The utility of saflufenacil on glyphosate-resistant horseweed and its effect on select soybean varieties

Abstract

Glyphosate-resistant (GR) horseweed [Conyza canadensis (L.) Cronq.] is a major weed in soybean [Glycine max (L.) Merr.] production across the United States. Saflufenacil is a new herbicide labeled for control of GR horseweed in soybean. Due to sensitivity concerns, applications are restricted to 30 days preplant (DPP) on coarse-textured soils with less than 2% organic matter (OM). The utility of saflufenacil tank-mixes on GR and glyphosate-susceptible (GS) horseweed was evaluated in the greenhouse. Saflufenacil at 25 g ai ha-1 tank-mixed with glyphosate at 874 g ae ha-1 resulted in better control of GR and GS horseweed than either product applied alone. In field studies, saflufenacil tank-mixes were applied 30, 15, and 0 DPP to soybean on a coarse-textured and a medium-textured soil. Saflufenacil applied at 50 g ai ha-1 caused a 15-30% reduction to yield and yield components when applied 15 and 0 DPP on the coarse-textured soil.