Deadly borer finds Aussie foothold in East Freo

AUSTRALIA’S biosecurity services are on high alert after an exotic polyphagous shot hole borer was discovered at an East Fremantle property. 

The borer Euwallacea whitfordiodendrus, credited with causing millions of dollars of damage to orchards and forests overseas, was found in a box elder maple tree in Dalgety Street after keen gardener Joanne Taggart noticed unusual insect damage in some branches brought down by a storm.

Using the WA agricultural department’s MyPestGuide app on her phone, Ms Taggart sent photographs and expected a response after a few weeks, as per normal when she snapped an interesting bug.

Tiny 

“Almost immediately, I got a phone call,” a surprised Ms Taggart said. “They sent someone pretty much straight away.” 

After the officer took away some samples, the department then sent down a team including an expert who checked “every little crevice and every little place” before triumphantly holding up one of the tiny borers. 

The department will now pay to have the tree removed right down to its roots, while the remnants of another that died last year are also being dug up. 

“I planted both of these trees nearly 40 years ago, so I’m very heartbroken to be losing them,” Ms Taggart said. 

“They actually used to meet right out there, so the whole place was just lovely dappled light,” she said, gesturing across her backyard. 

According to the Californian Society for Ecological Restoration, the borer has the ability to kill “hundreds of tree species” and is causing millions of dollars of damage, “devastating” native woodlands.

It does so by boring into a host tree to lay eggs which then feed on a fungus the beetle brings with it. 

It’s the fungus that’s the real villain, as it affects the hosts’ ability to circulate water and nutrients, causing stress, dieback and death in extreme cases.  

The Department of Primary Industries and Regional Development released a media statement on Thursday afternoon saying the beetle was considered an agricultural and environmental pest. 

If uncontained, the borer could cause substantial harm to forestry and fruit-tree industries, according to the statement. WA’s native forests could also be severely impacted. 

Californian researchers Mary Lu Arpaia and David Obenhand visited an Israeli orchard five years after the borers became established and reported: 

“Severe limb dieback, many broken branches scattered on the orchard floor, dropped mature fruit and smaller than normal fruit size for the fruit remaining on the trees.”

Jacarandas

Common victims of the borer include jacarandas, red flowering gums, acacias and ficus. 

Department chief biosecurity officer Sonya Broughton encouraged the Fremantle community to remain vigilant and report any sign of the borer.

“These include multiple entrance holes on the trunk or branches that are approximately the size of a ballpoint pen tip,” Dr Broughton said. 

“Other signs to look out for are thick resin or sap on the tree branches or trunk, dark brown to black staining of the wood around entrance holes and dying branches.”

Additional symptoms include frass, which is an insect excretion, as well as crystalline foam which look similar to sugar volcanos that come from the entry holes. 

To add to the department’s concerns, East Fremantle council’s green waste collection begins this Monday, September 20. 

Residents are advised not to remove any green waste material and wood, and instead to leave it for the council collection. The department also urged the public to inspect their trees for symptoms of borer damage. 

The beetle is known to have affected avocado orchards in parts of Israel, South Africa and southern California and has not been detected in Australia until now. 

Ms Taggart praised the department for its app and its swift response: “I think it’s great; all credit to the department for putting it out there,” she said.

Officers scoured Ms Taggart’s backyard but couldn’t identify anything that would have brought the borer in. They also inspected properties up and down Dalgety Street looking for signs of the borer, which is known to fly up to 400 metres to find a new host. 

The department thanked Ms Taggart for her vigilance.

by KATHERINE KRAAYVANGER

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