Myrtle Rust

Myrtle rust (Austropuccinia psidii)

Myrtle rust is a plant disease caused by a fungus, Austropuccinia psidii, infecting plants in the Myrtaceae family. The fungus was first detected in South America on common guava and lemon scented gum, and is now considered native to South and Central America.

There are other species of rust in South Africa, South America and Central America, one of these in particular has an affinity for eucalyptus, and has caused considerable damage to plantations in South America.

There is only one species currently present in Australia, it was first detected in NSW on Agonis flexuosa in 2010, and has spread and established itself throughout the eastern coast of Australia, parts of the Northern Territory and marginally in parts of Victoria and Tasmania.

How it spreads

The fungus’ spores can travel by wind, animals, and humans moving plant material around. It is exceptionally mobile, and once an infection establishes it is very hard to remove.

An emergency response was initiated in 2010 when the disease was first detected in Australia, federal and state governments worked with industry groups and property owners to contain the disease. They removed host material, established buffer zones, used fungicide treatments, quarantine controls and host range testing. Ultimately the efforts were unsuccessful, and myrtle rust spread into native bushland and beyond.

The only states without myrtle rust currently are West and South Australia, who do not allow any myrtaceae across the borders. The fungus has proven capable of infecting 382 native Australian species, many of these being within the Eucalyptus, Agonis, Melaleuca, Metrosideros, Leptopsermum and Callistemon genus’.

Figure 1. The yolk-yellow spores of myrtle rust.

What to do if you find it

In Tasmania nurseries and other retailers selling plants are the main avenue where myrtle rust has been detected, with most recorded cases being confined to Lophomyrtus species in residential gardens, and has not been found in local bushland.

The time when you are most likely to see Myrtle Rust is when humidity is high, and temperatures are between 15-25ºC. The leaves being wet for 6 hours or more encourages spore production and spread. If you find myrtle rust in the wild there is a phone number where you can report sightings (NRE Tasmania 1800 084 881), avoid contamination, take a photograph, record the GPS location, the number and species of plants and a description of the infection.

If you find it in your garden, remove and bag the plant material while avoiding contact with the spores, and throw away with your household waste, not in your green waste or compost.

References

Makinson , R., Pegg , G., & Carnegie , A. (2020). Myrtle Rust in Australia – a National Action Plan. Australian Plant Biosecurity Science Foundation, Canberra, Australia., https://www.anpc.asn.au/myrtle-rust/.

Makinson, R. (2018). Myrtle Rust reviewed: the impacts of the invasive pathogen Austropuccinia psidii on the Australian environment. Plant Biosecurity Cooperative Research Centre, Canberra. https://www.anpc.asn.au/myrtle-rust/

Myrtle rust host plants and symptoms. (2022). Agriculture Victoria. Retrieved September 11, 2022, from https://agriculture.vic.gov.au/biosecurity/plant-diseases/shrub-and-tree-diseases/myrtle-rust/myrtle-rust-host-plants-and-symptoms

Myrtle rust (Austropuccinia psidii). (2021). Department of Climate Change, Energy, the Environment and Water. . Retrieved September 11, 2022, from https://www.dcceew.gov.au/environment/invasive-species/diseases-fungi-and-parasites/myrtle-rust

Myrtle Rust. (2022). Biosecurity Tasmania. Retrieved September 9, 2022, from https://nre.tas.gov.au/biosecurity-tasmania/plant-biosecurity/pests-and-diseases/myrtle-rust

Images courtesty of Scot Nelson and The Royal Botanical Gardens of Sydney, with former sourced from Flickr and listed in the public domain.

Images courtesy of Scot Nelson and The Royal Botanical Gardens of Sydney, with former sourced from Flickr and listed in the public domain.