Chemical management of weeds in cassava crop, cultivar 'Santa Helena'.

The objective of this study was to evaluate the selectivity of cassava cultivar 'Santa Helena' and the efficiency of weed control using herbicides applied alone or tank mixed with and without sequential applications. Two experiments were carried out, both in a randomized block design with four replications. The treatments for the 1st experiment were: Hand hoeing (weed-free control); No hand hoeing (non-weeded control); sulfentrazone (500 g ha-1); sulfentrazone/[clomazone + clethodim] (500/[1125 + 120] g ha-1); sulfentrazone/mesotrione (500/240 g ha-1); S-metolachlor (1920 g ha-1); S-metolachlor/[clomazone + clethodim] (1920/[1125 + 120] g ha-1); S-metolachlor/mesotrione](1920/240 g ha-1); [sulfentrazone + S-metolachlor]/[clomazone + clethodim] ([500 + 1920]/[1125 + 120] g ha-1); [sulfentrazone + S-metolachlor]/mesotrione ([500 + 1920]/240 g ha-1). The treatments of the 2nd experiment were: Hand hoeing (weed-free control); No hand hoeing (non-weeded control); glyphosate (360 g ha-1) + hand hoeing; glyphosate + sulfentrazone (360 + 500 g ha-1); glyphosate + flumioxazin (360 + 50 g ha-1); glyphosate + clomazone (360 + 1125 g ha-1); glyphosate + S-metolachlor (360 + 1920 g ha-1); glyphosate + sulfentrazone + clomazone (360 + 400 + 900 g ha-1); glyphosate + sulfentrazone + Smetolachlor (360 + 400 + 1440 g ha-1); glyphosate + flumioxazin + clomazone (360 + 40 + 900 g ha-1); glyphosate + flumioxazin + S-metolachlor (360 + 40 + 1440 g ha-1). In the first experiment, only the treatments S-metolachlor, Smetolachlor/[ clomazone + clethodim] and S-metolachlor/mesotrione did not present efficient weed control, causing reduction in yields; the other treatments were crop selective and efficient. In the second experiment, all treatments showed excellent levels of weed control up to 65 DAA and were crop selective. It is concluded that applications of tank mixtures, sequential mixtures and the use of glyphosate mixed with pre-emergent herbicides constitute excellent alternatives of weed management strategies in 'Santa Helena' cassava. [ABSTRACT FROM AUTHOR]