This invasion poses a significant and ongoing threat to Australia’s tree population. PSHB is an invasive pest, one that is destroying much of the landscape with tragic speed. This little known and rarely noticed beetle tunnels within the branches of over 100 species of hardwood trees. It has spurred the felling of millions of trees around the world from California to Hawaii to Brazil, Argentina, Israel and South Africa. Things have gotten out of hand — in what may be the worst case in the world — in Western Australia. In Perth, the borer has already infested well over 4,900 trees.
The Polyphagous Shot Hole Borer is a formidable pest, boring holes into trees’ branches and cultivating a destructive fungus. The fungus impedes water flow, slowly killing the infested trees. Pyrus calleryana plantings have become hard-hit by widespread infection by this fungus. Furthermore, significant natives including the marri and red flowering gum have recently been re-categorized as high-risk targets for this destructive invader.
Impact on Western Australia
In 2021, Perth experienced the most extreme reaction to a PSHB outbreak, with authorities felling over 5,000 infected trees. The decision highlights the destructive effect the borer has had on the city’s tree canopy. This phenomenon is most evident in major urban parks such as Kings Park. The damage in the park has been drastic, with entire forests in the park exhibiting obvious signs of the infestation’s destruction.
In a landmark resolution of commitment, authorities denied removal of 42 mature Moreton Bay figs and coral trees from a riverside embankment. What’s more, this site had turned into an immensely popular wedding venue. This removal highlights the extensive environmental and social harms that the PSHB has caused. The shattering of these picturesque trees destroys this area’s beauty. It’s bad for our native biodiversity. It harms local ecosystems that rely on these native species.
“That’s a really big number and the scary thing about that number is that it’s doubling every six years.” – Professor Ben Phillips
Both the overall infection rate as well as the quick increase foreshadow a crisis in Australia’s biodiversity.
Research and Government Response
At least the Western Australian government understands how out of control the problem has become. In recent weeks, they have committed more than $2 million to fund university research to develop a strategic framework to combat the PSHB threat. This funding is imperative to furthering research and deploying effective management strategies to combat the borer.
Ben Phillips
Professor of integrative biology
Invasive species management
He has been a vocal critic of the state’s PSHB strategy. He acknowledged the difficulty that Western Australia will have in eradicating such a pest. Challenges related to data sharing between government agencies and a lack of investment or commitment to external research projects pose challenges. He noted that “you need to be able to lubricate the flow of data in between organisations” to effectively tackle such invasive threats.
The future research will go even further, testing both chemical and biological controls against the PSHB. Today, the only effective treatment option is injecting a toxic combination of fungicides and pesticides directly into the trunks of infected trees. Experts warn, as beneficial as these early actions can be in containing outbreaks, they’re not without their vulnerabilities.
“We simply don’t have the resources to manage shot-hole borer along with all of the other invasive pests that we’re already managing.” – Bruce Webber
This quote sums up the bigger picture problem environmental agencies across Australia are faced with as they try to tackle several invasive species at once.
Future Outlook and Predictions
What would happen without the intervention Experts estimate that, if unchallenged, the Polyphagous Shot Hole Borer would reach Australia’s Nullarbor plain and eventually enter Asia. CERIS Bruce Webber, an invasive species specialist, lived in fear of this pest expanding its range. Invasive pests such as the PSHB represent an existential threat to our agricultural and forestry sectors. It is estimated that they cost the Australian economy upwards of $40 billion annually.
“Polyphagous shot-hole borer is just one of many invasive species that are out there and will turn up in Australia at some point and many of those species are going to be more damaging.” – Professor Ben Phillips
This honest statement illustrates the enormous challenge Australia faces in combating invasive species and serves as Canberra’s wake-up call.
To encourage joined-up action to address this growing problem, researchers offered to provide free support to local councils. John Szymanski noted that research teams are willing to treat infected trees if councils can provide vital data regarding tree health and location. “Everyone was enlivened and excited by the fact that this could actually work, so that was the start,” he added.
“We have this great biosecurity system but it’s stretched really thin. The threats are increasing faster than the system is able to cope with it.” – John Szymanski
This call for action highlights the pressing need for enhanced cooperation among various stakeholders in order to effectively manage and mitigate the effects of invasive species like the Polyphagous Shot Hole Borer.
