The application of various picloram formulations to cut stumps of Brachystegia spiciformis Benth., Julbernardia globiflora (Benth.) Troupin, Terminalia sericea Burch. ex DC. and Acacia karroo Hayne trees

Abstract

Trees were felled 150 mm above ground level and various mixtures of picloram with 2,4‐D araine, 2,4,5‐T amine in water solution or 2,4,5‐T ester in diesel oil were applied to the freshly‐cut surfaces. Mixtures of picloram/2,4‐D amine and picloram/2,4,5‐T amine, both water soluble, gave the highest kill rates when applied to trees in the growing season (October and May). The oil emulsifiable picloram/2,4,5‐T ester formulation tended to be effective throughout the year and high kill rates were frequently obtained with applications made in June or July. Application rates of picloram/2,4‐D amine or picloram/2,4,5‐T amine (expressed as g a.e. picloram per mm girth) required to kill 80% of the trees were 0,012–0,016 for A. karroo; 0,016–0,037 for T. sericea and 0,037 for J. globiflora. Few of the treatments applied to B. spiciformis trees resulted in kill rates of more than 65%.