APLICAÇÃO SEQUENCIAL DE HERBICIDAS DESSECANTES NO MANEJO DO CAPIM-AMARGOSO (Digitaria insularis (L.) Fedde)

Abstract

Sourgrass (Digitaria insularis) stands out because of its high competitive potential, its distribution in practically all the producing regions of Brazil and the increase in the population of glyphosate-resistant biotypes and, more recently, resistance to some herbicide-inhibiting herbicides ACCase (fenoxaprop and haloxyfop). This work aims to evaluate the control of sourgrass (D. insularis) through the positioning of contact herbicides associated to the sequential application of Glyphosate in combination with Clethodin at different intervals in pre-sowing. The experiment was conducted in a randomized complete block, with four replicates in a 4x4 factorial scheme, where four strategies were evaluated with contact herbicides (600 g ia ha-1 ammonium Glufosinate, Paraquat 600 g ia ha-1 and Saflufenacil, 49 g ia ha-1) and a control that did not receive the first application. The second factor was the time of application of the treatment with Glyphosate herbicide combined with Clethodin aiming desiccation of the sourgrass in pre-sowing. At 7, 14, 21 and 28 days, the height - AL (m) and the EHC (%) Contact Herbicide Efficiency were evaluated, prior to the second application. After the second application, at 7, 14, 21 and 28 days, the control of sourgrass was evaluated through phytotoxication notes (using a scale from 0 to 100%), and the Percentage of Regrowth - PR (%) at 14, 21 and 28 days after application. The isolated treatments with contact herbicides, as well as the application of Glyphosate + Clethodin alone in the pre-sowing desiccation were not efficient in the control of perennial D. insularis plants. The highest control means involve the first application with Paraquat, 95,5% of control, and with ammonium Glufosinate, 91,7% of control. The interval between sequential applications that best favors the control of sourgrass plants in the reproductive phase is 14 days. At 28 days after application of Glyphosate + Clethodin, the effect of the treatments reduces and regrowth in all management proposals evaluated, except for treatment with ammonium Glufosinate in the first application and 21 days interval for the second application.