J.C. SCANLAN

Queensland Department of Primary Industries P.O. Box 689, Rockhampton, Queensland 4700.

Abstract

Triclopyr ester, hexazinone, carbamoylphosphoniate, glyphosate and two formulations of 3,6-dichloropicolinic acid were compared with 2,4,5-T ester for brigalow (Acacia harpophylla) regrowth control.
Triclopyr ester (at 1 g L^-1 in 1000 L ha^-1) gave good control of regrowth less than 12 months old and was superior to 2,4,5-T ester on four year old regrowth (at 20 g L^-1 in 50 L ha^-1). Water was an efficient carrier for misting of triclopyr ester but when 2,4,5-T ester, was used, distillate was a more efficient carrier than water.
Hexazinone gave high mortality of brigalow regrowth when applied as an overall spray (2 g L^-1 in 1000 L ha^-1) or as a spot application of the liquid-formulation (1 g plant^-1). Clay pellets impregnated with hexazinone were ineffective on brigalow less than 12 months old. Reduced grass cover was evident after two growing seasons where 8 kg ha^-1 of hexazinone had been applied as a ground application or as a spray.
Glyphosate at 1.8 to 7.2 g L^-1 and carbamoylphosphonate at 1.2 to 4.8 g L^-1 were ineffective as overall sprays when applied at 1000 L ha^-1 in January–February to brigalow suckers less than 12 months old. Ester and amine formulations of 3,6 dichloropicolinic acid were effective at 4 g L^-1 in 1000 L ha^-1 on the same regrowth.
The possible roles of triclopyr ester and hexazinone in future brigalow regrowth control are discussed.