plant species and conservation values. Include any historical changes. Over time develop a list of ‘plants at risk’ in your area.
  • plant health, including any changes
  • soil type, taking into account texture, amount of organic matter, pH and drainage
  • movement of water across the landscape
  • levels of human activity
  • results of soil analysis for Phytophthora
  • proximity to infected areas
  • proximity to high levels of human activity

(c) Soil sampling

As all spores and structures of Phytophthora are microscopic, only laboratory analysis of soil is definitive

Sampling soil for laboratory analysis:

  • select an appropriate site, based on disease symptoms
  • use disinfected sampling tools (70% methylated spirits), to ensure you don’t spread the disease while sampling
  • scrape back organic layer above fine roots of plant
  • dig 3-4 holes around plant 10-15 cm deep
  • take a small hand trowel of soil and fine roots from each hole, collecting around two cups per plant
  • mix in a plastic bag, seal and label well and clearly
  • record GPS location
  • do not refrigerate.

(d) Develop a reassessment and monitoring program

Establish a program to reassess sites and monitor changes in risk, including updating maps. Stay informed, and review work practices and education programs. Monitor these for effectiveness and alter where needed.

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