About 35ha of conservation land is being targeted and $20,000 of Doc Wakatipu funds has been set aside for the latest assault in a long campaign in the valley officially known as Mt Aurum Recreation Reserve.
''It's part of a wilding pine eradication and removal project going on for more than 10 years to protect the outstanding natural landscape and gold-mining heritage,'' Jamie Cowan, Doc Wakatipu biodiversity threats ranger and Wakatipu Wilding Conifer Control Group operations manager, said yesterday.
''Several hundred hectares have been done over the last few years and we're getting down to the nitty gritty.
Mr Cowan said the aim was to return the valley to the state it was in more than 100 years ago, when it had no exotic trees. Areas near the historic Skippers School would not be sprayed. There were some species of pine which did not spread and added character and shade to the reserve, he said.
Mt Aurum Recreation Reserve will be closed to the public for wilding pine operations from Sunday morning and will reopen the next day.
Concessionaires had been advised and ''understood the bigger picture'', Mr Cowan said.
Residents would not be affected. Signs were posted at Skippers saddle yesterday, the entry to the valley from the Coronet Peak access road.
Mr Cowan said a common herbicide named Answer would be applied by boom spray on a helicopter. Spraying would not be applied to waterways and measures were in place to stop spray drifting.
It will be safe to re-enter the reserve on Monday once the herbicide had dried.