Restoring the canopy health of declining native trees

The rapid decline in health of native trees across the south-west of WA over recent years is causing great concern. Over the past two years we have had many enquiries from landholders about the cause(s) of decline of their trees, and whether there is anything they can do to alleviate this decline. The loss of old, significant trees can be devastating for the landholder, not to mention for the associated flora and fauna reliant upon these iconic and dominant canopy species. Most of our enquiries concern marri, tuart, jarrah, WA peppermint, flooded gum and banksia. If people see jarrah or banksia declining or dying they often assume Phytophthora to be the cause, or if they notice marri declining, they assume it is the marri canker. It is always very dangerous to assume though, as mis-diagnosis is very common indeed and we have observed many examples where sudden death of jarrah or banksia has not been due to Phytophthora. The role of the forest pathologist is to consider all the factors that may predispose, incite or contribute to a decline in health of a specimen, and there can be many factors to consider. A change in climate or increasing age can predispose trees to decline, factors such as pathogens, pests, drought or a frost event may incite the decline, and over time, other contributing factors like canker fungi and pests can increase the severity of this decline to a stage where the tree can no longer naturally recover and will eventually die