Conifer infestation containtment for Queenstown Hill

A campaign will get underway next week to contain the creeping infestation of wilding conifers on the iconic reaches of Queenstown Hill, Queenstown Lakes District Council district forester Briana O’Brien said.

“Wilding conifers pose a threat to the unique landscape and the native vegetation of the Queenstown Lakes District, containment of this threat on Queenstown Hill is one of the actions set out in the Wakatipu Wilding Conifer Strategy,” she said.
Control of the infestation would be undertaken by helicopter application of herbicide spray, next week.
“The 30 hectare zone being targeted is private rural farmland, well away from any urban area,” Ms O’Brien said.

Queenstown was renowned for its visual landscapes; the wilding component could very rapidly and significantly change that.

“Left unmanaged, the various species such as Douglas fir will dominate tussock land replacing the natives with a dense impenetrable forest of pine trees. This takes away the opportunities that we currently enjoy with our indigenous flora and fauna and the open high country tussock scenery,” she said.

Management was essential for the long-term interests of New Zealand’s premier resort town.
“Queenstown Hill is a high priority management unit in the strategy because it’s commonly used for recreation purposes and is highly visual throughout Queenstown, if the wildings are permitted to continue tracks would become increasingly shaded and views towards the mountains and the lakes would be lost.”

The goal of the operation was to create a containment line by spraying the dense infestation of pines. This method has already been used with success by DOC at Mount Aurum Reserve and the mouth of Lewis Creek (Long Gully). The strategy had seen a major investment with total expenditure from 2004-2008 by QLDC, DOC and landowners of approximately $1 million.

The cost of the Queenstown Hill job was estimated to cost $18,000, to be divided evenly between QLDC, DOC, and the landowner.

“The establishment of the containment line means that future efforts will concentrate on keeping the area above the line clear of pines,” Ms O’Brien said.

A short term drawback of the spray was the unsightly and obvious strip of standing dead trees, however this was a small price to pay compared with the potential dispersal of millions of seeds which would cover the landscape.

“Wilding control work has been carried out for many years around the district, normally out of view, but because the Queenstown Hill work is more visible to the public it will create a greater need for awareness,” Ms O’Brien said.

 

The Wakatipu Wilding Conifer strategy is available on the QLDC website.

ENDS

A fact sheet follows

QUEENSTOWN HILL WILDING CONIFER CONTROL
Wildings

Introduced species of trees pose a threat to New Zealand’s biodiversity and landscape values in a similar way to possums, rats and didymo. Like other introduced problems, wilding trees have no natural control in New Zealand and thrive in our conditions found here. Douglas fir can grow at altitudes well over 1600m. Our natural tree line is around 1000m.

A mature pine can produce many thousands of seeds per annum and under the right conditions can travel several kilometres.

What are the main problem species on Queenstown Hill?

douglas fir and European larch
How long has control been going on?

The landowner and organisations have been engaged in wilding control on Queenstown Hill since the early 1980’s. The current containment method started in 1990.

Have other methods been tried?

Many different control methods are used, including chainsaw gangs, gangs using hand saws and axes, volunteers, ground spraying.

What chemical is used?

‘Roundup’ (Glyphosate) and ‘Answer’ (Metsulfuron) applied via a helicopter boom. Both the chemical and the method of application are commonly used in agriculture and all approved safety standards will be met.


Are there any health issues or concerns?

No, the boundary of the spray zone is a minimum of 500 metres away from any urban dwelling. The spray will only be applied in optimal conditions and application will be closely monitored. The application will not affect the residential area.
Does this method work?

Trials have been conducted with different chemical and application methods and the results indicate that this method is worth using over larger areas.

Will indigenous flora and fauna be affected by the spray?

Wild pine forests do not support a significant amount of indigenous flora or fauna, one of the reasons for stopping their spread. However, it is always possible that some damage to native species could occur; matagouri and tussocks on the immediate fringe from overspray. QLDC staff, DOC staff and the landowner will monitor on-site during spray operations.

Will water supplies be affected?

Spray operations will be undertaken in such a way as to minimise impacts on waterways.

No water tanks on Queenstown Hill will be affected as they are well outside the spray area. The tanks are enclosed and are fed by a closed system which originates from the Two Mile intake at Fern Hill reservoir.

How much of the area will be sprayed?

A strip approximately 100m wide and 3km long around the top of Queenstown Hill. Total area approx 30Ha.
How long before the trees die?

It will take up to two years for all the sprayed trees to die. It’s not known how long they will stay standing dead as it varies, depending on annual rainfall, relative humidity, aspect of the slope the tree is on – they all contribute to the dead tree’s breakdown.

Is spraying a better option than felling?

The cost of felling these areas is prohibitive. Costs to manually fell trees by chainsaw can go as high as $8,000 per hectare. The planned spray programme is likely to cost less than $1,000 per hectare. Also standing dead trees provide a better climate for more suitable vegetation to re-establish.