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

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%.     

The effect of ringbarking Brachystegia spiciformis Benth., Julbernardia globiflora (Benth.) Troupin and Terminaliasericea Burch. ex DC. trees at different heights with or without the addition of a pidoram/2,4‐D mixture

Trees were ringbarked at three different heights relative to ground level (1 000 mm above the ground, at ground level and 100 mm below ground level). In a separate trial, arboricide was applied at four different rates to the lower lip of the ringbarked trees either 1 000 mm above the ground or at ground level. Ringbarking without the arboricide was most effective when carried out in February and at a height of 1 000 mm above the ground. Application of a picloram/2,4‐D mixture to the lower lip of ringbarked trees in January or April resulted in higher kill rates than applications made in June or October. Using this method, somewhat less picloram was necessary than was required to effect the same kill rate to these tree species by applying the arboricide to cuts in their stem bases. In both trials, the kill rate was positively related to the amount of coppice removed.