Specific Disease Studies

Phytophthora

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Content Contributors
Christian Bien Portrait_edited.jpg

Ben Whitten

Learning Objectives

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What biological agent causes Phytophthora?
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Phytophthora cinnamomi is a fungi-like protist which is actually a water mould.

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What are the reservoirs for Phytophthora?
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Phytophthora cinnamomi lives in soil and in plant tissue, and can survive in plant roots during the dry summer months. The warm moist soils of the state's south-west provide ideal conditions for Phytophthora cinnamomi to produce millions of spores.

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What is the transmission method?
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The disease is spread through infected soil and mud, especially by vehicles and footwear, as well as through water and root-to-root contact between plants.

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Typical pathology (signs, symptoms and progress) of Phytophthora
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Phytophthora cinnamomi has a number of impacts on its affected plant. These include;

  • Wilting of leaves

  • Decreased fruit size

  • Decreased fruit yield

  • Collar rot

  • Gum exudation

  • Necrosis

  • Leaf chlorosis

  • Leaf curl

  • Stem cankers

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What is the life cycle of Phytophthora?
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  1. The usual portal of entry is via root tips. 

  2. Zoospores swim through the soil water and attach to the root tip cells of susceptible host plants. 

  3. Following attachment, the zoospores grow long, thin microscopic filaments of cells. 

  4. Bundles of a few filaments form the mycelial threads known as hyphae that release zoospores. 

  5. Once the zoospores have swum and infected a plant, they produce long-lived chlamydospores (which can survive unfavourable conditions), sexual oospores and further sporangia.

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Treatments, prevention and control measures in Australia/globally
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Removing infected trees, shrubs and plants is one way to limit the contamination of Phytophthora cinnamomi to other surrounding plants. Improving soil drainage is one of the most effective way to prevent contraction of Phytophthora, however, standing water or saturating may be inevitable during prolonged rainy seasons. Testing your soil often to measure the pH balance, determine the necessary nutrients and maximising the health of your plants reduces their susceptibility to opportunistic infections. The application of a 3% solution of household hydrogen peroxide to the soil is effective in killing pathogens such as Phytophthora cinnamomi.


A number of things can be done to prevent the spread of Phytophthora:

  • Cleaning stations to avoid transport of contaminated soil

  • Cleaning footwear and washing down vehicles and equipment

  • Use of dieback free construction materials

  • Seasonal and permanent road and trail closures

  • Information signs and education

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