Manejo de Conyza bonariensis com glyphosate + 2,4-D e amônio-glufosinate em função do estádio de desenvolvimento

Abstract

Knowing the stage where the weed is more susceptible to chemical control is a fundamental part of weeds integrated management. In the specific case of C. bonariensis that is a weed with difficult control, this knowledge has a direct influence on herbicides efficiency. Thus the aim of the present study was to evaluate the effectiveness of glyphosate + 2,4-D and glufosinate herbicides in controlling C. bonariensis sprayed at different stages of development. Treatments were arranged in a 2x5 factorial scheme, where the first factor was represented by glyphosate + 2,4-D (960 + 496 g ha-1) and glufosinate (400 g ha-1) and second one for different development stages of C. bonariensis plants (cotyledon or 0, 7, 14, 21 and 28 cm height). For each development stage of this specie was used a check for evaluating the efficiency of these herbicides and dry mass comparison. The development stage of C. bonariensis plants at application time affects significantly the efficiency of glyphosate + 2,4-D and glufosinate herbicides. Excellent controls for this species occurred when glyphosate + 2,4-D and glufosinate applications were performed on plants taller than 6 cm. Satisfactory control of C. bonariensis was obtained when plants showed maximum height of 10 and 11 cm at application time of glyphosate+2,4-D and glufosinate herbicides, respectively.