With so many weeds and pests already established on K’gari, it is important that we don’t inadvertently introduce more. One such group of pests are the shot hole borers.
What is it?
Euwallacea spp. or shot hole borers and their associated fungi are internationally significant pests threatening tree species of commercial, amenity and environmental significance. They are highly polyphagous (feed on a wide range of host species). The fungi they vector (e.g. Fusarium spp.) pose a considerable and increasing threat to a range of Australian subtropical and tropical horticultural industries and tree species of urban and environmental significance.
These beetles are part of a cryptic species complex, meaning different species are difficult to distinguish morphologically. However, they can be differentiated using molecular tools, and each species has different and variable fungal associates. They are variously native to Southeast Asia and the Pacific regions (see map). Polyphagous shot-hole borer (PSHB) Euwallacea fornicatus has spread to USA, Israel and South Africa. PSHB and its associated Fusarium euwallaceae are both listed as priority exotic environmental pests. As well as PSHB, within this complex, are the tea shot hole borer (TSHB), E. perbrevis, and Kuroshio shot hole borer (KSHB), E. kuroshio. Both of these species are also invasive in other regions.
Where are they?
In Australia, TSHB is present in Queensland and northern NSW. Unfortunately, the polyphagous shot-hole borer (PSHB) has just been detected in Western Australia and is currently under a biosecurity response. It has not as yet been detected elsewhere in Australia.
What’s the impact?
The host list is extensive, with over 100 “reproductive hosts“. In severe cases, the beetle attack and subsequent infection with the associated Fusarium fungus result in tree dieback and tree death.
In Queensland, the TSHB has been recorded causing dieback in avocado, and dieback and whole tree death in native tuckeroo (Cupaniopsis anacardioides). However, it has not been detected on K’gari with surveys conducted in native stands and planted trees around the townships (Eurong).
How does it spread?
Humans and their movements between regions are important vectors. Firewood is known around the world to be a primary form of spread into new areas. Therefore, to protect K’gari, we should not move any firewood from the mainland to K’gari.
The beetles can fly and transport the fungus. However, this is usually only a short distance and results in the localised spread of the beetle and fungus.
What to look for
The beetles are too small to detect easily. However, you can identify the infected trees. The symptoms of infected trees vary from one tree species to another, and there are many signs that a tree may be infected. Some of these signs are:
- Wilting trees
- Dead branches
- Exit/entry holes on the bark of the trees
- Shotgun-like lesions on the bark at entry/exit holes
- Sugar volcanoes on the bark at entry/exit holes
- Blotches of oozing resin on the bark at entry/exit holes
- Wood frass (wooden powder) on the bark at entry/exit holes
For more images, please click here. For more information on the environmental exotic pest list, please check out The National Priority List of Exotic Environmental Pests, Weeds and Diseases – DAWE.
Remember, if you see it report it – Exotic Plant Pest Hotline 1800 084 881
Article contributed by Geoff Pegg and Helen Nahrung, Department of Agriculture and Fisheries