Polyphagous shot-hole borer

The Polyphagous shot-hole borer is not present in the ACT. The destructive pest is currently established primarily in the Perth metropolitan area of Western Australia.

About the pest

Polyphagous shot-hole borer (PSHB) is a small beetle from southeast Asia. It bores into tree trunks and branches, causing damage that can lead to dieback or even tree death.

PSHB can attack more than 400 types of trees, including Australian native species, fruit trees and many common garden and street trees.

The beetle carries a fungus called Fusarium. The beetle and fungus work together to harm trees. The beetle brings the fungus into the tree, the fungus spreads through the tree’s tissue, and the beetle feeds on it. This combination often causes wilting and dieback, usually starting in the top of the tree.

PSHB was found in East Fremantle, Western Australia (WA) in August 2021. The entry pathway into Australia is unknown, and it has not been detected outside the Perth metropolitan area.

Australia has now moved from tyring to eradicate the pest to long-term management. The WA Department of Primary Industries and Regional Development is leading this work under a national Transition to Management (T2M) plan.

Why they are a problem

PSHB poses a high environmental risk. If it spreads further in Australia, it could significantly reduce urban tree canopy and affect many well-loved tree species.

The adult beetle tunnels into stems and branches, while the Fusarium fungus grows inside the tree. Together they weaken and kill the tree.

What to look for

The adult female beetle is a brown to black beetle, 2 mm long – around the size of a sesame seed. Males are slightly smaller, about 1.6 mm long and wingless. Because the beetle is so small, it is often hard to spot directly. Instead, look for signs such as:

• Small holes in the bark
• Wilting or dying branches
• Sawdust-like material around entry holes
• Dark staining or gumming around the holes.

How it spreads

PSHB spreads mainly through the movement of:

• Infested trees
• Firewood
• Green waste.

The beetle may have arrived in Australia by hitchhiking on untreated wooden packaging or materials.

More information is available on Outbreak - Polyphagous shot-hole borer.

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