Özet:

Wilding conifers are a major threat to large areas of land throughout New Zealand where they compete with native vegetation, modify ecosystems, reduce available grazing land, limit future land-use options and visually change landscapes. Wilding conifers can also enhance damaging fires and in water limited catchments can affect surface flows and aquifer recharge.A range of herbicide treatments was aerially applied by boom to a field trial established within a wilding Pinus contorta (Dougl.) (height range 1.5 – 12 m) infestation. Measurements of mortality taken two years post herbicide application were used to examine variation in efficacy of these herbicides using a mixed-effects model that tested the main and interactive effects of tree height and herbicide treatment on mortality. For a treatment to be considered effective, a mortality rate of over 85% should be achieved.Findings: Herbicide treatment was found to significantly affect mortality. Application of herbicides that included triclopyr (18 kg a.i. ha−1) and dicamba (5 kg a.i. ha−1) applied in combination or these active ingredients applied with picloram (2 kg a.i. ha−1) were found to effectively control P. contorta across the treated height range inducing respective mortality rates of 88 and 89%. Tree mortality rates for these two herbicides were significantly greater than for two treatments with only triclopyr (37%) or triclopyr and picloram (66%) used at the previously stated rates. Neither height nor the interaction of height and treatment affected mortality over the tested range of heights.Conclusions: This research has shown that dense infestations of P. contorta can be successfully controlled using aerial broadcast application of triclopyr-based herbicides applied in a high volume (400 L ha−1) mixture, with extremely large droplets (400 – 500 μm). The Department of Conservation has adopted the most effective formulation for operational use.

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