This work evaluated the effects of residual herbicides, applied in crop pre-emergence, on the reduction of Alexander grass (Urochloa plantaginea) infestation in the common bean. Two field experiments were conducted at Eldorado do Sul, RS/Brazil: one using the bean cultivar UFT-06 (Red group), and the other using IPR Graúna (Black group). The experiments were arranged in a randomized block design, with four replicates, and the treatments consisted of four herbicides, at two rates (kg i.a. ha-1), as follows: pendimethalin and trifluralin (1.2 and 1.4), and s metolachlor and dimethenamid (1.4 and 1.6). Control and shoot mass of Alexander grass were assessed at 20 and 40 days after crop emergence, which includes the critical period of weed interference. All residual herbicides reduced Alexander grass infestation during this period, and the best weed control was obtained with trifluralin herbicide in both experiments. To successfully reduce Alexander grass infestation with residual herbicides, weed management actions must be taken during common bean post-emergence.
bean; weeds; chemical control; pre-emergence
