Evaluation of Bromoxynil, Pyraflufen-ethyl/2,4-D, and Tiafenacil for the Control of Glyphosate-resistant Canada fleabane (Conyza canadensis) in Soybean (Glycine max) and Metribuzin for the Control of Waterhemp (Amaranthus tuberculatus) with Two Mechanisms of Resistance to Photosystem II-inhibiting herbicides




Westerveld, David

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University of Guelph


Fifteen field experiments were conducted in 2019 and 2020 to evaluate bromoxynil, pyraflufen-ethyl/2,4-D, and tiafenacil, alone and tankmixed with metribuzin, for the control of glyphosate-resistant (GR) Canada fleabane applied preplant in soybean. The biologically-effective-dose (BED) of bromoxynil +/- metribuzin, pyraflufen-ethyl/2,4-D +/- metribuzin, and tiafenacil +/- metribuzin was determined. Bromoxynil, pyraflufen-ethyl/2,4-D, and tiafenacil, tankmixed with metribuzin, provided similar control to the current industry standards at 8 weeks after application (WAA). Ten field and eight greenhouse experiments were conducted to evaluate metribuzin, applied preemergence (PRE) and postemergence (POST), for the control of photosystem II (PS II)-inhibitor resistant waterhemp conferred by target-site resistance (TSR) and non-target-site resistance (NTSR) mechanisms. In both the field and greenhouse studies NTSR PS II-inhibitor resistant waterhemp was controlled with metribuzin applied PRE and POST, in contrast TSR PS II-inhibitor resistant waterhemp was not controlled with metribuzin.



Waterhemp, Canada fleabane, Metribuzin, Bromoxynil, Tiafenacil, Pyraflufen-ethyl/2,4-D, Glyphosate


Westerveld, D., Soltani, N., Hooker, D., Robinson, D., & Sikkema, P. (2021). Biologically-Effective-Dose of Bromoxynil, Applied Alone and Mixed with Metribuzin, for the Control of Glyphosate-Resistant Horseweed in Soybean. Weed Technology, 1-22. doi:10.1017/wet.2021.12