Polyphagous shot-hole borer

Polyphagous shot-hole borer (PSHB) is a small exotic beetle that bores into tree trunks, stems and branches, and can lead to tree death.

It was detected in East Fremantle, Western Australia in August 2021.

The beetle is is a high-risk invasive species and an agricultural and environmental pest. It lives in host trees and can be found in over 400 species across amenity, native and horticultural production trees.

To effectively prevent the spread of the beetle, you must follow the import conditions PDF (563.1 KB).

Immediately report suspected infestations and watch out for potential threats.

Image of an adult Polyphagous shot-hole-borer beetle. The beetle is dark brown with a long lower body and large head, with a measurement scale showing it is 2mm long.

Image: An adult PSHB beetle.

Originally thought to be native to Asia, it has been found in many regions, including:

  • Africa
  • South Africa
  • Asia
  • China
  • India (Uttar Pradesh)
  • Israel
  • Japan
  • Malaysia
  • Sri Lanka
  • Taiwan
  • Thailand
  • Vietnam
  • Italy
  • United States (Florida and California)
  • Australia (Western Australia)
  • Samoa
  • Argentina.

As the beetle infestation spreads, it is likely to be found outside of these areas.

Image shows the life cycle of a PSHB beetle, from an egg to larvae to pupa to adult female and male forms. Physical descriptions of each stage are below.

Image: PSHB life cycle ©Western Australian Government

Eggs

Eggs are 0.3mm long. They are laid individually or in clusters and hatch in 4 to 6 days.

Larvae

Larvae have a white, c-shaped, legless body with a dark head. They grow to around 3.5mm long and 1.1mm wide.

After 16 to 18 days, they will pass through 3 developmental phases called instars, then pupate.

Pupae

Pupae are white and around 1.5 to 2.5mm long. They will stay in this stage for 7 to 9 days while their bodies mature.

Adults

Adults are dark brown and around 1.5 to 2.5mm long. Females are larger than males.

The beetle’s life cycle from egg to adult takes around a month, but this can be affected by the host tree and temperature.

The larvae, pupae and male adult stages all happen inside the same tree.

Only female adult beetles leave to find a new host tree. When she finds a suitable tree, she bores a tunnel into it and lays eggs.

PSHB carries the fungal disease Fusarium euwallaceae. This disrupts the tree's vascular system.

Infestation of this fungus can lead to:

  • wilting
  • dieback
  • tree death.

For more information about host tree species, read the global host list PDF (649.4 KB).

Signs of PSHB infestation in trees

Tree monitoring is crucial for early detection and vital to eradicating the beetle.

Below are some signs of a PSHB infestation in trees.

Branch dieback

In susceptible trees, the fungus kills tree tissue causing branch dieback and tree death.

Image of tree dieback, showing a tree with green leaves on the left side and dead empty branches on the right.

Image: Tree dieback ©Western Australian Government

Multiple entrance holes

The beetle will create holes 0.85 mm in diameter, the size of a ballpoint pen tip.

Image of a large tree branch with hundreds of small entrance holes created by the beetle. The holes can be hard to spot.

Image: Multiple entrance holes ©Western Australian Government

Excessive frass

Frass is small bits of wood and insect waste produced by the beetle's tunnelling. Frass can look like sawdust or noodles.

Image of excessive frass, a light-coloured, fuzzy substance coating the tree branches.

Another image of excessive frass. It resembles textured, short yellow noodles coming out from the tree bark.

Images: Excessive frass ©Western Australian Government

Thick resin or sap

Thick resin or sap may come out from entrance holes.

Image of a tree branch with over 30 entrance holes and thick, brown resin and sap coming out of them.

Image: Resin or sap ©Western Australian Government

Sugar volcano

Crystal-like foam may spill out from entrance holes.

Image of a sugar volcano, with white, crystal-like foam spilling from the beetle entrance holes.

Image: Sugar volcano ©Western Australian Government

The beetle spreads through human activity and natural ways of spreading.

To search for a new host tree, female adults can fly up to 40 m and be carried up to 400 m by wind.

People can inadvertently spread the beetle by moving infested:

  • living plant material
  • firewood
  • green waste
  • woodchips
  • timber packaging
  • furniture.

PSHB can survive for months in cut wood, also known as felled wood. This is a major way infestations spread over large distances.

Report PSHB

If you think you have seen polyphagous shot-hole borer in the NT, contact either:

Submit a sample

You can submit a specimen for identification to Department of Agriculture and Fisheries Entomology at Berrimah Farm, either by mail or in person.

To prepare your sample:

Read more about pest sample submissions.

Send by mail

Entomology Section
Department of Agriculture and Fisheries
GPO Box 3000
Darwin NT 0801

Deliver in person

Combined Science Services Building, Berrimah Farm
29 Makagon Road
Berrimah NT 0828

Contact

For more information, contact Department of Agriculture and Fisheries Entomology:

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