Wilding conifers growing in the Wakatipu district will come under attack in a large-scale aerial spraying campaign.
Following the success of a 30ha trial spraying programme last year, the Queenstown Lakes District Council will launch a bigger campaign in early December.
A mixture of agricultural chemicals will be sprayed from a helicopter in a bid to continue the conifers "containment line" around to the front of Queenstown Hill, and into other areas of the Wakatipu Basin.
The helicopter will be fitted with nozzles designed to minimise spray drift.
The chemicals - Roundup, Answer and Grazon - and the method of application are commonly used in agriculture. The main problem species targeted will be Douglas fir, European larch and contorta.
QLDC district forester Briana Pringle said the wilding conifers posed an "enormous threat" to the Queenstown landscape and native vegetation.
"Left unmanaged, the various species such as Douglas fir will dominate tussockland, decimate the natives and put an end to open high country tussock scenery."
Ms Pringle said specific dates for the operation have not been decided yet - the operators wanted "perfect weather".
In accordance with the Wakatipu Wilding Conifer Strategy, the spray operation is a joint venture by the council, the Department of Conservation, landowners and the Wakatipu Wilding Conifer Control Group.
It is funded by the partners and the Lotteries Commission.
Ms Pringle said trials had been conducted using different chemical and application methods and the results indicated the aerial spray method was worth using over larger areas.
During the operation, the council expect some damage could occur to native plant species, but Ms Pringle pointed out wild pine forests did not support a "significant amount" of indigenous flora or fauna.
Queenstown Hill will be closed to the public when the hill is sprayed.
The planned programme is likely to cost less than $1000 per hectare and it will take up to two years for all of the sprayed trees to die.
The high priority areas include Queenstown Hill, Von Valley, Long Gully, Gooseberry and Horse Gully, Arrow River, Mt Aurum recreation reserve, Five Mile Creek, Waitiri, Gibbston and the front faces of the Remarkables Conservation Area.
