Myrtle rust (Puccinia psidii) is a fungal disease that affects plants of the Myrtaceae family. It is native to South America and was first detected in Australia in New South Wales in 2010 and has subsequently spread far and wide. It is now widespread in the Wet Tropics, where our warm, humid conditions are ideal for germination.
Myrtle rust can spread rapidly because it produces large numbers of small spores that can be dispersed over long distances by wind. It can also be spread by the movement of contaminated plants and soils, on people's clothing and vehicles, or by animals such as bats and bees and possums which come into contact with spores. It has the potential to infect large numbers of rainforest and open forest species in the Wet Tropics, with the ability to affect up to 75% of vegetation, including bush-tucker species, and the animals (like insects, birds, cassowaries, and gliders) that depend on them.
Myrtle rust attacks young, soft, actively-growing leaves, shoot tips and young stems, as well as fruits and flower parts of susceptible plants. The first signs of rust infection are tiny raised spots or pustules. After a few days, the pustules erupt into distinctive, fluffy-looking, egg-yolk yellow spores. Left untreated, the disease can cause deformed leaves, heavy defoliation of branches, dieback, stunted growth and even plant death.
You can read more about myrtle rust, its impacts and prevention on the Queensland Government page.
You can also download some myrtle rust workshop presentations from Biosecurity Queensland and the Queensland Herbarium below: