Biosecurity Alert Update #2 - Euwallacea fornicates Polyphagous shot-hole borer

Situation

The Western Australia Department of Primary Industries and Regional Development (DPIRD) is responding to the detection of an exotic beetle, Polyphagous Shot-Hole Borer (Euwallacea fornicatus) in a 30-year-old backyard maple tree in East Fremantle. Polyphagous shot-hole borer is a tiny beetle (about 2 mm in length) that bores into the stems and branches of living trees, as small as 20mm in diameter up to larger trunks and branches, resulting in damage and dieback, ultimately resulting in tree death. It is considered both an agricultural and environmental pest with more than 400 host species including horticulture production, native and amenity trees.

This is the first time that Polyphagous Shot-Hole Borer has been detected in Australia. Further surveillance in the East Fremantle and Fremantle areas by DPIRD has established eight infested properties and four properties with suspected detections awaiting examination. Unfortunately, a further seven infested properties are outside of the existing quarantine zone, initially set up by DPIRD to contain the spread, bringing the total number of infested properties to fifteen.

To date, DPIRD have collected positive samples from six 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. Polyphagous shot-hole borer has a symbiotic relationship with the fungus Fusarium euwallaceae, which is used as a food source for the beetle and its larvae and can cause tree death, however this species has not yet been identified in borers sampled to date in WA. 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. And the beetle does not breed in these trees. Non-reproductive host trees include eucalyptus, citrus, jacaranda, figs and olives.

In South Africa the Polyphagous shot-hole borer is established, and the removal and treatment of dead trees in urban areas has caused significant economic impacts.

Identification information here

All growers are encouraged to report any signs of loopers on host plants to the Exotic Plant Pest Hotline on 1800 084 881. Instructions will be given on how to collect and submit samples for identification. Your cooperation will assist in delimiting the spread of this unwanted new pest species.

For further information email John McDonald, GIA National Biosecurity Manager : john.mcdonald@greenlifeindustry.com.au

Developed by the GIA National Biosecurity & Sustainable Plant Production Program Team 2021