Council warns Aussies to check gardens amid threat of 'highly invasive' pest

Trees affected by the destructive insect can 'quickly become public safety hazards' and pose a huge threat to Australia's native environment.

Brianne Tolj
·Associate News Editor
Updated ·4-min read
Polyphagous shot-hole borers on a tree branch.
A Perth council is urging residents to inspect their gardens for the 'highly invasive' polyphagous shot-hole borer. Source: City of Canning/Facebook

A concerned council is urging residents to inspect their gardens for a new “highly-invasive” pest that is causing chaos in one of Australia’s biggest cities.

Native to Southeast Asia, the polyphagous shot-hole borer was first found in Fremantle, WA, in 2021 — confusing experts on how it got into the country and sparking fears the destructive beetles could wipe out forests and agricultural crops. The issue has since escalated rapidly, leading to the creation of a quarantine area which was expanded in September to encompass Perth’s entire metropolitan area.

This week, the City of Canning — an area deemed to have high numbers of infested trees — asked locals to do their own part to help tackle the pest that works symbiotically with fungus to block a tree’s water and nutrients, killing it within two years.

“Be alert for the polyphagus shot-hole borer (PSHB) in trees near you,” the council posted on Facebook, listing a handful of the hundreds of tree species it has been known to attack.

Left, the small holes polyphagous shot-hole borers make in tree branches. Right, close up of a burrowed polyphagous shot-hole borer.
If Perth locals discover tiny holes in their tree branches, they are urged to report the suspected infestation to authorities. Source: DPIRD

“PSHB causes serious damage to many types of trees, but it particularly loves to hide in the box elder maple (Acer negundo). We are asking people who have a box elder maple on their property or street to report the location of these trees, so we can check if they are infested with PSHB.”

Locals should all keep a close eye on any of the below:

  • Black Locust (Robinia)

  • Coral tree (Erythrina)

  • Plane tree (Platanus)

  • Fig (Ficus)

  • Poinciana (Delonix)

  • Mulberry (Morus)

  • Willow (Salix)

If anyone discovers tiny holes the size of a ball point pen in clusters, they are urged to report the suspected infestation to the Department of Primary Industries and Regional Development (DPIRD).

Affected trees can “quickly become public safety hazards and a constant source of beetles that can disperse to neighbouring trees, causing spread,” the department’s website says.

There are 30 local government areas now included in the state’s PSHB quarantine area, which divides Perth into two zones, each with different rules that residents must follow.

Zone A includes suburbs with high numbers of the beetles where intensive control activities such as tree removal are currently underway. Those living in the designated area face heavy restrictions on the movement of plants, gardening equipment and wood out of that zone.

Left, the polyphagous shot-hole borer quarantine zone in WA. Right, a tree susceptible to polyphagous shot-hole borer.
The state's PSHB quarantine area was expanded in September after the beetles appeared in four additional suburbs. Source: DPIRD

Zone B is a buffer zone around towns with few or no infested trees, and while residents face the same restrictions, they can move wood and living plants back into Zone A.

A few months ago the beetle was found to have beached the previous quarantine zone, popping up in four separate suburbs and confirming concerns the pest is spreading despite the DPIRD’s $41 million response plan.

Margaret Thomas, the mayor of Kalamunda where the beetle was recently detected, said the discovery had made locals “very nervous”. “Kalamunda is very protective of our forests and to know it’s that close to the forest is very concerning,” she told ABC Radio Perth in August.

  • Use grass clippings or compost as mulch where possible in your garden as wood chips from non-reputable places can spread PSHB.

  • While pruning or gardening check your plants and branches for signs of the borer.

  • Disinfect pruning tools. Any tools that come into contact with infected wood should be sanitised before using on uninfected trees.

  • Try to avoid moving plants or wood products too far from your local area inside the Quarantine Area.

  • Don’t move plants, wood or green waste from a known beetle infestation area.

  • Follow the current Quarantine Area requirements.

  • Plant native species over exotic plants.

  • Don’t take it upon yourself to dispose of a possibly infested plant.

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