Control of black wattle (Acacia mearnsii De Wild.) seedlings with Garlon herbicide applied by backpack mistblower

Abstract

Black wattle (Acacia mearnsii De Wild) has great economic value for South Africa, but also poses a tremendous threat to our natural ecosystems once it “escapes” from plantations into the surrounding grassland and watercourses, often forming dense, impenetrable thickets that displace the natural vegetation and hamper water flow. The herbicide Garlon 4 (triclopyr butoxy ethyl ester 480 g/í EC) is registered in South Africa for foliar treatment of black wattle by knapsack or tractor mounted boom sprayer only. These are the most commonly used methods for controlling massive seedling regeneration after initial clearing or fire. The aim of this study was to evaluate the effectiveness of a backpack mistblower and different mixtures of Garlon 4 as an alternative method for treating extensive stands of black wattle seedlings. The currently registered concentrations for knapsack application of 0.25% – 0.75% in water, and a reduced concentration of 0.125% were all found to provide commercially acceptable levels of control. Backpack mistblowers have many advantages over knapsack sprayers for treating large areas and the good results obtained with very low concentrations of Garlon 4 implies improved cost-benefit, with less negative impact on the environment.