An invasive fungus that attacks some of Australia’s most ecologically important tree species has spread to Western Australia, while also thriving in humid conditions in the east of the country, triggering a “silent extinction” and prompting an urgent call for a national response.
Experts warn that if the myrtle rust fungus detected in eastern Kimberley reaches the state’s biodiversity-rich southwest, the consequences could be disastrous for those ecosystems.
Since the fungus was discovered in a nursery in New South Wales in 2010, it – recognizable by its bright yellow spots and rust on the leaves – has spread all along the east coast and has been found in every state except South Australia.
A 2021 study predicted that myrtle rust could claim at least 16 rainforest plants in an extinction event of “unprecedented magnitude” within a generation.
The fungus affects plants in the myrtaceae family — a diverse group that includes rainforest species, paperbarks, eucalyptus and myrtle. The once widespread native guava has been nearly wiped out by the fungus.
A team led by WA’s Department of Primary Industries discovered the fungus on nine broad- and narrow-leaf paperbarks in eastern Kimberley in late June. The exact species of melaleuca affected is not yet known.
The department investigates tourist hotspots and nurseries, with no new discoveries so far. The potential impacts were “yet to be determined,” a department spokesman said, but the disease can lead to tree death, dieback, species loss and ecosystem degradation.
dr. Louise Shuey, a forest pathologist with the Queensland Department of Agriculture and Fisheries, traveled to the Kimberley to assist with the search.
“Myrtle rust can travel hundreds of miles on the wind, which is why it spreads so far,” she said.
The site was searched after modeling pointed to isolated wetland as a likely site, spreading from infested plants in the Northern Territory eastwards.
Alyssa Martino, a research scientist at the University of Sydney, has begun testing 25 WA melaleuca species for their susceptibility to the fungus, which originates in South America. The first three tested have shown high sensitivity.
Martino said the rust drove plant species to extinction, so understanding how different plants reacted would help the conservation effort.
Shuey said it would be critical to keep the rust out of Queensland’s biodiversity hotspot in the southwest, as it was the most diverse area in the world for myrtaceae — home to nearly half of the world’s species.
Bob Makinson, a conservation botanist, coordinated a national action plan — developed voluntarily by concerned scientists and wildlife managers — through the Australian Network for Plant Conservation.
About 350 Australian species have been identified as hosts of fungi. Makinson said the myrtaceae in the state’s southwest were intrinsic parts of the ecosystem.
“Many of them are part of the spring wildflower communities that attract tourists from all over Australia and the world,” he said.
“If it settles there, we’re likely to see a big increase in the number of host species and in the number of native species that are threatened with decline or extinction. That could be a biological disaster.”
The fungus especially likes moisture and fresh vegetation, so it thrives in new growth after rain or after forest fires, meaning the wet conditions in the east of the country would have provided the perfect environment.
The National Action Plan was finalized in 2020 but has not yet been formally approved by governments.
“While some agencies and researchers are acting heroically, their efforts need to be broadened, merged and better funded,” Makinson said.
James Trezise, conservation director at the Invasive Species Council, said myrtle rust caused a “silent extinction” among Australia’s diverse plant life.
“Clearly, the system for dealing with this major environmental threat is not working,” he said.
“Australia already holds the inglorious title as the world leader in mammalian extinction. If we don’t strengthen our threat mitigation and biosecurity systems, we could also see ourselves as a global leader in plant extinction.”
Federal Environment Minister Tanya Plibersek agreed that a coordinated response was needed and said the government is working to implement a national action plan.
“Targeted investments have been made to create a national inventory of myrtle rust susceptible species and provide specific myrtle rust training to native forest rangers and landowners in NSW and Queensland,” she said.