Glufosinate plus Dicamba for Rescue Palmer Amaranth Control in XtendFlex^TMCotton

Abstract

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. Glufosinate-ammonium at 590 g ai ha−1plus dicamba diglycolamine salt at 560 g ae ha−1POST-1 followed by glufosinate plus dicamba POST-2 was more effective than glufosinate at 880 g ha−1POST-1 followed by glufosinate at 590 g ha−1POST-2 or dicamba alone applied twice. Following a directed layby application of glyphosate, diuron, andS-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.

Sequential Applications of Synthetic Auxins and Glufosinate for Escaped Palmer Amaranth Control

“…Regrowth of Palmer amaranth is often a major concern associated with glufosinate applications as glufosinate does not prevent weed regrowth [26,27]. All treatments in this study resulted in similar and significantly lower leaf biomass and area 14 DAIT as compared to the nontreated control (Table 7).…”

“…Under such circumstances, producers often seek out rescue herbicide programs to control large escapes and prevent crop loss [19,[21][22][23]. Combinations of glufosinate and synthetic auxins have been shown to be more effective on control of larger weeds than when applied alone [19,21,[24][25][26]. Merchant et al [24] observed up to 22%, 17%, and 11% greater Palmer amaranth control 20 d after application when glufosinate at 431 g ai ha −1 was tank mixed with 2,4-DB, 2,4-D, or dicamba than when these three herbicides applied alone at 1120, 1064, and 1120 g ai ha −1 , respectively.…”

Functional PPO2 mutations: co‐occurrence in one plant or the same ppo2 allele of herbicide‐resistant Amaranthus palmeri in the US mid‐south

“…Among all weeds, Palmer amaranth had the greatest shift in importance in the Mid‐south from 1994/1995 to 2008/2009 advancing from 25th to 7th 18 . The rapid spread of Palmer amaranth populations resistant to glyphosate triggered extensive research for, and adoption of, new management strategies 19,20 . In Georgia, a 10‐fold increase in fomesafen and flumioxazin usage was reported after the spread of GR Palmer amaranth 21 .…”

Hapten Synthesis, Antibody Development, and a Highly Sensitive Indirect Competitive Chemiluminescent Enzyme Immunoassay for Detection of Dicamba

“…The release of dicambaresistant genetically modified plants (soybean, cotton) by Monsanto is another important factor that promoted an increase worldwide use of dicamba. [3][4][5] However, dicamba from the old formulations was shown to drift after application. It was reported to vaporize from the treated fields and spread to neighboring non-resistant crops.…”