Chemical weed control in soybean in Brazil using new herbicides and mixtures.
The newly-introduced herbicides carfentrazone and carfentrazone-ester were tested for weed control in soyabeans in São Paulo State, Brazil in 1996. The herbicides were compared with standard treatments (chlorimuron-ethyl + lactofen and chlorimuron-ethyl + imazethapyr) when sprayed alone and in mixtures with chlorimuron-ethyl. Phytotoxicity assessments on soyabeans were carried out 15, 30, 45 and 65 days after treatment. As a result of this research, carfentrazone (20 g a.i./ha) and carfentrazone-ester (10 or 12.5 g a.i./ha) are recommended as safe when sprayed alone or when mixed with chlorimuron-ethyl, as there were no phytotoxic effects on the vegetative growth of soyabeans. The control of major broadleaf weeds in soyabeans (Commelina benghalensis, Ipomoea grandifolia and Acanthospermum hispidum) was satisfactory (80.7-90.0, 92.5-99.5 and 90.0-100.0% control, respectively, at 15 days after treatment) and the spectrum of controlled weeds was enhanced when mixed with chlorimuron-ethyl, showing a good alternative for herbicide resistance management.