biosecurity WA CITRUS

The transition of the polyphagous shot-hole borer (PSHB) from an eradication program to long term management marks a significant shift for Western Australia’s horticultural sector.

Words Helen Newman, Citrus Biosecurity Officer, WA Citrus

UNDER the new conditions a Quarantine Area has been established, and movement restrictions apply to high risk materials including firewood, green waste, untreated timber, and live plants that are greater than 2cm in diameter. These measures are essential to safeguarding horticultural regions and regional communities. The Quarantine Area is now divided into two operational zones. The Management Zone, covering the inner metropolitan region, focuses on strategies to live with the pest. Surrounding this is the Containment Zone, stretching from the edge of the Management Zone to the outer boundary of the Quarantine Area.

While citrus is not considered a highly susceptible host, the risk is not zero. Two species — Citrus × latifolia (Tahitian lime) and C. × aurantium (bitter orange) — have shown moderate susceptibility. If PSHB is detected on a citrus property outside the Quarantine Area, growers are required to notify DPIRD. The department will determine the most appropriate response, which may include pruning, tree removal, or targeted chemical control.

Although commercial citrus orchards are at low direct risk, growers should stay alert to what other tree species are planted nearby. Landscape species highly attractive to PSHB — notably Ficus species and coral trees (Erythrina × sykesii) — can become infested and function as reservoirs for the pest. If unmanaged, these infested hosts may allow insect populations to spill into neighbouring orchards.

For growers planning to plant new windbreaks or shelterbelts, consulting DPIRD’s susceptible host list is an important first step to avoid inadvertently introducing attractive species.

Citrus × latifolia and C. × aurantium have shown moderate susceptibility to PSHB.

Exit holes in a tree created by polyphagous shot-hole borer (L); Polyphagous shot-hole borer in a maple tree (R).

Lateral and dorsal views of Euwallacea fornicatus, CC BY 4.0.

Regular inspection and, where feasible, replacement of reproductive hosts in and around orchard boundaries is also recommended to reduce localised risk.

Staying informed and proactive will be key to protecting Western Australia’s citrus industry as PSHB management continues to evolve. To support growers, DPIRD is developing new training and information packages that outline how to reduce spread, protect properties, and identify risks early.

“Even though citrus is at low risk, unmanaged host trees nearby can allow PSHB populations to spill into orchards.”

Polyphagous shot-hole borer | Department of Primary Industries and Regional Development

This includes Frequently Asked Questions, an interactive map of the Quarantine Area, more detail on the movement restrictions.

DPIRD workshops in-person and on-line through February and March.

Contact Helen Newman, biosecurity@wacitrus.com.au or Bronwyn Walsh at industrymanager@wacitrus.com.au or 0400 873 875.