Polyphagous
shot hole borer (PSHB)

About

The polyphagous shot hole borer (PSHB, Euwallacea fornicatus) is a tiny, invasive wood‑boring beetle native to Southeast Asia. It poses a serious threat to horticultural, environmental, and amenity trees by attacking a wide range of species. So far, there are over 400 globally documented hosts, including Australian natives.

Female beetles (~2 mm long) bore into the trunks and branches of living trees, creating galleries deep in the wood. They have a symbiotic relationship with the Fusarium fungus, which they cultivate inside these tunnels. This disrupts vascular tissue and impedes water and nutrient flow, leading to dieback, branch failure and eventual tree death. Only females fly – males are wingless and remain inside the tunnels.

PSHB was first detected in August 2021 in East Fremantle and remains confined to the Perth metropolitan quarantine area. Spread occurs through movement of infested live plants, firewood, wood chips, mulch, prunings and timber.

Detection and symptoms include clusters of tiny (~1 mm) round 'shot holes' in bark or branches, often surrounded by frass, gumming or staining. Leaves may wilt and die back, usually starting from the upper branches.

Control methods

Do not attempt to control a suspected PSHB infestation yourself before referring directly to advice from DPIRD. The information on this page is intended as a guide only.

Pruning or removing infested trees or branches

• Follow DPIRD guidance (see their online training) on how and when to prune or remove infested wood.

• Do not attempt chemical treatments. None have been proven effective, as systemic insecticides can't reach the beetle inside galleries, and surface applications are ineffective.

• Do not burn infested wood. Burning the wood encourages the beetles to spread.

Green waste

• Any machinery used for handling infested wood must be cleaned before leaving the area.

• If organising disposal, use licensed DPIRD‑approved green‑waste facilities which will ensure the wood is chipped thoroughly—two passes through grinders—to kill pests before disposal.

• Avoid composting or mulching with freshly chipped wood at home. If mulching, use only dry material or composted, non‑wood sources like lawn clippings.

Host tree planting & prevention

• Reduce high-risk trees on your property: consider replacing highly susceptible species (reproductive hosts) with less‐favoured or native alternatives (non-reproductive hosts, or species with negligible susceptibility).  DPIRD is maintaining a list of affected plants here. Note that some native species are very susceptible.

• Clean and disinfect pruning tools and equipment after working with green waste or suspect trees to prevent unintentional spread.

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