Cotton growers commonly use glufosinate-based programs to control glyphosate-resistant Palmer amaranth. Palmer amaranth must be small (amp;= 7.5 cm) for consistent control by glufosinate, and growers often miss the optimum application timing. XtendFlex (TM) 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. Glufosinate-ammonium 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.
展开▼
