Home       The Wilding Threat     About WELRA       Getting Involved     Publications      Links      Contact WELRA

News Update July 2009

Herbicide Wilding Control Trial
Herbicides are an obvious tool to control dense areas of wildings.  However past spraying has given variable and often disappointing results.  DoC Otago is carrying out extensive trials with a range of systemic chemicals that are translocated throughout the trees.  Unfortunately these chemicals can also cause considerable “collateral damage” to any nearby native plants.

Rather than repeating the Otago trial work in Canterbury, some new contact chemicals have been trialled on Flock hill which should be less damaging to native species.  Several applications may be required since contact chemicals can’t physically cover every green needle on a tree with one pass.  (This may still be cheaper than mechanical clearing that can cost over $12,000/ha)

Wilding spray trial
Helicopter carries out a wilding spray trial near the site of the Narnia film.

Trial / Demonstration Details.  About 9 hectares was covered in March 2009

  • Chemicals and additives were at three different rates of  X-change, Superquik, Diquat, Desicate, Hammer and Du Wett and/or Aqua-gel using a specially equipped helicopter. 
  • A range of species and tree sizes were treated
  • Spray was applied by helicopter at a water rate of 500 litres per hectare. 
  • There are minimal spray drift risks with large droplet technology used.
  • All chemicals are contact killers with no residual effect in the soil.
  • Spraying will leave dead standing trees which can encourage native plant species to establish below in the shelter and shade of the dead trees.  Beech trees could be planted into this sheltered microclimate.  (This way of encouraging native regeneration is being used successfully in the Marlborough Sounds where they poison individual large trees).

Trial Funding

  • WELRA would like to acknowledge the funding and support for the trial which came from Land information NZ, Environment Canterbury, Flock Hill Limited.  The work was carried out by Amuri helicopters and Andy McCord of Technical Forest Services Ltd.

Native Cassinia
Trials of new contact herbicides seem to be causing little damage to native Cassinia, ground cover plants and tussocks at this stage.  


  • It is too soon to assess; This will be done after the winter snows.
  • Upper needles have been effectively removed but green needles at the base of larger trees have escaped contact with the chemical.  Another application may be needed once upper needles have fallen.  This initial spray is likely to prevent coning and seeding for at least 3 years.
  • Damage to many native plants looks slight at this stage.

Ancient Grasshopper Habitat to be protected

The WWF – Habitat Protection Fund has granted WELRA $10,000 towards developing a management plan and undertaking control in the Broad Stream catchment. The rare dinosaur-aged grasshopper, Brachaspis “Broad Stream”, three species of endangered plants (Kirks broom, Waimakariri Helichrysum and Walls Coprosma) and native riverbed birds are all under threat from spread of wilding conifers in Broad Stream. Local landowners, Rangiora Tramping Club, tourists & conservation volunteers have been involved in the control of wildings in this area for the last 12 years. Each year thousands of seeds rain down on the river bed from seeding Douglas Fir trees on rock outcrops above. These source trees require specialist control; the work is too difficult & dangerous for volunteers. This funding will allow WELRA to hire contractors to undertake control of source trees on the bluffs.

Can you spot him?

WWF for a living planet

$136,000 for Flock Hill Management Plan wilding control (Update: May 2009)
Success with recent funding applications has seen WELRA receive $136,000 to undertake priority control works outlined in the Flock Hill Management Plan.

Successful applications were made to the Lottery Environment and Heritage Grants ($96,000) and the Canterbury Community Trust environment section ($40,000). This is a fantastic boost to the ongoing work of many volunteers, landowners & members of the alliance.

Environment Canterbury hopes to allocate $50,000 towards control work on Flock Hill from the Regional Pest Management Strategy

WELRA would like to thank all these groups for their support.