The study was conductedin a representative native pasture area in the transition between the Serrado Sudeste and Depressão Central of RS. The main undesirable specieswere represented by: carqueja (Baccharis trimera (Less.) DC.), caraguatá(Eryngium horridum (Spreng.) Less.) and alecrim (Vernonia nudifloraLess). It was evaluated the initial effect (until 60 days after application)of two methods of controlling undesirable plants on forage production, vegetationdynamics, and control efficiency: T1 - without control (control,SC), T2 - mechanical control (mechanic control, CM) and T3- chemical control (commercial herbicide composed by Picloram (64 g/L) + 2.4-D(240 g/L), in the dosage of 5 L commercial product/ha, CQ). The treatments wereorganized in a complete block design, with four replications. There were nodifferences among treatments for the green dry matter of grasses and total DM.The forage legume biomass differed among treatments, with values of 587.9, 472.0and 0 kg/ha of DM in the CM, CQ and SQ, respectively. The control efficiencyof undesirable species in this study was 76.2% for CQ and 27.9% for CM whencompared to SC. The species control efficiency, in terms of frequency of pasturecomponents, showed that the CM treatment was not efficient at 60 days aftertreatment application in the control of Vernonia nudiflora (Alecrim)in the second touch (-27.7%) and Eryngium horridum (Caraguatá)in the first touch (-30.0%).
