BIOSECURITY UPDATE: Polyphagous shot-hole borer detected in Western Australia (November 2021)

Monday, 29 November 2021

Polyphagous Shot-Hole Borer (Euwallacea fornicates) has been detected for the first time in Australia in East Fremantle, Western Australia.

The Western Australia Department of Primary Industries and Regional Development (DPIRD) are responding to the detection of this exotic beetle, and further surveillance in the East Fremantle and Fremantle areas are underway to determine its spread.

DPRID initially established a quarantine zone around East Fremantle and Fremantle to prevent further spread of the pest, and to allow for urgent ongoing surveillance activities.

On 16 November 2021, an expanded quarantine area came into effect covering 17 WA local government areas, as 21 infested properties have been confirmed.

To date, DPIRD have collected positive samples from 6 different species of trees including: Box elder maple, Coral tree, Sophora, Poinciana, Mango, and Sugar maple.

A fungus was also found with the borer and testing has determined it is a Fusarium species which is closely related to Fusarium variasi. More detailed testing is being conducted by Royal Botanic Gardens in Sydney to determine if it’s an exotic species.

This exotic beetle poses a significant threat to production nurseries, fruit, and nut trees, and the forestry industry if it spreads. Already established in South Africa, this pest has caused significant economic impacts from the removal and treatment of dead trees.

About the Polyphagous Shot-Hole Borer

The adult female beetles are 2mm long and tunnel into tree stems and branches. Updated information indicates the borer tunnels into the tree’s stems and branches, causing damage and dieback, from as small as 20mm in diameter up to large trucks and branches – a change from the initial 10mm branch diameter guideline.

This beetle spreads with the movement of infested trees, firewood, and green waste material. After mating, female borers then disperse to look for suitable host trees and may fly up to 400 metres.

This pest has a symbiotic relationship with the fungus Fusarium euwallaceae, which is used as a food source for the beetle and its larvae. Fungus samples were found with the borer in Western Australia, and testing is currently underway to confirm if it is the symbiotic fungus, Fusarium euwallaceae. This fungus disrupts water and nutrient movement within the vascular system of susceptible trees, causing the disease Fusarium dieback which causes are wilting and dieback of tree branches and leaves, often starting in the upper canopy.

The adult beetles and their larvae can be hard to spot as they spend most of their lives inside a tree; however, there are several symptoms that indicate the borer could be present including:

  • Multiple entrance holes, up to 2mm diameter or the size of the tip on a ballpoint pen, on the trunk or branches.
  • Frass (white) extruding from the tree and crystalline foam which look like sugar volcanoes exuding from the entry holes.
  • Thick resin or sap on the tree’s branches or trunk. This can sometimes push the beetle out of the gallery.
  • Dark brown to black staining of the wood around entrance holes.
  • Wilting and dying branches and eventually tree death.

Trees in which the beetle is able to breed and multiply are referred to as reproductive host trees. Reproductive hosts trees include maple, oak, plane, coral tree, avocado and willows. Non-reproductive host trees are attacked by the beetle, but the beetle does not establish galleries, also called tunnels.  The beetle does not breed in these trees. Non-Reproductive host trees include eucalyptus, citrus, jacaranda, figs and olives.

Biosecurity requirements

A Quarantine Area Notice is currently in place to help contain the spread of the borer in Western Australia. This means that containerised plants, trees, mulch and wood cannot be removed from the quarantine area which is applied to parts of Fremantle, East Fremantle, North Fremantle, Palmyra and Bicton for an initial period of six months.

To view the quarantined area, click here for a detailed map.

Residents in East Fremantle have been advised to check their trees for signs of borer damage and wilting and to not remove wood or green waste material from their property unless it is through an approved council collection.

The Consultative Committee on Emergency Plant Pests met in October and November 2021 to discuss this detection. It was recommended that the polyphagous shot-hole borer and the fungus associated with it, are emergency plant pests as defined by the Emergency Plant Pest Response Deed. The committee agreed that more information is needed in terms of its current distribution before they can make a recommendation on the technical feasibility of eradication.

If you detect any signs of borers in host plants, please contact the Exotic Plant Pest Hotline on 1800 084 881 right away – early detection is vital for managing and eradicating pests and disease. Immediate instructions will be given on how to collect and submit samples.

For further information contact National Biosecurity Manager John McDonald via email at john.mcdonald@greenlifeindustry.com.au.

The ‘National biosecurity and sustainable plant production program’ (NY20001) project is funded by Hort Innovation using nursery research and development levy and funds from the Australian Government.