Murdoch researchers identify new dieback species

Murdoch researchers have identified a new dieback species in tuart trees, long believed to have escaped the killer plant disease.

PhD student Peter Scott said scientists had identified the new dieback species Phytophthora multivora last year in the Tuart Forest in Yalgorup National Park, south of Mandurah.

“It’s part of a group of organisms that are the worst plant pathogens (an agent that causes disease) in the world,” Peter said.

“It constantly weakens the tree so they become more susceptible to other diseases.

“It is a bit like AIDS in that in the end they will become more susceptible to other illnesses and it’s those which eventually kill them.”

Tuart trees in a 10km square radius of the park - which covers 13,000 hectares of a narrow stretch of coastal land and is home to 10 lakes - have been identified as infected with the dieback species, he said.

The Swan Coastal Plain of WA is the only place in the world the tuart occurs naturally.

Peter said he suspected the dieback was there based on the way the trees were dying.

“In parts of the Tuart Forest, we have 50 per cent mortality,” he said.

“A lot of the trees are dead and of the ones that aren’t, you can see they are on the way out.”

Peter, who, along with a team of Murdoch researchers has worked on the project for the past three years, said the soil tuarts grow in is calcareous - like crushed limestone.

Since the 1970s, scientists believed the tuart had escaped the predominant dieback species Phytophthora cinnamomi, which affects 40 per cent of plant species, including jarrah trees.

The theory was that Phytophthora cinnamomi didn’t flourish in the soil found on WA’s coastal strip.

But Murdoch researchers’ findings have proven that incorrect.

He said it can take decades for symptoms of the disease to show in trees – and it can take decades to kill one.

More research and funding were needed to identify the entire infected area.

“I think we have a social right to do right by the tuart tree because we have bulldozed a lot of their natural habitat for residential development,” Peter said.

There were some measures scientists could take to fight the disease, such as injecting the infected tree or spraying the entire forest with the chemical phosphite.
Replanting the forest was another option.

Peter’s findings have just been published in the international journal Persoonia.