Weed control in established alfalfa (Medicago sativa) with postemergence herbicides.
Field experiments were conducted during 1998, 1999, and 2000 in Santa Fe, Argentina, to evaluate chlorimuron, clethodim, flumetsulam, 2,4-DB, glyphosate, and haloxyfop for control of broadleaf and grass weeds in established lucerne. Herbicides were applied to lucerne, 6 to 10 cm in height, after first or second cuttings. Clethodim and haloxyfop were highly effective against bermudagrass (Cynodon dactylon), barnyardgrass (Echinochloa crus-galli), and knotroot foxtail (Setaria geniculata [S. parviflora]), and lucerne yields were increased. 2,4-DB was effective against Scotch thistle (Onopordum acanthium), swinecress (Coronopus didymus), turnipweed (Rapistrum rugosum), and birdsrape mustard (Brassica rapa [B. campestris]), but no effects were observed on lucerne yields. Chlorimuron, flumetsulam, and glyphosate were effective against burning nettle (Urtica urens), common chickweed (Stellaria media), common lambsquarters (Chenopodium album), spiny cocklebur (Xanthium spinosum), and Persian speedwell (Veronica persica), but they injured lucerne and decreased yields.