Selectivity and efficiency of pre-emergent herbicides on cassava crop

The chemical control of weeds stands out as an important tool for obtaining high yields in cassava crops. This study aimed at evaluating the selectivity and efficiency of pre-emergent herbicides on cassava ('Cascuda' cultivar) crop. The experimental design was randomized blocks, with ten treatments and four replications. The treatments consisted of clomazone (900 g ha-1 and 1,080 g ha-1), flumioxazin (60 g ha-1), sulfentrazone (600 g ha-1), S-metolachlor (1,920 g ha-1), clomazone + flumioxazin (900 + 50 g ha-1), clomazone + sulfentrazone (900 + 500 g ha-1) and clomazone + S-metolachlor (900 + 1,440 g ha-1), as well as a weeded and a non-weeded control. The weed community was composed by 9 families and 12 species, with the Asteraceae and Poaceae families presenting the highest number of species. The pre-emergent herbicides were selective for 'Cascuda' cultivar cassava plants. The herbicides were effective in controlling weeds, with flumioxazin (60 g ha-1), sulfentrazone (600 g ha-1), S-metolachlor (1,920 g ha-1) and the mixtures of clomazone + flumioxazin (900 + 50 g ha-1), clomazone + sulfentrazone (900 + 500 g ha-1) and clomazone + S-metolachlor (900 + 1,440 g ha-1) presenting the highest residual effect.