Weed control in cowpea (Vigna unguiculata) with sethoxydim and Galex.
Field trials were conducted to compare the use of pre- and post-em. applications of 1-4 kg/ha Galex (metobromuron + metolachlor) and 0.3-1.5 kg sethoxydim, resp., with manual weeding treatments at 15 and 40 d after planting (DAP) for the control of weeds in cowpeas on loamy sand. All herbicide treatments reduced weed populations at 47 DAP from 186/m2 in unweeded controls to <77 but only 4.0 kg Galex was as effective as manual weeding (21 and 22 weeds/m2, resp.). Weed biomass at harvest was also reduced from 284.0 g/m2 to <180 g by 1-4 kg Galex and 1.5 kg sethoxydim, but lower concn of sethoxydim were ineffective, and no herbicide compared favourably with the 24.7 g weeds resulting from hand weeding. Galex controlled most annual broadleaved and grass weeds (e.g. Achyranthes aspera, Borreria ocymoides, Digitaria horizontalis, Echinochloa colonum and Tridax procumbens) but was ineffective against Commelina benghalensis, and Rottboellia cochinchinensis. Conversely, effective control of the latter and some grassy weeds was achieved with sethoxydim, although it failed to control most broadleaved weeds. Cowpea grain yields were increased from 0.55 t/ha to 0.96 t by hand weeding and 0.71-0.88 t by the herbicides, the most beneficial of which were 2-3 kg Galex (the higher concn was marginally phytotoxic) and 1.5 kg sethoxydim (0.84-0.88 t).