The Department of Primary Industries and Regional Development (DPIRD) is responding to the confirmed detection of an exotic beetle, the Polyphagous Shot-Hole Borer (PSHB) in the Perth metropolitan area.
The first detection was in East Fremantle in August 2021 and detections have been made in suburbs along the Swan-Canning River. Subsequently, PSHB has now been detected in Kings Park.
PSHB (Euwallacea Fornicatus) is a black or brown beetle approximately 2mm in length that is native to Southeast Asia. The beetle attacks a wide range of plants by tunnelling into trunks, stems and branches.
The beetle has a symbiotic relationship with a Fusarium fungus, cultivating it inside the tree as a food source for the beetle and its larvae. In susceptible trees, the fungus kills vascular tissue causing Fusarium dieback and tree death.
The establishment of this pest in WA may have a significant impact on urban trees, native trees and certain industries. As this is the first detection in Australia, the full impact of this pest will not be known for some time.
Further information and map of the quarantine area can be found at agric.wa.gov.au/borer.
Impact on Botanic Gardens and Parks Authority (BGPA)
To date, BGPA has not recorded any widespread canopy decline or infestation; no trees have died from PSHB or the associated Fusarium dieback. However, there has been detections in a number of Ficus macrophylla (Moreton Bay Fig), Ficus rubiginosa (Port Jackson Fig) and Erythrina caffra (Coast coral Tree).
BGPA is coordinating an internal response to manage the current site, to better understand the extent of the incursion, and to limit spread of PSHB on BGPA property. This involves a coordinated response by BGPA staff and volunteers, and working closely with our colleagues at DPIRD, DBCA and other key stakeholders.
BGPA is working closely with DPIRD to manage trees damaged by PSHB. The pruning or in some cases removal of infested trees is key to containing PSHB spread and minimising further impact on neighbouring trees.
An extensive and ongoing survey of target trees will be undertaken to monitor trees damaged by PSHB and to identify any additional sites on BGPA lands. BGPA staff and volunteers have been trained in the spotting of potential incursions and they will also be on the lookout in Bold Park.
Impacted species currently are Ficus, Erythrina, Platanus or Quercus however, there is potential for PSHB to infect some native species. Control agents and methods for protecting our collection and treating infested sites are being actively investigated.
To date, DPIRD has inspected more than one million trees across Perth, these inspections have detected PSHB in only three species native to WA. This includes Cockie’s tongue (Templetonia retusa) and Wedding bush (Ricniocaprus tuberculatus x cyanescens) both hosts are single records and do not appear to be preferred PSHB hosts in WA.
Of the thousands of red flowering gum (Corymbia ficifolia) trees inspected, PSHB has been detected in only two trees in Perth. Whilst red flowering gum has been confirmed as a host, they appear to be infested under specific circumstances such as stress.
DPIRD is currently determining the local host range as PSHB may behave differently in Western Australia. This host list is regularly updated and available from agric.wa.gov.au/borer.
It is critical that no plant material be removed from BGPA lands or transported between Bold Park and Kings Park to prevent inadvertent spread of PSHB.
Members of the public can assist with the control of PSHB by looking for the signs of an infestation in trees in the park, in home gardens and around your local area. These signs include entry holes the size of a ballpoint pen tip, discolouration of wood, and gum or frass being extruded from the tree.