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Biosecurity experts have warned a tiny beetle wreaking havoc in suburban Perth could make its way across the country and devastate Australia’s east coast.
The polyphagous shot-hole borer has been spreading through metropolitan Perth for the past four years, with local authorities at their wits’ end on how to deal with it.
The invasive beetles bore tunnels through tree trunks, causing a fungus to grow inside, which they then feed on.
The fungus needs water and nutrients to grow, and it disrupts the tree’s circulatory system, effectively cutting off its access to water and nutrients, causing it to die.
Local authorities have chopped down infected plants and hundreds of trees in an attempt to stop the spread – however, the efforts have been futile.
The invasive wood-boring beetle, about the size of a sesame seed, was first detected in August 2021 in the port city of Fremantle, 20km south of the Perth CBD.
Western Australian Agriculture Minister Jackie Jarvis revealed last week that the state had given up the fight to eradicate the pest.
The state government has decided to focus on trying to slow the spread after a National Management Group meeting last Wednesday determined it was no longer feasible to eradicate the shot-hole borer from WA.
The decision came after considering the latest scientific data and advice from the country’s chief plant health managers and leading plant biosecurity experts.
A new national management plan is now being finalised.
Since the destructive pest was detected, it has infested thousands of trees, many in iconic Perth parks including Kings Park.
Ms Jarvis said protecting Perth’s tree canopy and the valuable horticulture sector remained front and centre for WA as the national biosecurity response moved into a management phase.
‘We will continue to look for alternative solutions by supporting local scientists to undertake more research under WA conditions,’ she said.
Exactly how the beetle arrived from its native South East Asia remains a mystery, but it has already established infestations in California, Florida, Texas, South Africa, Israel, Sri Lanka, Vietnam, India, Mexico and Thailand.
Despite its global devastation and widespread scientific research, a cure remains elusive.
Part of the problem is the beetles are tiny (2–4mm), and their hidden, tunnel-based life makes them hard to treat chemically.
The fact that it attacks nearly 700 known tree species including avocadoes, maples, willows, native gum trees and oaks, further complicates tracking and containment.
Trials of plastic wraps have largely failed, with the only current intervention being to cut down and chip infected trees.
The Invasive Species Council has warned the decision to end efforts to eradicate the polyphagous shot-hole borer in WA could put the rest of the country at risk.
Council policy director Carol Booth said if the beetle made it east, Sydney’s lush urban canopy, already under pressure from development, could face mass dieback, hotter streets and the loss of habitat for fauna.
‘This is tragic news not just for Western Australia, but potentially for native trees, towns and cities, and the horticultural industry across the entire country,’ she said.
‘Fifteen native tree species in WA have already been identified as highly or very highly susceptible to the polyphagous shot-hole borer, including iconic species like figs, paperbarks, banksias and eucalypts.
‘Another 23 species are moderately susceptible, and that’s just in the Perth region. It implies hundreds of native species across the country could be at risk if the borer spreads.’
Ms Booth said there were grave concerns about the loss of urban trees, which provide vital habitat, shade, beauty and health benefits in cities and towns.
‘The environmental and social toll could be immense,’ she said.
‘We need to learn from this failure. An independent, transparent review is needed to assess whether more could have been done sooner, whether there were delays, missed early detection opportunities, or gaps in public support.
‘This beetle was one of Australia’s top biosecurity prevention targets. The regular arrival of harmful new invaders shows our prevention systems are not strong enough.’
Australia’s forest industries are disappointed that the Commonwealth and state governments have given up trying to eradicate the insidious pest
Australian Forest Products Association chief executive Diana Hallam said the likelihood of it spreading from metropolitan Perth to other parts of the country had increased as a consequence of the decision to move from an eradication to a management strategy.
‘The risk this beetle poses to trees in forestry operations, national parks, reserves and even backyards is immense, and the cost borne by our industry and other stakeholders, like local councils, to prevent its spread and manage its risk will, unfortunately, likely increase,’ she said.
‘We know in South Africa and California, where the borer has already established itself, the losses and cost of management are in the billions of dollars across local governments, horticulture, forestry and the environment through tree deaths or increased management costs.’
