DPIRD Polyphagous shot-hole borer update

Polyphagous shot-hole borer: prevention and management

This article was prepared by the Department of Primary Industries and Regional Development DPIRD) WA.

Where PSHB came from and where it is now

Native to Southeast Asia, Polyphagous shot-hole borer (PSHB) has spread to several parts of the world, including the United States, South Africa and, since August 2021, Western Australia.

While the pest is currently confined to the Perth metropolitan area, a Quarantine Area remains in place in Western Australia as a key biosecurity measure to reduce the risk of human-assisted spread.

Growers in regional Western Australia and across the country should remain vigilant and understand the risks posed by PSHB.

The invasive beetle tunnels into the wood of host trees and carries with it a symbiotic Fusarium fungus, which it cultivates inside the tree. The growth of the fungus disrupts the tree’s vascular system, inhibiting the flow of water and nutrients. This leads to a range of symptoms in avocado trees, including branch dieback and yield loss. Tree death is uncommon in avocados, with damage typically affecting branches rather than the main trunk.

What is DPIRD doing now

DPIRD is transitioning to a management-focused approach aimed at slowing the spread of PSHB and reducing its impacts where it occurs. While impacts on avocado production in Western Australia have so far been limited, overseas experience has shown that PSHB can cause significant damage to avocado trees and has the potential to adversely affect avocado production if it becomes established in major growing regions.

Simple on-farm biosecurity actions can help protect your orchard

1. Monitor and report – regular monitoring is critical for early detection to protect your orchard from PSHB establishment. Know what to look for and report any suspected infestations to your appropriate state or territory biosecurity agency.
2. Movement control – know what comes onto your property. PSHB can spread through the movement of infested plant material, untreated wood products, and mulch containing pieces of host material greater than 2.5 cm in size.
3. Orchard hygiene – disinfect machinery, equipment and tools between blocks or properties to reduce the risk of spread.

What to look out for

A key indicator of PSHB infestation in avocado trees is the presence of “sugar volcanoes”. These appear as white, crystalline or foamy substances exuding from the beetles’ entry or exit holes. The contrast of sugar volcanoes against the bark of avocado trees makes it one of the easiest symptoms to detect.

Sugar volcanoes may appear as a single large mass covering multiple holes, or as smaller deposits over individual shot-holes. These substances can obscure shot-holes, which may only become visible once the material is removed, or in some cases, when the outer layer of bark has been scraped back.

What effective surveillance looks like

1. Conduct regular visual scans of trees, focusing on trunks and branches, looking for evidence of sugar volcanoes or branch dieback.
2. If a sugar volcano is found, carefully remove the material and if necessary, the outer bark to check for small, perfectly round shot-holes (approximately 1 mm in diameter). Note that PSHB can still be present even if no sugar volcanoes are visible, so inspection should not be limited to cases where one is found.
3. Look for additional signs such as tunnels at limb failures and dark staining caused by the beetles’ associated Fusarium fungus.
4. Inspect wounds, including pruning cuts, as these are common entry points.

PSHB favours warm, moist and humid environments, as these provide ideal conditions for both the beetle and its associated Fusarium fungus to develop and spread.

Avocado growers in tropical and subtropical production regions should remain particularly vigilant and regularly monitor their orchards for signs of PSHB infestation.

Monitoring should be intensified during the warmer months, when beetle activity and dispersal are expected to increase.

Early detection and reporting are critical to slowing the spread of PSHB.

Get in touch

If you suspect an infestation in Western Australia, report it via DPIRD’s MyPestGuide Reporter app or contact the Pest and Disease Information Service at padis@dpird.wa.gov.au or (08) 9368 3080.

Outside Western Australia, contact your state or territory biosecurity agency, or report the pest through the Exotic Plant Pest Hotline on 1800 084 881.

This article appears as part of the 27 August 2026 issue of Guacamole, our e-Newsletter.