The chief scientist of the Botanic Gardens of Sydney is warning of a significant and deadly threat to the city’s trees, posed by an invasive beetle that has already led to the removal of thousands of trees in Perth. This tiny polyphagous shot-hole borer, native to south-east Asia, is a “fungus farmer” that burrows into trees, allowing a fungus to colonize and kill them.
Detected for the first time in a Perth tree in 2021, the beetle had spread to more than 200 locations across Perth by the following year, resulting in the removal of approximately 4,000 trees, including Moreton Bay and Port Jackson figs, in an attempt to eradicate the beetle. However, it has been determined that eradication is no longer feasible, and efforts will shift towards managing the invasive pest.
Brett Summerell, the chief scientist at the Royal Botanic Garden in Sydney, expresses concern about the potential impact of the beetle in eastern Australia, particularly in formal gardens. He warns that with a shift in focus from eradication to management, the beetle is likely to spread further, and there is a significant risk of it being transported to Sydney via infested wood, such as firewood.
While there are known host trees in Sydney, such as plane and fig trees, the exact number of tree species susceptible to the beetle is unknown, leading some to refer to the situation as a “big experiment”. This poses a significant risk to the heritage values and appearance of popular parks and gardens, as well as the natural urban cooling provided by these trees.
Carol Booth, the policy director at the Invasive Species Council, emphasizes the need for funding research to investigate additional control options and collaborate with overseas researchers. The council also seeks more research on the potential impacts of the shot-hole borer on native species and their overall environmental impact.
Public awareness and reporting of potential infestations are crucial in monitoring the presence of the beetle. Signs of an infestation include tiny entry and exit holes in the tree’s bark and wilting and dieback of branches.
Source: https://www.theguardian.com/environment/2025/jul/08/polyphagous-shot-hole-borer-invasive-beetle-wa-perth-sydney-nsw-warning
