Sequential applications of herbicides in the management of weeds at an advanced stage of development

Weeds such as Spermacocea verticillata (button broom) and Commelina benghalensis (benghal dayflower) are being selected in areas with intensive use of glyphosate due to the tolerance of these species to this herbicide. The ideal is the initial control of weeds; however, this is not always done, and at an advanced phenological stage, the effectiveness of the control may be reduced. The objective of this study was to evaluate the control of adult stage of S. verticillata and C. benghalensis plants using herbicides alone or with glyphosate, followed or not by sequential application of diquat and glufosinate ammonium. The experiment was performed individually for each species in a completely randomized design, with five replicates, in a 9 x 4 factorial scheme consisted of 9 treatments, with applications of chlorimuron - ethyl - 20 g ha -1, s -metolachlor - 960 g ha -1, carfentrazone -ethyl - 20 g ha -1, 2,4 -D -1000 g ha -1, chlorimuron -ethyl + glyphosate - 20 + 1,440 g ha -1, s -metolachlor + glyphosate - 960 + 1,440 g ha -1, carfentrazone -ethyl + glyphosate - 20 + 1,440 g ha -1, 2,4 -D + glyphosate - 1000 + 1,440 g ha -1 and without initial herbicide on adult plants and 4 sequential applications 15 days after the first application with diquat -200 g ha -1,glufosinate ammonium - 200 g ha -1, ammonium glufosinate - 400 g ha -1 and without sequential herbicide, in adult plants of both species. For C. benghalensis, the carfentrazone-ethyl, carfentrazone-ethyl + glyphosate and 2,4-D + glyphosate treatments were effective, regardless of sequential application. The treatments s-metolachor and 2,4-D with glufosinate ammonium were not effective in controlling this species. Conversely, S. verticillata without sequential application was controlled only by chlorimuron-ethyl + glyphosate. Carfentrazone-ethyl was the least effective treatment in sequential applications for the control of this species. It is concluded that there are options for chemical control of the species S. verticillata and C. benghalensis in advanced development stages in single or sequential applications, and the species differ in relation to the effectiveness of the herbicides.