Chemical control of Cyperus rotundus on sugar-cane crop

摘要

This work evaluated the effect of doses (1.0, 1.5, and 2.0 kg ha-1) and periods of spraying (pre and post-emergence) of ametryn + trifloxysulfuron-sodium commercial mixture to Cyperus rotundus control, in sugar-cane crop, compared to 1.0 kg ha-1 pre + 1.0 kg ha-1 postemergence of the same mixture, 0.90 kg ha-1 of sulfentrazone in pre-emergence, besides the treatments with and without weeding. A greater effect in dry mass reduction of C. rotundus was provided by the treatments 1.0 kg ha-1 pre + 1.0 kg ha-1 post and 2.0 kg ha-1 of ametryn + trifloxysulfuron-sodium post-emergence commercial mixture, respectively, as the average percentage of visual control verified in those treatments was 86.8%. About the effects on shoot number of C. rotundus, except for the treatment (2.0 kg ha-1) in post-emergence, the pre emergence treatments of the mixture were more efficient in reducing it. Yet, only sulfentrazone or the smallest dose 1.0 kg ha-1 of ametryn + trifloxysulfuron-sodium in pre-emergence showed low efficiency on C. rotundus reduction, with average visual control lowe than 40%. Although, in pre-emergence applications, the estimated dose of 1.25 kg ha-1 did not differ from 2.0 kg ha-1 of the commercial mixture, in reducing dry mass of the aerial part of C. rotundus, the application of 2.0 kg ha-1 post-emergence presented significant effect, compared to the other doses, with remaining action control of this species. None of the treatments evaluated affected sugar-cane, variety RB 72454.