This study aimed to assess the tolerance of cultivars of sugarcane to herbicides applied in post-emergence initial of ratoon. The experiment was carried in Ribeirão Preto, SP, Brazil, in the agricultural year 2007/2008. The experimental design was the randomized blocks, in split-plots, 36 treatments and four replications. It was used the cultivars IACSP94-2094, IACSP94-2101, IACSP93-3046, IACSP94-4004, RB72454 and IAC86-2480 in plots and herbicides, were made by mixture ready to diuron (1170 g ha-1) + hexazinone (330 g ha -1); diuron (1865 g ha-1) + hexazinone (234 g ha-1); metribuzin; tebuthiuron; amicarbazone and a control in the sub-plots. The intoxication symptoms of visual, relative content of chlorophyll and photochemical efficiency of PS II, height, stand, technological quality of sugarcane and production the culms. It was concluded the cultivars IACSP94-2094, IACSP94-2101, IACSP93-3046, IACSP94-4004, RB72454 and IAC86-2480 were not affected by herbicides, only showed differences inherent in the genetics. In all cultivars, there was only mild intoxication symptoms of visual at the initial stage of development and there was not any damage to the content of chlorophyll, measured by relative content chlorophyll. The photosynthetic system showed little damage in the initial phase, when measured by the photochemical efficiency of PS II (Fv/Fm), but that was not enough to constrain the height, stand, production and technology quality of different cultivars of sugarcane studied.
Saccharum spp.; selectivity; intoxication symptoms; phytotoxicity
