Aerial herbicide spraying to control wilding <i>Pinus contorta</i> in New Zealand

Authors: Stefan Gous, Peter Raal, Michael Watt
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2012, Issue N.Z.J.For. 57(2) 2012, pp 35-37, Aug 2012
Publisher: New Zealand Institute of Forestry

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Abstract: Abstract There is not much information on aerial application of herbicides to control wilding conifers in New Zealand. Two South Island study sites infested with dense Pinus contorta were selected to conduct trials testing the efficacy of aerial application of various herbicide combinations. Four herbicide treatments were applied as a randomised complete block of three replications at each site. Herbicides were applied by helicopter during January 2011 using a boom spraying system calibrated to deliver 400 l/ha. Spray efficacy was determined by measurements of percentage of dead foliage (damage) and mortality 12 months post treatment. Of the four herbicides tested the most effective included 18,000 g triclopyr, 5,000 g dicamba, 2,000 g picloram and 2,300 g ammonium sulphate in an application volume of 400 l/ha. For this treatment tree mortality and damage were respectively 86.6% and 98.6%. Because the systemic herbicides tested here are only effective during the active growing season it is anticipated that mortality may increase in the future.

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