Open Knowledge (FSC OK)

The Forest Stewardship Council (FSC), a forest eco-certification body, has prohibited key herbicides used in forest vegetation management, including two of the main herbicides used in New Zealand (hexazinone and terbuthylazine). Using New Zealand as a case study we (i) review the basis of the prohibitions, and (ii) compare the financial viability of current practice (using aerial and spot control of weeds with prohibited herbicides) with alternative FSC compliant chemicals (applied aerially or using spot application), and non-chemical control methods (weed mats, mechanical, manual control). Low values of the distribution coefficient (Kd) were found for hexazinone on a range of New Zealand forest soils. This supports the FSC ban of this herbicide based on its high mobility. Values of Kd were relatively high (average 19.7 L kg -1) for terbuthylazine across a range of New Zealand soils indicating limited mobility for this herbicide. Terbuthylazine is banned because it has the potential to bioaccumulate. We contend that in situ breakdown in some New Zealand forest soils will reduce the risk of bioaccumulation. Assuming no losses in crop growth, analyses indicated that use of FSC compliant herbicides is likely to be a cost effective alternative. Analyses show non-chemical control methods are not cost effective in New Zealand.