Glyphosate-resistant horseweed control in glyphosate/glufosinate/2,4-D-resistant soybean with one- and two-pass herbicide programs

Abstract Glyphosate-resistant (GR) biotypes of horseweed were first confirmed in southern Ontario 2010 and have spread across Ontario. A total four field experiments conducted between 2021 2022 to determine GR control with one- two-pass herbicide programs glyphosate/glufosinate/2,4-D-resistant (GG2R) soybean. 2,4-D choline/glyphosate DMA, halauxifen-methyl, saflufenacil applied preplant (PP) controlled by 59%, 72%, 78% 8 wk after postemergence (POST) application (WAA-POST); there was no improvement when DMA added saflufenacil; contrast, improved DMA. Glufosinate POST glyphosate-resistant 71% 86%, respectively, WAA-POST. Two-pass a PP followed provided greater than or alone. following halauxifen-methyl 29% 38% 24%, respectively at The 20% WAA-POST; glufosinate either + PP. When used program, 2% 3% glufosinate.