Sydney Heritage Trees At Risk Of Beetle Attack

The chief scientist of the Sydney Botanic Gardens has issued a warning of a new biosecurity threat that has decimated thousands of trees in Perth.

The polyphagous shot-hole borer, native to south-east Asia, is only the size of a sesame seed, but carries Fusarium ambrosium fungus to sustain its larvae. This fungus spreads into the vascular system of the tree, blocking water and nutrient vessels, leeching the tree of hydration and energy.

The beetle was first noticed in Perth in 2021, where it had likely arrived via imported wood. It had spread to more than 200 locations across the city only a year later, and about 4,000 trees, including Moreton Bay and Port Jackson figs, have since been cut down in an attempt to stop the beetle’s spread.

In June, the WA government announced that a national management group had decided it extermination attempts were no longer liable, and have switched to management strategies.

“We’ve been concerned for the past couple of years, but that concern is now heightened because the potential for it to be accidentally brought into the Sydney region is quite significant,” said the Gardens’ chief scientist, Brett Summerell.

“I could imagine that you have people camping near Perth and then coming across the Nullarbor, driving to eventually end up in Sydney with some infested firewood. That’s one potential way it could get here.”

“Big experiment” just waiting to happen

It’s unknown how many types of trees in Australia could become infected, as the fungus can’t thrive in all tree species. Plane trees, which make up many of the trees in the CBD, are known targets, as well as figs and box elder maples.

Their loss could result in an urban heating spike of up to 12 degrees.

“It’s just a big experiment about to happen,” Summerell said.

Surveillance measures, such as traps that attract the beetle with pheromones, have escalated across the Botanic Gardens in collaboration with the Department of Primary Industries.

Summerell has urged people to familiarise themselves with symptoms of an infestation and report suspected sightings to the state’s biosecurity hotline.

“The more sets of eyes we have looking for potential problems, the more likely we are to find it early,” he said.