Can this fungus turn the tide on coastal weed that spread from Geraldton to Sydney

A fungal super weapon has been released on Tasmanian beaches which could turn the tide in the fight against one of Australia's worst weeds.

Key points:

Sea spurge is an invasive weed from Europe which has spread uncontrollably across Australia's southern coastline

The plant is too widespread to be hand weeded or controlled with pesticide

The CSIRO has tested a fungus from the plant's native habitat in France, which is set to be released on Tasmanian beaches

The weed is called sea spurge: It's a small succulent shrub that looks like a lot of other native coastal vegetation.

It came to Australia from the coastal regions of France and swiftly took over the coastline from Geraldton in Western Australia, south and around the coast towards Sydney.

Since 2007 volunteer John Marsden-Smedley has been fighting a losing battle against sea spurge in Tasmania.

He and a team of volunteers have pulled out 14-and-a-half-million plants from Tasmania's beaches, but that's hardly put a dent in the population.

"Here on the north coast of Tasmania, there's 100's of millions of plants on this one beach … it's just soul-destroying," Mr Marsden-Smedley said.

"We've spent 8,000 days removing the weeds, that's worth nearly 2.2 million in volunteer hours alone, and that's just one beach.

"In the area we've weeded, we've reduced the presence of the plant by 99 per cent, but everywhere else, we've already lost the war."

Along the NSW south coast the weed reinvades sand dunes, as the seed travels on the sea. According to the CSIRO, spurge is affecting threatened native fauna and flora and Aboriginal heritage sites.

We will fight them on the beaches 

The fungus that's set to take the fight to sea spurge is called Venturia paralias and was discovered by research teams on the coast of France.

The CSIRO is releasing the fungus on three beaches in Tasmania to see if it will thrive in Australian conditions. (ABC Rural: Luke Radford)

CSIRO researcher Dr Gavin Hunter has been testing it since 2017.

"Initially the fungus infects the leaves, which can create a lesion on the leaf, but more importantly it can move from there into the stem," Dr Hunter said.

"Once in the stem, it produces a characteristic dark lesion on the stem, which makes it very difficult for the plant to transport water up and down the stem.

The fungus Infects the leaves and stem of the plant, causing lesions which can eventually make it collapse. (Supplied: CSIRO )

"It affects the plant's ability to photosynthesise and we're confident that it'll affect its ability to reproduce.

Dr Hunter said there's no danger the fungus will attack other species. Once the fungus takes control it weakens the spurge plant to the point of collapse. (SUPPLIED: CSIRO )

"Our testing has occurred over a period of a few years: We've tested it against a large number of related species," he said.

"We've found it to be highly specific."

Turning the tide

Back in Tasmania, Venturia paralias has been released on three separate beaches as part of the pilot program to test if it would spread and thrive in Australian conditions.

Mr Marsden-Smedley has overseen the release of the fungus, he said it gave him great hope for the future. 

"I've been walking and working on the Tasmanian coastline for the best part of 40 years," he said.

"I'm really looking forward to being able to go back to those areas and not think that they're immediately at threat. 

John Marsden-Smedley has been leading the fight against sea spurge in Tasmania, now he's releasing the bio-control. (ABC Rural: Luke Radford)

"The areas that I frequent are part of the world heritage area, it's an area that's reserved for its ecological and cultural values, and I like to see it stay that way." 

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