Authorities place entire city under quarantine after concerning discovery: 'Could put the rest of the country at risk'

Perth is entering a new phase of a battle it never wanted to fight: protecting its tree canopy from a beetle no bigger than a sesame seed. After years of rapid spread and thousands of dead trees, officials are shifting from trying to wipe out the polyphagous shot-hole borer to figuring out how to live with it, 7News reported.

What's happening?

Western Australia has redrawn its quarantine map for the entire Perth metropolitan area, marking a major shift from the state's earlier, more aggressive attempts to eliminate the polyphagous shot-hole borer. The insect, first found in Fremantle in 2021, has carved through thousands of trees and forced removals in Hyde Park and Kings Park. With no effective chemical treatments and persistent challenges identifying early infestations, the state formally ended its push for eradication in June.

It was a pivot that alarmed experts. The Invasive Species Council warned the decision "could put the rest of the country at risk."

Under the new plan, Perth is now split into two zones: an inner management zone where the borer is firmly established and an outer containment zone where officials hope to stop it from spreading further. The Department of Primary Industries and Regional Development will prioritize pruning and removals in the containment area to keep the beetle from reaching regional communities and agricultural corridors. 

Why is the borer's spread concerning?

Invasive species disrupt ecosystems by outcompeting native plants and animals and weakening the landscapes they've long supported. Once this beetle tunnels into a tree, it introduces a fungus that blocks the transport of water and nutrients, slowly starving the tree until it dies. Losing canopy cover affects everything from neighborhood heat levels to wildlife habitat to food-growing conditions.

"Early detection and management of high-risk infestations, particularly in the containment zone, remain critical to managing the spread and impact," DPIRD's Mia Carbon told 7News. 

Since native species often have no natural defenses against invaders, delays can give pests a massive advantage. That imbalance threatens biodiversity as well as soil and water health, and it increases the risk of future pest-borne diseases.

What's being done about the borer?

DPIRD is working directly with affected property owners, giving them the option of pruning or removing for free trees that were selected during the eradication phase. They may also choose to manage their trees independently with department guidance. The state has committed 4.7 million Australian dollars to local governments in impacted areas and for research into treatment options. 

Residents can support containment by reporting suspicious tree damage, avoiding moving untreated wood, and choosing native plants to strengthen local ecosystems.

"By working together, we will have the best chance of limiting the spread of the borer and minimising its impact on our tree canopy and valuable horticulture industries," Carbon said.

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