An invasive fungus attacking some of Australia’s most ecologically important tree species has spread to Western Australia while also thriving in wet conditions across the east of the country, causing a “silent extinction” and prompting so-called urgent for a national response.
Experts warn that if the myrtle rust fungus detected in the eastern Kimberley reaches the biodiversity-rich southwest of the state, the consequences could be disastrous for those ecosystems.
Since it was detected in a New South Wales nursery in 2010, the fungus, recognizable by its bright yellow spots and rust on leaves, has become established along the eastern seaboard and has been detected in every state except in South Australia.
A 2021 study predicted that myrtle rust could claim at least 16 rainforest plants within a generation in an extinction event of “unprecedented magnitude”.
The fungus affects plants in the myrtaceae family, a diverse group that includes rainforest species, paperbark, eucalyptus and myrtle. The native guava, once widespread, has been nearly wiped out by the fungus.
A team led by the WA Department of Primary Industries detected the fungus in nine broadleaf and narrowleaf paperbark in the eastern Kimberley in late June. The exact species of melaleuca affected is not yet known.
The department is inspecting tourist hotspots and nurseries, with no new detections so far. Potential impacts “have yet to be determined,” a department spokesman said, but the disease could cause tree death, dieback, species loss and compromise ecosystems.
Dr. Louise Shuey, a forest pathologist with the Queensland Department of Agriculture and Fisheries, traveled to the Kimberley to help with the screening effort.
“Myrtle rust can travel hundreds of kilometers in the wind and that is why it is spreading so widely,” he said.
The location was sought after the model pointed to an isolated wetland as a likely location, stretching from the affected plants in the Northern Territory to the east.
Alyssa Martino, a research scientist at the University of Sydney, has started testing 25 species of WA melaleuca for their susceptibility to the fungus, which originated in South America. The first three tested have shown high susceptibility.
Martino said the rust was driving plant species to extinction, so understanding how different plants reacted would help the conservation effort.
Shuey said keeping the rust out of Queensland’s biodiversity hotspot in the southwest would be crucial, as it was the most diverse area on the planet for myrtaceae, with almost half of the world’s species.
Bob Makinson, a conservation botanist, coordinated a national action plan, developed voluntarily by concerned scientists and wild plant managers, through the Australian Network for Plant Conservation.
About 350 Australian species have been identified as fungal hosts. Makinson said myrtaceae in the southwestern part of the state 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 becomes established there, we are likely to see a huge increase in the number of host species and the number of native species threatened with decline or extinction. That could be a biological disaster.”
The fungus especially likes moisture and cool vegetation, so it thrives on new growth after rain or after a forest fire, meaning the humid conditions in the east of the country provided the perfect environment.
The national action plan was finalized in 2020, but has not been formally adopted by governments.
“While some agencies and investigators are heroically active in this, their efforts need to be expanded, united and better resourced,” Makinson said.
James Trezise, director of conservation for the Invasive Species Council, said myrtle rust was causing a “silent extinction” among Australia’s diverse plant life.
“It is clear that the system to deal with this huge environmental threat is not working,” he said.
“Australia already holds the ignominious title of world leader in mammal extinction. If we don’t strengthen our biosecurity and threat reduction systems, we may also find ourselves world leaders in plant extinctions.”
Federal Environment Minister Tanya Plibersek agreed a coordinated response was needed and said the government was working to implement a national action plan.
“There have been specific investments to do a national inventory of myrtle rust susceptible species and to provide specific myrtle rust training to indigenous rangers and landowners in New South Wales and Queensland,” he said.