A tiny beetle from Southeast Asia is reshaping urban forests in Australia, forcing a costly shift from eradication to long-term management.
The Pest and Its Impact
The polyphagous shot-hole borer (PSHB, Euwallacea fornicatus), first detected in Fremantle, Western Australia, in 2021, does not consume wood directly. Instead, it tunnels into trees and cultivates a symbiotic fungus, Fusarium euwallacea, as a food source. This fungus disrupts the flow of water and nutrients, causing branch dieback and potentially killing the tree.
The insect is capable of reproducing parthenogenetically, allowing a single female to establish a population quickly. Since its discovery, the pest has led to the removal of thousands of trees and prompted a multi-million dollar biosecurity response. In 2025, the Western Australian Government stated that eradication was no longer feasible, shifting focus to long-term management.
- In Perth: Approximately 4,000 trees have been removed. Costs were estimated at A$78 million, with ongoing annual costs of A$9.7 million.
- In South Africa: Estimated costs since 2012 have reached US$16 billion.
Risks to Eastern Cities
A study published in Frontiers in Forests and Global Change assessed the potential risk to urban trees in Sydney, Melbourne, and Brisbane.
Lead author Angus Carnegie estimated that without management, 10–15% of Sydney's trees could die within five years. In a worst-case scenario, 47% of Sydney's urban tree canopy could be killed if all trees at moderate to extreme risk succumbed.
Professor Kingsley Dixon noted that Sydney, Melbourne, and Brisbane face greater risk than Perth due to more favorable humidity and summer moisture, and a higher susceptibility of tree species. At-risk species include Moreton Bay figs, Port Jackson figs, Illawarra flame trees, paperbarks, some eucalyptus species, and imported trees such as oaks and planes. Natural ecosystems are also threatened, including keystone species like she-oaks, broad-leaved paperbarks, and tuckeroo.
Current Management and Surveillance
Under current regulations, it is illegal to move untreated wood, firewood, green waste, mulch, timber, or wood chips out of the Perth Metropolitan Quarantine Area. New South Wales, Queensland, and Victoria have interstate biosecurity controls. Surveillance in these states includes sentinel trees inspected regularly and pheromone trapping.
Scientific Breakthrough: Lab Colony Established
In January 2026, a research team from Murdoch University announced the successful establishment of the first laboratory colony of PSHB in Australia.
This development allows scientists to study the borer's life cycle under controlled conditions.
The team collected beetles from infested locations and recreated their natural environmental conditions in a laboratory setting. The beetles exhibited typical behaviors, including tunneling and supporting the growth of the Fusarium fungus.
Researchers note that a stable colony enables the screening of potential attractants, repellents, and environmentally friendly control methods. The project aims to develop targeted tools based on a deeper understanding of the pest to protect Australia's landscapes from PSHB damage.