Glufosinate plus Dicamba for Rescue Palmer Amaranth Control in XtendFlex™ Cotton

• Published in: Weed technology Vol. 31; no. 5; pp. 666 - 674
• Main Authors: Vann, Rachel A., York, Alan C., Cahoon, Charles W., Buck, Trace B., Askew, Matthew C., Seagroves, Richard W.
• Format: Journal Article
• Language: English
• Published: Lawrence Weed Science Society of America 01.09.2017; Cambridge University Press
• Subjects: Agriculture; Amaranth; Amaranthus; Amaranthus palmeri; Ammonium; Cotton; Diuron; Glufosinate; Glyphosate; Gossypium hirsutum; Herbicide resistance; Herbicides; Lint; Metolachlor; WEED MANAGEMENT-MAJOR CROPS; Weeds; United States > US; Georgia
• ISSN: 0890-037X; 1550-2740
• DOI: 10.1017/wet.2017.68

Cotton growers commonly use glufosinate-based programs to control glyphosate-resistant Palmer amaranth. Palmer amaranth must be small (≤7.5 cm) for consistent control by glufosinate, and growers often miss the optimum application timing. XtendFlex™ cotton may provide growers a tool to control larger Palmer amaranth. Glufosinate, dicamba, and glufosinate plus dicamba were compared for Palmer amaranth control in a rescue situation. Herbicides were applied to 16- to 23-cm weeds (POST-1) followed by a second application (POST-2) 12 d later. Glufosinateammonium at 590 g ai ha−1 plus dicamba diglycolamine salt at 560 g ae ha−1 POST-1 followed by glufosinate plus dicamba POST-2 was more effective than glufosinate at 880 g ha−1 POST-1 followed by glufosinate at 590 g ha−1 POST-2 or dicamba alone applied twice. Following a directed layby application of glyphosate, diuron, and S-metolachlor 14 d after POST-2, Palmer amaranth was controlled 99% by any system containing dicamba or glufosinate plus dicamba POST-1 followed by dicamba, glufosinate, or glufosinate plus dicamba POST-2 compared with 87% to 91% control by glufosinate alone applied twice. Cotton height and number of main stem nodes at layby were reduced in systems with dicamba only POST-1 followed by dicamba or glufosinate plus dicamba POST-2, presumably due to competition from the slowly dying Palmer amaranth with dicamba only POST-1. These treatments also delayed cotton maturity and reduced lint yield compared with systems containing glufosinate plus dicamba at POST-1.