Glyphosate-resistant, management, Palmer amaranth, XtendFlex soybean


XtendFlex soybean is a triple-stacked trait technology that allows growers to use dicamba (XtendiMax) and glufosinate (Liberty) for in-season control of glyphosate-resistant (GR) weed species, including Palmer amaranth. A field study was conducted at the Kansas State University Agricultural Research Center (KSU-ARCH) near Hays, KS, to determine the effectiveness of POST applied XtendiMax and Liberty alone or in sequential applications for GR Palmer amaranth control in XtendFlex soybean. The study site had a natural infestation of GR Palmer amaranth. Results showed that early post-emergence (EPOST) applications of XtendiMax or Liberty followed by (fb) a late post-emergence (LPOST) application of Liberty provided an excellent control (98%) of GR Palmer amaranth compared to XtendiMax or Liberty alone at 30 days after treatment (DAT). All treatments provided >80% control throughout the season, except for Roundup PowerMax alone (59 to 78%). Consistent with percent visual control, all tested treatments significantly reduced GR Palmer amaranth biomass (0 to 96 g/10 ft2) compared to non-treated check (178 g/10 ft2). Soybean yield for majority of the tested treatments were significantly higher (ranging from 28 to 33 bu/a), compared to nontreated check (23 bu/a). In conclusion, these results suggest that sequential treatments of EPOST XtendiMax fb LPOST XtendiMax or Liberty and EPOST Liberty fb LPOST Liberty can provide effective control of GR Palmer amaranth in XtendFlex soybeans.


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