Reducing the use of herbicides in forestry (Scion)


  • Environmental certification by the Forest Stewardship Council (FSC) allows New Zealand forest companies access to value-added markets and offers a means of attracting investment from the global financial sector.
  • Trees cannot survive if aggressive woody weeds such as gorse, broom, bracken, and buddleia are not controlled.
  • Access to cost-effective herbicides is critical for the ongoing commercial viability of plantation forests. Two important herbicides, terbuthylazine and hexazinone, have been designated as “highly hazardous” by FSC and cannot be used in certified forests unless a derogation has been obtained. .

Potential benefits/cost

Cost effective weed control provides an economic benefit of between $80 and $100 million a year.

Data from 2004 indicate that hexazinone and terbuthylazine were the two most important forest herbicides.

Losing these herbicides before alternatives are found would cost the industry their choice between certification and use of non-chemical control methods.

Non-chemical methods of weed control could increase the cost of establishment from $750 to over $2000/ha, assuming labour was available, and also result in long term losses in productivity, exacerbating this cost.

The cost of current weed control research is approximately $500k/yr.


Scion’s work on the behaviour of terbuthylazine in forest soils has directly supported the ongoing use of the herbicide.

A project is underway to trial new and short-listed alternatives across a range of weeds and sites.

Chemical control options will be trialled in combination with non-chemical control methods to establish successful operational prescriptions for use by all industry.

Certification-compliant weed control (NZ forest industry retains licence to operate in global market.)

Scientifically proven risk profiles for prohibited herbicides.

Cost effective weed management strategies for the New Zealand forest industry.


Research into herbicide reduction underpins one of the most critical components of the whole forest products lifecycle, namely the economic establishment or re-establishment of commercial forest plantations. Scion is ensuring the sector has ongoing access to cost-effective herbicide treatments, ensuring the ongoing viability of forest establishment.

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