Myrtle rust, caused by the fungus Puccinia psidii, was first discovered in Australia in April 2010 in a New South Wales nursery. It has now been detected in Queensland, Victoria, Tasmania and the Northern Territory.
Ongoing detections have revealed its presence in commercial nurseries, public landscapes and state forests. It is imperative that myrtle rust is prevented from becoming established in Western Australia.
Threat to the landscape
Laboratory trials have shown that a large number of plant species will succumb to this disease, although it is not yet known how climate differences might influence its spread in WA compared to its spread on the eastern seaboard. In a worst case scenario, myrtle rust could devastate forests and other native habitats. Iconic eucalypts such as jarrah, karri, tuart and wandoo are all at risk as well as the WA peppermint tree.
Myrtle rust could also damage eucalyptus or oil mallee plantations, apiculture, the cut native flower trade and the garden industry, and its spread could affect tourism if natural landscapes were badly damaged.
The visual appeal of streetscapes would be greatly reduced, especially where the council has multi-planted one particular tree, such as red-flowering gum, bottlebrush or paperbark, to create a uniform roadside planting. Native trees in streets and parks provide green corridors through suburbia that provide food, shelter and nesting places for wildlife, so their loss could affect local fauna populations.
Certain plants in domestic gardens are vulnerable to myrtle rust. The first detection in NSW involved a purple-leafed cultivar of the WA peppermint tree Agonis flexuosa ‘Afterdark’ - often grown in the home garden as a small feature tree. Some lilly-pillies (Syzygium species) are also susceptible to the disease, as are other favourite ornamental shrubs including Geraldton wax (Chamelaucium uncinatum), Beaufortia, Kunzea, Verticordia and Calothamnus species.
Home gardens could be protected in the event of myrtle rust occurring, because chemicals (copper oxychloride, triforine, mancozeb, tebuconazole and trifloxystrobin) that control the disease are the active ingredients in several readily available sprays. However, chemical control is not a viable option for large-scale landscapes, native forests and other natural ecosystems.