Integrating Cover Crops and POST Herbicides for Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Control in Corn

Abstract

Field experiments were conducted in 2013 and 2014 in Jackson, TN, to evaluate the efficacy of integrating cover crops and POST herbicides in corn to control glyphosate-resistant (GR) Palmer amaranth. Crimson clover and hairy vetch were planted in the fall and accumulated greater than 1,600 kg ha−1aboveground biomass by time of termination. Crimson clover and hairy vetch provided 62% and 58% Palmer amaranth control 14 d before application, respectively. POST herbicide treatments of glyphosate +S-metolachlor + mesotrione + atrazine, thiencarbazone-methyl + tembotrione + atrazine, and glyphosate + atrazine were applied when Palmer amaranth reached 15 cm tall. The herbicide treatments provided greater than 95% control of Palmer amaranth 28 d after application. In addition to Palmer amaranth suppression, corn was taller at V5 and V7 following a hairy vetch cover crop. Hairy vetch and crimson clover residues provided early season weed suppression because of biomass accumulation. Palmer amaranth in the nontreated control plots reached 15 cm 4 and 3 d ahead of the cover-treated plots in 2013 and 2014, respectively. This could potentially increase POST herbicide-application flexibility for producers. Results of this trial also suggest that cover crops alone are not a means of season-long control of GR Palmer amaranth. From a herbicide resistance-management perspective, the integration of cover crops with herbicide mixtures that incorporate multiple sites of action should aid in mitigating the further selection of herbicide resistance in Palmer amaranth.