AbstractSeveral herbicides were tested on Paragrass (Brachiaria mutica (Forsk.) Stapf = Panicum purpurascens Raddi) using two or more rates, and (except for Karbutilate and Diuron) one, two, and three applications at 4 weeks apart. The chemicals were applied both to tall Paragrass and short (6 to 8 inches) regrowth at the Corozal Substation in the uplands of Puerto Rico. Sprays applied to regrowth generally gave better control and for longer periods. Best control was obtained with Dalapon + TCA (trichloroacetic acid) applied twice (90 percent kill after 20 weeks). The low rate (6 pounds Dalapon plus 3.4 pounds TCA acid equiv./acre initially and one-half the rate at the repeat application) was fully as effective as the higher rate tested. Dalapon alone was nearly as effective as the Dalapon + TCA combination on both older growth and regrowth, and Asulam was highly effective when applied to regrowth. Three applications of Dalapon (6+3+3 pounds/ acre) or Asulam (3+2+2 pounds/acre) on Paragrass regrowth still gave approximately 80 percent control at 20 weeks following the initial application (12 weeks after the third application). Amitrole and Karbutilate were less effective at the rates tested. Kerb and Diuron were ineffective.
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