Application of Herbicides on Rangelands with a Carpeted Roller: Timing of Treatment in Dense Stands of Honey Mesquite

Abstract

Several herbicides were evaluated for control of honey mesquite (Prosopis glandulosa Torr.) when applied with a tractor-mounted carpeted roller. Experiments were placed in stands with relatively high honey mesquite densities (2,850 to 4,930 plants/ha). An ester of 2,4,5-T was ineffective at concentrations ranging from 3 to 240 g/L when applied monthly from April through September. Equal-ratio mixtures of 2,4,5-T and picloram provided up to 80% mortality (root-kill) when applied at a total concentration of 24 g/L in June, but did not control honey mesquite if applied in September. Mortality obtained with picloram applied alone in June as a 12 g/L solution varied with year and location from 42 to 61%. Picloram provided 61 to 91% mortality at a concentration of 60 g/L when applied in June, and up to 99% mortality when applied as a 120 g/L solution. Picloram was highly effective when applied in July and August in a year of favorable growing conditions, providing 94 and 96% mortality as 60 g/L solutions, respectively. Mortality was reduced to a maximum of 79% when picloram was applied from April through September in a drought year. Clopyralid and a 1:1 mixture of picloram and clopyralid were usually equal or superior to picloram in effectiveness.