Threats

Polyphagous Shot Hole Borer

An invasive beetle is moving toward Perry Lakes. Here’s what to look for — and what to do if you find it.

Photo: Ian Stewart

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The threat

What is PSHB?

The polyphagous shot-hole borer (Euwallacea fornicatus) is a beetle native to Southeast Asia, roughly the size of a sesame seed. It tunnels into the trunks, stems and branches of a wide range of trees and farms a fungus (Fusarium euwallaceae) inside the tunnels as a food source for itself and its larvae.
The fungus blocks the flow of water and nutrients inside the tree, causing dieback and eventually tree death. There is currently no registered spray or chemical to combat either the insect or the fungus in Australia.

The beetle itself — about the size of a sesame seed. Image courtesy of DPIRD.

Bore holes in trunks or branches, approximately 1 mm in diameter. Image courtesy of DPIRD.

Identification

Six signs of infestation

The beetles themselves are tiny — the size of a sesame seed. In practice, you’re looking for the damage they leave behind. Check tree trunks and fallen branches.

Small circular holes

Approximately 1 mm in diameter, perfectly circular, in the trunk or branches.

Discolouration or staining

Staining or discolouration of the tree trunk or branches around the holes.

Gumming

Resin or sap exuding from the holes — sometimes pushing the beetle out.

Dieback

Death of the uppermost branches. Can also be caused by other factors, including Phytophthora dieback.

Galleries inside the branch

Networks of tunnels (galleries) visible inside the tree branch when it is broken open.

Sawdust or frass

Fine sawdust or frass exuded from the holes and collecting on bark or at the base.

Proximity

PSHB at Perry Lakes

It’s only a matter of time

PSHB has been confirmed in suburbs surrounding Perry Lakes on all sides — to the west at Lake Claremont, to the south at Masons Gardens in Dalkeith, to the north at Wembley Golf Course, and to the east in Floreat, Wembley and West Leederville. The beetle was first identified in North Fremantle in September 2021.

400 m

the maximum flight distance of a female PSHB beetle — far enough to bridge the gap from surrounding infestations.

N ↑

Perry
Lakes

Wembley Golf CourseNorth

Floreat · WembleyEast

Masons GardensSouth · Dalkeith

Lake ClaremontWest

Confirmed infestation

Schematic — confirmed infestations recorded to March 2024. Not to scale.

Risk profile

Host trees at Perry Lakes

Whether a tree is infested depends on its susceptibility and the intensity of attack. Reproductive hosts produce new female beetles and carry the highest risk.

Reproductive hosts — highest risk

Can produce female beetles that infest other trees

Casuarina obesaSwamp sheoak	Reproductive host — produces female beetles
Corymbia calophyllaMarri	Reproductive host — also occurs in Bold Park
Melaleuca rhaphiophyllaSwamp paperbark	Reproductive host
Platanus × acerifoliaLondon plane tree	High-risk preferred host on the Underwood Avenue verge (outside reserve)
Ficus macrophyllaMoreton Bay fig	Single tree west of West Lake — high-risk preferred host

Non-reproductive hosts — lower risk

Can be infested, but breeding galleries are not established

Agonis flexuosaWillow myrtle / peppermint	Can be infested but breeding galleries not established
Eucalyptus gomphocephalaTuart	Can be infested — not expected to die
Eucalyptus rudisFlooded gum	Main canopy tree in reserve — canopy loss would be significant
Acacia salignaOrange / yellow wattle	Can be infested — not expected to die

Our response

What FoPL is doing

Friends of Perry Lakes is working with the Town of Cambridge to raise awareness of PSHB risk and recruit citizen scientists to inspect and report potential infestations.

Members and visitors are encouraged to inspect tree trunks and fallen branches during visits to the reserve — binoculars can be useful for checking higher branches. Early management of preferred host trees, especially, will lessen the risk of infestation spreading through the reserve.

You can help

Download the MyPestGuide Reporter app and report any signs of PSHB you find at or near Perry Lakes. Every report helps DPIRD track the beetle’s spread.

Download MyPestGuide Reporter →

References