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6 Sep 2022

Plan to tackle threat from devastating myrtle rust fungus

A national survey has been created to help save Australian native species from the devastating myrtle rust disease.

A national living collections database of myrtle rust-susceptible plant species will be created from the survey, open to those across the and Botanic Gardens Australian and New Zealand (BGANZ) network and beyond with species from the family myrtaceae in their collections.

Myrtle Rust affects plant species in the family myrtaceae, which includes iconic Australian species such as paperbarks, tea-trees, eucalypts, guavas and lillipillies - key and often dominant species in many Australian ecosystems.
To date the fungus has proved capable of infecting about 400 native species and this number is likely to grow. Serious declines towards extinction are under way in some species, and broader ecological consequences are expected.

Myrtle rust
How myrtle rust looks. Picture: Scot Nelson

The Australian Government recognises myrtle rust as a key threat to Australia’s threatened species.
Biosecurity funding from the Australian Government’s Department of Climate Change, Energy, the Environment and Water (DCCEEW) is supporting the Council of Heads of Australian Botanic Gardens (CHABG) and BGANZ) to develop the database.
The project will ascertain which species are held in collections across seed banks, botanic gardens, arboreta and their nurseries.
Data from the survey will be used to inform future prioritisation, research and conservation actions for Myrtle Rust-affected species.
The information collected will enable botanic gardens, arboreta, nurseries, seed banks and researchers to use the data to strategically plan and manage their collections, as well as support further research.
The survey results will also be shared with governments, business and the philanthropic sectors so that policy makers and funding bodies have additional information to assist in the prioritisation of future resources.

Myrtle rust
Melaleuca quinquenervia. Picture: Geoff Pegg

Denise Ora, Chair of CHABG and Chief Executive of the Royal Botanic Gardens and Domain Trust, said it was critically important Australia’s ex situ conservation facilities continued to work together to share information, resources and plant material.
“Doing so will give us the very best chance of combatting the threat of myrtle rust to Australia’s native myrtaceae,” she said.
Chris Russell, the Interim Chair of BGANZ, said working with CHABG to deliver the survey meant members could tap into additional expertise and experience of others managing collections in response to the myrtle rust threat.
“We look forward to seeing the data generated through this work supporting further Australian myrtaceae collaborations across our network for many years to come,” he said.

What is myrtle rust?

Myrtle Rust, a highly invasive plant disease caused by the introduced fungal pathogen Austropuccinia psidii, poses a serious and urgent threat to Australia’s native biodiversity.
Arriving in Australia in 2010, the fungus spread rapidly throughout the east coast of Australia and east to New Zealand. It has recently been found in Western Australia.
The disease is spread mostly via wind, but the thousands of spores can also be spread via wildlife, infected plant material, contaminated equipment, clothing and vehicles.
The disease can cause deformed leaves, heavy defoliation of branches, reduced fertility, dieback, stunted growth and plant death.
Widescale management of myrtle rust in the natural environment is untenable, particularly when considering the rate and mode of spread of fungal spores. Furthermore, the significant resources needed to manually treat infected populations to ameliorate fungal infection at scale makes this approach completely unrealistic within current knowledge and resources.
Ex situ (off site) collections of species in botanic gardens, arboreta, their nurseries and seed banks present much smaller numbers of individuals than would normally be found in healthy, functioning populations in the wild (in situ).
These ex situ insurance populations can provide some level of hope for maintaining a species existence at the collection level, particularly when in situ populations are unable to reproduce due to infection.

While ex situ collections usually require an intensive level of management to maintain their health, they also present opportunities for regular monitoring to potentially identify the early signs of infection and improve interventions with timely application of fungicidal treatments.

With current advances in genetic tools, it is also possible to cost-effectively assess genetic variability in the ex situ collections and manage them to ensure we have the best chance of maintaining viable populations.

What next?

The survey was released on August 11 and will be promoted at the 7th Global Botanic Gardens Congress in Melbourne in September 2022 before closing on October 21.
The results will be released at the end of 2022 and will be made freely available to BGANZ members and the public.

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