Improving the Level and Consistency of Glyphosate-Resistant Canada Fleabane (Erigeron canadensis L.) Control in Soybean [Glycine max (L.) Merr.] with Preplant Herbicides
Six studies consisting of twenty four field experiments were conducted in 2020 and 2021 in Ontario, Canada to investigate how to improve the level and consistency of glyphosate-resistant (GR) Canada fleabane control with herbicides applied preplant (PP) to soybean. Study One concluded the adding saflufenacil or metribuzin to glyphosate plus halauxifen-methyl or pyraflufen-ethyl/2,4-D resulted in a synergistic increase in GR Canada fleabane control and improved the consistency of control. Study Two and Three determined adding dicamba or saflufenacil to glyphosate plus bromoxynil and adding saflufenacil to glyphosate plus dicamba improved the level and consistency of GR Canada fleabane control. Study Four determined adding metribuzin to glyphosate plus glufosinate provided the greatest level of GR Canada fleabane control and improved the consistency of control. Study Five and Six determined there was no benefit of adding low rates of protoporphyrinogen oxidase (PPO)-inhibiting herbicides to glufosinate to improve GR Canada fleabane control.