Phytophthora spp.

A soil-borne, fungus-like pathogen (technically it's an oomycete or water mould) that causes the roots to rot. As the roots die off, whole branches, or even the entire tree or shrub, will start to die back. In Auckland it often affects griselinias and avocadoes, though many other trees and shrubs can also be affected. Most commonly affects plants late summer/early autumn.

Prevention

Prevention is far better than cure with root Rot.

Root rot most commonly becomes a problem after trees have been water stressed. Keep plants well watered over the drier months of the year. Water slowly allowing the water to sink down into the roots, rather than allowing it to run off the top of the soils surface

Improved soil health also acts as a preventative, as healthy soil holds more moisture during the drier months and is full of beneficial microbes that make it less likely that you will get root rot. Add Saturaid into the soil at planting as this will help channel the water deep down into the root zone.

Improve soil health by feeding with Aquaticus Garden Booster (which contains trichoderma, a fungi that helps protect roots), and mulch regularly. Improve heavier soils using Gypsum to improve drainage and adding sheep pellets and compost to the soil while planting.

Treatment

Cut out any dead branches and then drench the soil with Plantmate

Plantmate contains trichoderma, a beneficial fungi that colonises around the roots of plants, stimulates root growth, and acts as a fungicide that protects the roots from phytophthoras and other soil-borne diseases.

Spray the plant with Buxus Blight Fighter onto the leaves and around the base of the affected plants.

Repeat 28 days later if necessary.

Wait 2 months and re-apply Plantmate to protect your roots from further incursions. Repeat 1 month later to ensure that the trichoderma in the Plantmate has effectively colonised around the plant roots.

Note: If you catch this too late, treatment may not be effective. If you're unsure bring an image into store or ask our online expert for some advice.