Enlist™ Weed Control Systems for Palmer Amaranth (Amaranthus palmeri) Management in Texas High Plains Cotton

Weed management systems were established near Lubbock, TX in 2013, 2014, and 2015 to assess the effectiveness of premixed 2,4-D choline + glyphosate alone and in combination with glufosinate and soil-residual herbicides for Palmer amaranth control. Systems consisted of trifluralin applied preplant incorporated followed by an early POST application followed by a mid-POST application. Palmer amaranth control 21 days after the early POST application ranged from 75 to 90% for all treatments that included 2,4-D choline + glyphosate alone or in a tank-mixture in 2013. Twentyeight days after the mid-POST application, Palmer amaranth was controlled 86 to 99% for all herbicide systems with the exception of systems that included a mid-POST application of glufosinate alone. Combined across 2014 and 2015, Palmer amaranth control 21 days after the early POST application ranged from 96 to 98% for all systems that included 2,4-D choline + glyphosate, 2,4-D choline alone, or 2,4-D choline in a tank-mixture. Combined across 2014 and 2015, Palmer amaranth control 28 days after the mid-POST application ranged from 95 to 100% with the exception of the following: Trifluralin preplant incorporated followed by glufosinate with or without acetochlor applied early POST followed by glufosinate mid-POST and trifluralin preplant incorporated followed by glyphosate early POST followed by glyphosate mid-POST. Overall, numerous effective systems were identified; however, systems containing 2,4-D choline + glyphosate or 2,4-D choline early POST and/or mid-POST were among the most effective. Glyphosate or glufosinate only systems or systems that relied on glufosinate alone at the mid-POST timing were inconsistent and often performed poorly. Nomenclature: 2,4-D choline; glyphosate; glufosinate; Palmer amaranth, Amaranthus palmeri S. Wats.; cotton, Gossypium hirsutum L.