Polyphagous shot-hole borer (PSHB), a wood-boring exotic beetle which has been gradually spreading across the Perth metropolitan area since August 2021, was first detected in the City of Subiaco in January 2023, and has spread to further City locations.
Trees at Subiaco Common, Lake Jualbup, and Rosalie Park are among those affected.
The City anticipates a general increase to PSHB spread rate, and an increase in secondary infections in line with global trends, as pest numbers increase and tree health declines due to persistent pest pressure.
The City is working closely with the Department of Primary Industries and Regional Development (DPIRD) to monitor the situation. Where trees are infected, DPIRD will be implementing prescribed treatments, which can include pruning of the tree or its full removal.
In the event that a tree has to be removed, the City will endeavour to replace with a native tree species as soon as is reasonably practicable.
Mayor David McMullen said, “The City has a robust tree inspection program to promote tree health, and we are actively monitoring the spread of PSHB across our suburbs.
“We cannot accurately predict how many more trees will be infected, and acknowledge this is an ongoing problem for so many places around the world.
“The City is proactively trying to limit the spread, taking advice on recommended measures from DPIRD. But the successful management of PSHB remains a new challenge that not only City of Subiaco - but also others presented with the PSHB problem - are still working out how to best manage.
“For now, we’d encourage our residents to help monitor for PSHB, as early detection is key to minimising further impact on neighbouring trees.”
There are a number of symptoms that indicate a tree may be infested, including:
- Beetle entry holes (approximately the size of a ballpoint pen tip)
- Discolouration or staining of wood
- ‘Gumming’; the appearance of thick resin or sap
- ‘Galleries’; intricate tunnels or galleries where PSHB farm fungus
- Frass; a noodling effect that can be present extruding from trees, produced by the beetle’s tunnelling
- Dieback.
Important trees to check are maple, willow, plane, coral tree and avocado.
Residents who suspect they have borer damage to trees should call the DPIRD’s Pest and Disease Information Service on 9368 3080 or email padis@dpird.wa.gov.au. Further information can be found at www.agric.wa.gov.au/borer