What is Dieback? 

What is Phytophthora Dieback?

Phytophthora dieback is a devastating plant disease of native plants, horticultural crops and garden plants worldwide. The introduction of the disease into Australia and particularly south-west Western Australia (WA) is a biological disaster of global significance. The death of native plants decreases the biodiversity of WA's valuable bushland and has the potential to drive rare plant species and their dependant fauna to extinction. The disease is also a significant problem for many industries including mining, forestry, horticulture, nurseries, extractive industries, construction and eco-tourism. It has been estimated that Phytophthora dieback will cost the Australian economy at least $1.6 billion over the next ten years.

Phytophthora dieback is caused by the water mould, Phytophthora cinnamomi (pronounced Fy-to-fora - meaning plant destroyer in Greek). There are over 60 species of Phytophthora, but the species that causes the most severe and widespread damage to native plants in WA is P. cinnamomi .

Is Phytophthora dieback the same disease known as Jarrah dieback?

In the past, Phytophthora dieback has been known as 'dieback' and 'Jarrah dieback'. Unfortunately, these names have contributed to confusion about the pathogen. For example, in other parts of Australia , the term 'dieback' is used to describe tree decline caused salinity, drought or insect damage. The disease also affects thousands of introduced and native plant species other than Jarrah. Therefore, to overcome this confusion, the term Phytophthora dieback is now used.

Impact on Bushland

Phytophthora dieback acts like a Biological Bulldozer in bushland by killing many susceptible plant species. Over 40% (2,300) of the native plant species and half of the endangered plant species in the south-west of WA are susceptible. When Phytophthora dieback spreads to bushland, it kills many susceptible plants, resulting in a permanent decline in the diversity of the whole ecosystem. It can also change the composition of the bushland by increasing the number of grasses and reducing the number of shrubs. Native animals that rely on susceptible plants for survival are reduced in numbers or are eliminated from sites infested by Phytophthora dieback.

It is important to realise that bushland infested with Phytophthora dieback still retains important conservation values. These values include habitat for many native animal species and protection of the landscape from the affects of salinity and erosion. Therefore, it is important to retain and maintain remnant bushland even when it is affected by Phytophthora dieback.