The Mid Dome Wilding Trees Charitable Trust and Environment Southland want volunteers to help clear areas where rogue pine trees have become established.
Trust member Richard Bowman said volunteer events were held twice a year, to clear areas where pine was scattered.
On a good day, volunteers could clear as much as 5ha, he said.
''The aim is to get as many people as we can to actually see the spread ... it's a very graphic way of showing people how big the problem is.''
The trust was established in 2007 to manage the spread of wilding pine. Since then, about 1000ha of closed canopy forest has been cleared from the 68,602ha Mid Dome area.
Wilding pine had been controlled over 31,000ha in the project area over the past five years.
About $10 million had been spent and another $10 million would be needed to satisfactorily control the spread over the next 10 years, he said.
It was predicted wilding pine could overwhelm 61,000ha of high country tussock and pastoral grassland in the area, and infest a further 100,000ha, by 2053 if left alone.
Environment Southland biosecurity and biodiversity operations manager Ali Meade said there was commercial value in pine ''but when the trees seed, the wind picks it up and can blow it into neighbouring properties or upland conservation estate or native forest''.
However, there is no commercial value in the wilding pine, she said.
''The right tree, right place'' approach was used, which meant some areas in Southland were marked for being at high risk of wilding seed being spread by wind into an undesired area, she said.
People wishing to volunteer on November 23 were asked to visit the trust website or contact Environment Southland.
