Preventing the spread of Phytophthora

Kangaroo Island is a unique region and is home to a diverse range of native plant species. Phytophthora (or ‘root rot’) species are fungus-like organisms, carried in soil and water, that cause disease and death to a wide variety of native plant species, fruits, vegetables and garden plants. There are many species of Phytophthora found in South Australia. Phytophthora cinnamomi, which is also referred to as ‘Pc’, is the most common and destructive species.

What does Phytophthora do?

Phytophthora attacks the roots and stems of susceptible plants and causes them to rot. Once affected, plants are no longer able to take up sufficient water and nutrients, so they die.

What does Phytophthora look like?

Phytophthora is very small and can only be viewed through a microscope. It grows in a thread-like fashion through the roots and trunks of infested plants. The only visible sign of its presence is sickness or death of the plants it attacks.

The first visual symptoms of infection are discoloration (usually yellow or red) of the leaves followed by dieback of the entire plant. Depending on local site and environmental conditions, small shrubs may die within a few weeks and large shrubs and trees may take several years to die.

What can be done to control phytophthora?

There is no cure for Phytophthora once it has infested an area. Phytophthora can spread in ground water and from plant to plant by root contact. It spreads quickly with the help of ‘artificial’ factors, like human disturbance. The best way to control Phytophthora is to prevent transfer of infested soil or plant material.

• Avoid driving, riding or walking in areas when soils are wet and sticky.
• Stay on designated roads and tracks. Vehicles, bikes and people moving off roads into infested areas may pick up infested soil and transfer it to uninfested areas.
• Brush soil off vehicles, bikes, boots and camping gear before entering an uninfested area and after leaving an infested area – don’t wait until you get home to clean them.
• Obey road signs. Roads and tracks may be closed, sometimes permanently, to help stop the spread of Phytophthora.
• Use wash down or hygiene stations when provided.
• Ensure that any plants you purchase for your garden or landscape are free of Phytophthora.

Report any unusual deaths of groups of susceptible native plants you notice on the island to the ki.landscapeboard@sa.gov.au.

Phytophthora fieldwork hygiene protocol 2021 (guidelines)

Suspected locations of Phytophthora on Kangaroo Island (map)