What is PSHB?

Polyphagous shot-hole borer (PSHB, Euwallacea fornicatus) is a tiny (approx. 2mm long, the size of a sesame seed) invasive beetle native to Southeast Asia that attacks a wide range of trees and plants, with over 500 documented globally to have been affected. 

The beetle excavates tunnels, or galleries, in the trunks and branches of trees. It introduces a Fusarium fungus into these tunnels which it uses as a food source. The fungus spreads inside the trees, disrupting the plant’s vascular system and the flow of water and nutrients, which may lead to tree death.

How to detect infested trees 

Reproductive host tree species are those proven to support PSHB reproduction and allowing the growth of the associated Fusarium fungus, which serves as food source for the beetle offspring.

Popular reproductive hosts (susceptible trees) include Box Elder Maple (Acer negundo), Plane (Platanus), Poplars (Populus), Oak (Quercus), Avocado (Persea), Fig (Ficus), Black Locust (Robinia), Willow (Salix), Mulberry (Morus), Poinciana (Delonix regia) and Coral Tree (Erythrina).

A list of host tree species in WA where the beetles have successfully reproduced is accessible via dpird.wa.gov.au/PSHB.

Common signs to look for include:

  • Beetle entry/exit holes - approximately the size of a ballpoint pen tip.
  • Galleries - when pruning branches or inspecting fallen branches, check for evidence of galleries caused by the tunnelling action of PSHB beetles.
  • Discolouration/staining - this is caused by the Fusarium fungus.
  • Gumming - thick resin or sap.
  • Frass - produced by the beetles tunnelling, frass may be seen on the tree exterior. This can indicate a high level of infestation.
  • Sugar volcanoes - crystalline foam is exuded from entry/exit holes.
  • Dieback and tree death - the fungus disrupts the tree vascular system causing dieback and death.

How to report 

If you see signs of the borer or any other pests, report them as soon as possible via the MyPestGuide® Reporter app or contact the Pest and Disease Information Service (PaDIS) on 08 9368 3080 or padis@dpird.wa.gov.au.