The 77-year-old would spend a day or more a month cutting the dense thorny weed from the outside in, before climbing underneath to remove the aggressive invader from the ground.

It was quite literally a thorn in his side.

Today his widow Carmel James is carrying on his work, as she continues to regenerate their property.

"The thorns are about three inches long, they are very sharp, and to cut it off you've got to climb in underneath it, which is almost impossible because the branches go down to the ground."

"It's a nightmare, absolute nightmare," she said.

The weed poses a similar problem for her neighbour John Calokerinos.

He runs up to a hundred cattle on his 500-hectare property, where the boxthorn is a problem.

"It's a hell of a lot of work ... they're so dense," he told AAP.

"To spray them you need to use these horrible chemicals and it's under existing trees where you have a bit of understory, and then you're killing everything under or around them."

"Where there are trees you're guaranteed to get boxthorn come up under them," Mr Calokerinos said.

The African boxthorn was introduced to the country in the mid-1800s as a hedge plant but has since infested vast tracts of land in southern Australia.

But that could soon change thanks to a biocontrol agent introduced to target the weed.

A fungus and natural enemy of the invader has been brought to Australia from South Africa and grown by CSIRO scientists.

Under the NSW government funded program the fungal spore packages will be sent to landowners for release across the state

But with a failed biological control in the cane toad still causing havoc across parts of Australia, scientists are cautious.

"This has to be done with the utmost safety in mind," Ben Gooden from CSIRO's weed biological control program said.

Multiple tests have been done to ensure the agents won't threaten any native species.

"The CSIRO would never apply for the release of these organisms to the federal government regulators unless we had the data available to show they pose negligible risks to the Australian environment."

The researchers will also release an aquatic weevil that eats it way through another invasive species, the water weed cabomba.

Introduced in Australia in 1967 as an aquarium plant it has spread from Cairns to Melbourne since escaping.

Both the pathogenic rust fungus and water weevil will be released over the next three years in NSW.

Invasive weeds threaten 40 per cent of endangered or vulnerable species according to NSW Environment Minister Penny Sharpe.

"When successful, biocontrol is highly cost-effective, with overall economic returns of $23 for every dollar invested," the minster said.

CSIRO is now looking for landowners who might benefit from the biocontrol agents.

"This is about community engagement, working with farmers to be engaged and partnering with us on the ground to control these plants," Dr Gooden said.

The invasive species council has backed the initiative, and would like other states to follow.

"The benefits from biocontrols are massive ... for these weed species that are well established, it's often the only way to really do something about it," the council's CEO Andrew Cox said.

Australian Associated Press