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The Guardian
08-07-2025
- Science
- The Guardian
Invasive shot-hole borer from WA could wreak havoc on Sydney's heritage trees
The chief scientist of the Botanic Gardens of Sydney is warning of an imminent and deadly risk to the city's trees posed by an invasive beetle that has led to the removal of thousands of trees in Perth. The tiny polyphagous shot-hole borer, which is native to south-east Asia, is a 'fungus farmer' that burrows into trees and can spread a fungus that kills the host tree. The larvae of the beetle feed on the fungus, which then colonises the tree's water and nutrient conducting vessels and blocks them, causing stress and dieback that can eventually lead to the tree's death. The beetle was first detected in a tree in Perth in 2021 and a year later had spread to more than 200 locations across the West Australian capital. About 4,000 trees, including Moreton Bay and Port Jackson figs – which are not native to WA – have been cut down during attempts to eradicate the beetle. The beetle can't establish the fungus in all tree species, and it is not known how many types of trees in Australia – native and introduced – could become targets. Overseas, more than 400 host species have been recorded. The West Australian government has its own list of species found to be susceptible. The WA government announced last month that a national management group made up of state, territory and federal representatives had determined it was no longer feasible to try to eradicate the invasive pest and control strategies would shift to managing it. Brett Summerell, the chief scientist at Sydney's botanic garden, said they had been preparing for the beetle to make its way to eastern Australia, where it could have a huge impact in places such as formal gardens. 'We've been concerned for the past couple of years, but that concern is now heightened because the potential for it to be accidentally brought into the Sydney region is quite significant,' he said. Summerell said with the focus shifting from eradication to management in WA, it was 'inevitable' that the beetle would spread further in Perth, and there would be increased opportunities for it to expand – likely via the transportation of infested wood such as firewood. 'I just see the opportunities for people to pick up infested wood and travel east, even all the way to the Sydney region. That risk is going to be heightened because we're moving from eradication to management.' He said because it was not known how many tree species were susceptible, 'it's just a big experiment about to happen'. In Sydney there are large populations of known hosts such as plane and fig trees meaning there was the potential for large numbers to be severely affected, Summerell said. Shot-hole borers could impact the heritage values and appearance of popular parks and gardens – and the amenity trees provide through natural urban cooling. Carol Booth, the policy director at the Invasive Species Council, said it was critical that governments fund research to investigate more control options, including collaboration with overseas researchers. 'One of the highest priorities should be to contain it for as long as possible to give us the time to develop more effective control methods,' she said. The council wants to see more work to investigate the potential impacts of the shot-hole borer in Australia and which native species might be susceptible. 'The big unknown is what is going to be the environmental impact,' she said. 'What the impact is going to be overall in forests. It's really uncertain.' Signs of polyphagous shot-hole borer infestation included tiny entry and exit holes – about the size of the tip of a ballpoint pen – in a tree's bark and wilting and dieback of branches, often starting in the upper canopy. Summerell said monitoring for the presence of the beetle was critical, as was educating the public to identify the signs of a potential infestation, which could start in a backyard tree. 'The more sets of eyes we have looking for potential problems, the more likely we are to find it early,' he said. 'If there are little holes and dots in the trees where it's obvious a borer has been … they should report that.'
ABC News
30-06-2025
- General
- ABC News
South Australia on high alert for shot-hole borer infestations
South Australians have been asked to keep an eye out for an invasive pest that has the potential to wipe out thousands of street and parkland trees, as well as some crops, if it spreads into the state. A national plan is being developed to manage the beetle — the polyphagous shot-hole borer — which was detected in Western Australia in 2021 and has spread through trees in the Perth region. The WA government recently said it would stop trying to eradicate the beetle, which has put authorities in other states on high alert for its presence. South Australian Forest Products Association chief executive Nathan Paine said he was disappointed to see authorities "give up" the fight to eradicate a pest that could cause "untold damage across our urban landscapes and across Australia". "Once a pest is in the country, we need to work as hard as we can, like we have here in SA with fruit fly, to ensure that pest is eradicated," Mr Paine said. He said the state's pine plantations were not under threat, but Tasmanian bluegum plantations, native forests, street trees and botanic gardens were. "If we can stop this now in WA before it becomes significant … we need to make this happen." South Australia's Department of Primary Industries (PIRSA) director of plant and invasive species, Nick Secomb, said the borer had the potential to enter the state from WA in timber, mulch or established trees. He said PIRSA had been monitoring about 500 sites, mainly within metropolitan Adelaide, for signs of the pest. "The real risk for us is that it might get picked and brought here, and so we've had movement controls in place for a while now in our plant quarantine standard," Mr Secomb said. "Luckily we've got that one road in from WA, we've got the Ceduna quarantine station, so all those things get checked." Mr Secomb said PIRSA would work with local councils and nurseries to help identify signs of the shot-hole borer. There is no known treatment beyond removing infected trees and, along with native and ornamental trees, the borer can affect crops including avocados, pears, apples, macadamia and mango. Riverland avocado grower George Loffler said the pest could potentially wipe out SA's avocado industry. "[If it gets here] I don't really see how we're going to stop it, and that's probably one of the scary things," Mr Loffler said. "We don't want pesticides and chemicals affecting our fruit, and it could be a situation where we might have to abandon our harvest if we have to use those options to control the pest. "Where does that leave us as a business and as a family, and where does it leave everyone else along the supply chain that relies on us for avocado supply?" He said the pest was a threat to "every single person out there with a backyard" and everyone had a role in keeping it out of SA. "I guess once they've finished destroying all those, they'll come and eat our avocados."
ABC News
19-06-2025
- General
- ABC News
Invasive beetle puts Australian trees at risk
For the last four years, an invasive beetle has been spreading across Perth, infecting more than 4,000 trees so far. It's known as the polyphagous shot-hole borer and can kill a tree in just two years. Now there's widespread concern from environmental groups that the pest could reach other states, after authorities admitted an eradication plan has failed.
