Polyphagous shot-hole borer: 17 Perth councils under surveillance for tiny beetle that is deadly to trees

Headshot of Jenne Brammer
Jenne BrammerThe West Australian
Polyphagous shot-hole borer
Camera IconPolyphagous shot-hole borer Credit: Supplied by DPIRD Pia Scanlon

A tiny but highly destructive exotic beetle has been detected in Perth trees, prompting the State Government to ban garden waste movements across 17 Perth councils as it determines the extent of the spread.

Residents in the affected area — stretching from Stirling to Cockburn — have been asked to also keep their eyes peeled for signs of the polyphagous shot-hole borer, which can kill a wide range of trees including avocado and citrus, native and amenity trees.

If the borer spreads, it could impact WA’s nursery, fruit and nut tree industries — as well as the forestry industry.

Just 2mm in size, the pest was first detected in East Fremantle in August, after a resident reported signs of dieback and dead branches in their maple tree. Since then, further borers have been detected in Claremont, Myaree, Dalkeith and Attadale.

Polyphagous shot-hole borer
Camera IconPolyphagous shot-hole borer Credit: Supplied by DPIRD Pia Scanlon

Department of Primary Industries and Regional Development chief plant biosecurity officer Sonya Broughton said wood or garden waste must be chipped to pieces that are less than 2.5cm in diameter before leaving the quarantine area.

“This includes bark, potted plants, firewood, tree prunings, logs, plant cuttings, mulch, timber, wood or wood chips,” Dr Broughton said.

Agriculture Minister Alannah MacTiernan said DPIRD was working directly with local governments in the quarantine area to provide information on the borer and on the movement restrictions to help them to support residents.

Map of quarantine zones after detection of Polyphagous shot-hole borer
Camera IconMap of quarantine zones after detection of Polyphagous shot-hole borer Credit: Supplied DPIRD

“Residents can assist by looking for multiple holes approximately the size of a ballpoint pen tip on the trunk or branches, powdered matter extruding from the tree and crystalline foam (sugar volcanoes) exuded from the entry holes,” she said.

Other signs to look out for are thick resin or sap on the tree branches or trunk, dark brown to black staining of the wood around entrance holes, and dying branches and tree death, DPIRD said.

The five most important trees to check are maple, willow, plane, coral tree and avocado.

More than 60 DPIRD officers are involved in managing the threat to WA.

The expanded quarantine area — which came into effect last week after initially being subject to areas around Fremantle — covers local government areas, including Cambridge, Canning, Claremont, Cockburn, Cottesloe, East Fremantle, Fremantle, Melville, Mosman Park, Nedlands, Peppermint Grove, Perth, South Perth, Stirling, Subiaco, Victoria Park and Vincent.

Dr Broughton said as well as the search across Perth, traps have been deployed in Northam, with additional traps to go out to targeted locations in the South West in the coming weeks, to help determine if the borer has spread beyond the metropolitan area.

Any signs of the borer in trees or plant material should be reported immediately to DPIRD.

Get the latest news from thewest.com.au in your inbox.

Sign up for our emails