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Published online by Cambridge University Press: 21 November 2025
Recent reports of glyphosate-resistant (GR) waterhemp pose serious concerns among New York (NY) producers. Field experiments were conducted in 2019 and 2020 near Waterloo, NY, to evaluate the effectiveness of preemergence (PRE), postemergence (POST), PRE followed by (fb) POST, and PRE fb row cultivation (RC) for GR waterhemp control in dicamba-resistant (DR) soybean. In 2019, all two-pass programs significantly reduced GR waterhemp densities (2 to 13 plants m-2) as compared to nontreated (160 plant m-2) at 8 weeks after PRE (WAPRE)/2 weeks after POST (WAPOST), shoot dry biomass (85 to 99% of nontreated) and resulted in greater soybean grain yields (2,659 to 2,936 kg ha-1). In addition, flumioxazin, acetochlor, chlorimuron + flumioxazin + metribuzin, acetochlor + fomesafen + metribuzin, carfentrazone + sulfentrazone + metribuzin and S-metolachlor + sulfentrazone + metribuzin applied PRE resulted in significant reductions in GR waterhemp density (3 to 19 plants m-2) and shoot dry biomass (60 to 98% of nontreated). In 2020, most PRE (except cloransulam), POST only or PRE fb POST strategies reduced densities of GR waterhemp (1 to 46 plants m-2) as compared to nontreated (104 plants m-2) at 8 WAPRE/ 2WAPOST and shoot dry biomass (66 to 99% of nontreated). All two-pass strategies as well as metribuzin, acetochlor + fomesafen + metribuzin, carfentrazone + sulfentrazone applied PRE resulted in higher grain yields (3,343 to 4,244 kg ha-1). These results conclude that two-pass strategies tested in this research can consistently provide effective control of GR waterhemp in DR soybean in NY.