Selective control of grass weeds in soyabeans with some recently developed post-emergence herbicides

Abstract Four trials in soyabeans were conducted in Parana, Brazil, to evaluate the activity and selectivity of the post‐emergence herbicides fluazifop‐butyl, sethoxydim, diclofop‐methyl, CGA 82725, Ro 13–8895, and the mixed formulation mefluidide + bentazone. Diclofop‐methyl and, to a greater extent, mefluidide + bentazone, caused necrotic spots and stains on the trifoliated leaves of soyabeans; the mixture had a dwarfing effect on the crop. The remaining herbicides caused a slight delay in crop growth, but the plants recovered rapidly. CGA 82725, Ro 13–8895 and fluazifop‐butyl, all at 0.25 kg a.i./ha, and sethoxydim at 0.18 kg a.i./ha, gave good control of Brachiaria plantaginea (Link) Hitchc, Digitaria sanguinalis (L.) Scop, and Cenchrus echinatus L., when applied up to the 3–4 tiller stage. At later stages, efficacy was lower but acceptable. These herbicides acted slowly and took 20 days to take complete effect. CGA 82725, Ro 13–8895 and fluazifop‐butyl left some residual effect, preventing later rein...