Die chemiese beheer van Pachystigma pygmaeum [Schltr.] Robyns

Abstract

A comparative investigation of the influence of the herbi­ cides Tordon 22K, Tordon 22K + 1.0 percent DMSO,-Tordon 101, 2, 4-D and 2, 4, 5-T on Pachystigrna pygmaeurn (Schltr.) Robyns was carried out in order to establish which of these could be used in the control of this poisonous plant. It soon became evident that 2, 4-D and 2, 4, 5-T had a negligible effect on P. pygmaeurn. A single spraying with the various Tordon formulations was carried out at each of two localities. Two years after the first spraying with Tordon 22K, Tordon 22K + 1.0 percent DMSO and Tordon 101 as a surface spray, at 0.560 kg, 1.121 kg and 2.242 kg a.e. picloram per hectare, there was a reduction in the number of aerial leaf bearing twigs of P. pygmaeum at all concentrations of all herbicides. A concentration of 2.242 kg a.e. picloram per hectare gave the most effective control and all three Tordon formulations were equally effective. One year after the second spraying with the same three Tordon fromulations, but at five concentrations viz. 0.560 kg, 1.121 kg, 2.242 kg, 4.483 kg and 6.725 kg a.e. picloram per hectare there was. a reduction in the number of aerial leaf bearing twigs of P. pygmaeurn at all concentrations of all the Tordon for­mulations. Tordon 101 at 6.725 kg a.e. picloram per hectare re­sulted in the most effective control of P. pygmaeum.