When Perth resident Joanne Taggart noticed unusual insect damage in some fallen branches after a storm, she was curious. Within minutes of reporting it via an app she’d heard about on a radio gardening show, she received a phone call that would set off a large-scale community and government response. The culprit? The polyphagous shot-hole borer, an invasive beetle threatening Western Australia’s environment and amenity trees.
The borer may be a tiny insect, but its effect on trees is devastating. The beetle burrows into trunks and branches, creating tunnels where it cultivates a fungus that disrupts a tree’s ability to transport water and nutrients. This fungus, which the beetle uses for food, can quickly weaken and kill a tree, making early detection crucial.
A tiny beetle with a big impact
Taggart’s discovery of the beetle in August 2021 kickstarted WA’s fight against the pest. The affected tree, a box elder maple, was later identified as an “amplifier tree” – a tree, or species of trees, particularly attractive to the borer as a reproductive host. As a keen gardener, Taggart had downloaded the Department of Primary Industries and Regional Development (DPIRD) MyPestGuide Reporter app for fun, not realising she would play a crucial role in the beetle’s detection.
“I’d never seen tunnelling like this before,” she says. “When I sent in the photo, I got a call back within 10 minutes and biosecurity officers from DPIRD came to my house later that day to inspect the tree.” The team confirmed the beetle’s presence and quickly arranged for the tree’s removal.
Losing the tree was more than just an environmental concern for Taggart; it was deeply personal. “I was very upset about losing it,” she says. “It’s amazing the impact losing trees in your garden has on you, especially when they’ve been there a long time.”
The rear of the Taggarts’ family home faces north to the garden and is predominantly glass to make the most of the views, so the removal of a tree 12-14 metres tall has changed the outlook significantly. “That tree was part of my life for 40 years; I planted it myself,” Taggart says. “My son had his wedding photos taken under the tree and my granddaughters had their birthday parties there.”
The dappled shade that the deciduous tree provided in summer also vanished with its removal. “The temperature in the back room of my house is now five degrees higher, just on a regular day.”
Since the discovery, government departments, community groups and residents have mobilised to contain the pest, and to get the message out to people across Perth about the importance of keeping the spread of the polyphagous shot-hole borer under control.
Initiatives such as National Biosecurity Week draw attention to the importance of controlling pests. Running from 25-31 August, it highlights the collaborative efforts that help protect our environment, agricultural industries, food supply, communities and overall economy.
Sue McDougall, the director of the Western Australian Botanic Garden, says her team has been working closely with DPIRD in response to the discovery of the borer to identify and remove affected trees and shrubs.
“We have a fantastic relationship with DPIRD,” McDougall says. “It’s about working together and reacting quickly, and getting the right information out there so people understand the threat and know what to look for.”
Educational initiatives and surveillance have been fundamental to the response effort. Volunteer groups, tree advocates and garden centres have been involved in raising awareness. “When people go to buy trees, they’re getting advice on species that are resilient to the borer,” McDougall says.
While research is ongoing, species proving most resistant to the shot-hole borer in WA include natives such as jarrahs, banksias, wattles and bottlebrushes.
The importance of early detection cannot be overstated. Once a tree is infested, there is no known chemical treatment for the borer, so managing its spread through tree removal or pruning is important.
A $2.17m research initiative launched by the WA government may help the fight against the borer. It includes funding for three new projects aimed at developing innovative solutions to the problem. These three-year projects will focus on key research priorities such as improved control strategies, detection and surveillance methods, and better understanding of host biology and interactions in the WA environment.
Early reporting is key
Residents are encouraged to regularly inspect their trees for signs of the borer, including limb failure, dying leaves and tiny pitted holes in the bark. Particularly vulnerable trees are box elder maples, coral and flame trees, robinias, London planes and many others. “If plants are losing their health and vigour in your garden, take a closer look – that’s probably your first indicator,” McDougall says. “If you see something unusual, report it, because the earlier we detect it, the better chance we have of slowing the spread.”
The MyPestGuide Reporter app has been instrumental in gathering real-time data. Since 2021, millions of trees have been inspected, and the quarantine zone has been expanded to cover all of metropolitan Perth.
Taggart says the experience has changed the way she thinks about biosecurity. Wary of planting species that could attract the borer, she has yet to replace her lost tree. “I’d love to replant with native species, but I want to be sure they won’t be affected,” she says.
WA is continuing its efforts against the borer, with the aim of minimising the risk of spread beyond the Perth metropolitan area and protecting the state’s regions and horticultural industries.
Find out more about what to look for and how to report on the Department of Primary Industries and Regional Development’s website.
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