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Aggressive control of large seeding trees across the lower front faces of Mt Dewar Station is needed to stop their spread and protect the golden tussock faces of Mt Dewar, Skippers Saddle and Coronet Peak, the Department of Conservation (Doc) says.
The declaration came as Doc Wakatipu, on behalf of the umbrella charity Wakatipu Wilding Conifer Control Group (WCG), prepares for the latest battle in the war against introduced wilding pines which suffocate native biodiversity.
The $100,000 operation is funded by the station and WCG. The 160ha of private land to be treated is in addition to the 220ha already covered this year, well on the way to the 600ha target for 2014.
The operation was publicly notified and the Ministry of Health has been advised.
Work is expected to begin today or early next week, depending on the weather, and continue over the next few months.
Doc Wakatipu ranger and WCG operations manager Jamie Cowan said the method of control to be used was boom spraying via a helicopter. The herbicides to be used were common in agriculture, being standard, ''off-the-shelf'' products.
''The herbicide to be used on the Douglas fir and larch on Mt Dewar Station will be Metsulfuron [Answer],'' Mr Cowan said.
''Specially designed nozzles will be used on the booms and crop oil will be added to avoid the drift of spray to non-target areas.''
Mr Cowan said there were strict climatic restrictions on when aerial spraying could happen.
Spraying would only take place when the right combination of temperature, wind and humidity occurred. No aerial work would occur near waterways.
Mt Dewar Station had been fighting wilding pines for decades. There were only three pines in 1954 and wildings now covered many hectares of the station, particularly over the station's lower front faces.
The spread was a consequence of an increase in the seed source and the gradual reduction in stock numbers.
The rapid growth of wilding trees was now spreading through Devils Creek and threatening both Skippers Saddle and Coronet Peak, Mr Cowan said.
''The Mt Dewar wildings are really starting to dominate the landscape of the Wakatipu basin.''