Effect of row spacing and herbicide programs for control of glyphosate-resistant Palmer amaranth (<i>Amaranthus palmeri</i>) in dicamba/glyphosate-resistant soybean

Abstract Glyphosate-resistant (GR) Palmer amaranth is one of the most difficult to control weeds in soybean production fields Nebraska and United States. An integrated approach required for effective management GR amaranth. Cultural practices such as narrow row spacing might augment herbicide efficacy The objectives this study were evaluate effect programs dicamba/glyphosate-resistant (DGR) soybean. Field experiments conducted a grower’s field with uniform population near Carleton, Nebraska, 2018 2019. Year-by-herbicide program-by-row interactions significant all variables; therefore, data analyzed by year. Herbicides applied PRE controlled ?95% both years 14 d after (DAPRE). Across row-spacing, followed (fb) early-POST (EPOST) provided 84% 97% compared EPOST fb late-post (LPOST) programs, excluding dicamba single sequential applications (82% 95% control). Mixing microencapsulated acetochlor POST ?93% ?96% 21 LPOST no on density. Interaction was not significant; however, biomass reduction at harvest evaluated caused injury. Due drought conditions during majority growing season, yield reduced