Protecting the world's rice crops.
The global problem of weed infestation of rice crops is discussed with particular reference to weed competition and chemical weed control. Out of 350 species infesting rice fields Echinochloa glabrescens, E. crus-galli, E. colonum, Leptochloa chinensis, Paspalum paspalodes and wild rice are the most common grass weeds. Fimbristylis miliacea, Cyperus spp. and Scirpus maritimus are important weed sedges. Sphenoclea zeylanica, Monochoria vaginalis, Marsilea minuta, Ludwigia octovalvis, Commelina benghalensis, Ammania baccifera, Eclipta alba and Ipomoea aquatica represent the main broadleaved weeds. Popular herbicides are MCPA and 2,4-D which are applied at 0.5-1.0 kg/ha, although crop injury may occur if N fertilizer is applied 10-15 days before or after the phenoxy herbicides. Butachlor possesses strong selectivity against Echinochloa spp. and controls most broadleaved weeds, annual grasses and sedges. Other herbicides used to control weeds in rice crops include thiobencarb, oxyfluorfen, pendimethalin, bentazone and molinate.