Tolerance of sugarcane cultivars to chemical eradication Tolerancia de cultivares de cana-de-a úcar à erradica o química

Knowledge of the minimum rate of glyphosate required to eradicate sugarcane ratoons can reduce the amount of herbicide used. To confirm this hypothesis, this study aimed to investigate the tolerance of different sugarcane cultivars to chemical eradication, at different glyphosate rates. The experiment was conducted in a randomized block design in a split-plot scheme, with four replications. The sugarcane cultivars (IACSP94-2094, IACSP94-2101, IACSP93-3046, IACSP94 4004, IAC86-2480, and RB72454) were allocated in plots and the glyphosate rates (0, 1,440, 2,160, 2,880, 3,600, and 4,320 g ha-1), in the sub plots. The traits evaluated were signs of poisoning symptoms; total chlorophyll content, plant height, percentage of dead tillers, and dry weight of the plants. At 45 days after application (DAA), the glyphosate rate of 1,440 g a.e. ha-1 eradicated the cultivars IACSP94-2094 and IACSP94-2101, as well as RB72454 with application of 2,160 g a.e. ha 1. Application of glyphosate 2,880 g a.e. ha-1 eradicated both IACSP93-3046 and IAC86-2480 and glyphosate 3,600 g a.e. ha-1 eradicated IACSP94-4004. The most tolerant cultivar was IACSP94 4004, eradicated at the rate of 3,600 g. a.e. ha-1. This confirms the hypothesis that knowing the cultivar's tolerance leads, in practice, to a smaller amount of herbicide applied to the environment, which also reduces production costs. O conhecimento da dose mínima de glyphosate utilizada na erradica o das soqueiras de cana-de-a úcar traz como benefício a redu o na quantidade do herbicida. Para comprovar essa hipótese, o objetivo desta pesquisa foi estudar a tolerancia das soqueiras de cultivares de cana-de-a úcar à erradica o química, a partir de diferentes doses de glyphosate. O experimento foi instalado em delineamento de blocos casualizados, arranjado em esquema de parcelas subdivididas com quatro repeti es. Nas parcelas foram alocadas os cultivares de cana-de-a úcar RB72454, IACSP86-2480, IACSP93-3046, IACSP94-2094, IACSP94-2101 e IACSP94-4004 e, nas subparcelas, as doses de glyphosate: 0; 1.440; 2.160; 2.880; 3.600 e 4.320 g e.a. ha-1. As características avaliadas foram sintomas visuais de intoxica o, teor de clorofila total, altura de plantas, porcentagem de perfilhos mortos e massa seca de plantas. Aos 45 dias após a aplica o (DAA), a partir de 1.440 g e.a. ha 1 do glyphosate, os cultivares IACSP94-2094 e IACSP94-2101 foram erradicadas, bem como a RB72454 com aplica o de 2.160 g e.a. ha-1. Na utiliza o do glyphosate a 2.880 g e.a. ha-1 foram erradicadas a IACSP93-3046 e IAC86-2480. O cultivar de maior toleranci