Successive applications of glyphosate in Brazil have selected weed species hard to kill by usually recommended doses. However tank mixtures with low rates of non-systemic herbicides increase the efficacy of glyphosate. The efficacy on five weed species of glyphosate alone and in mixture with carfentrazone-ethyl (5 ml of carfentrazone/litre of glyphosate), with rainfall simulation after application was studied in the greenhouse. Treatments were also compared under field conditions in a no-till system,with herbicides applied pre-planting, to pasture. The treatments were: glyphosate (formulation 480 g/litre) with carfentrazone at 720 + 2.0; 720 + 3.0; 720 + 4.0; 960 + 2.0; 960 + 3.0 and 960 + 4.0 and glyphosate (formulation 648 g/litre) at 712.8 and 972 g/ha, plus a check plot without herbicide application. The efficacy of glyphosate was enhanced by the addition of 2.0 g/ha of carfentrazone (corresponding to 5 ml of commercial product/litre of glyphosate), being equivalent to the activity of similarrates of the formulation of 648 g/litre. The mixture increased the spectrum and efficiency of control of broad-leaved species, particularly Commelina benghalensis, and showed reduced susceptibility to rainfall after application.
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