Abstract

Few studies have investigated the tolerance of azuki and white bean to preplant (PP) applications of tiafenacil herbicide mixtures in Ontario. Four field experiments were conducted in southwestern Ontario, Canada, to assess the tolerance of azuki and white bean to PP applications of tiafenacil and tiafenacil herbicide mixtures at 1X and 2X rates. In azuki bean, tiafenacil at the 1X and 2X rate cause 0.5 and 0.4% injury at 4 weeks after bean emergence (WAE), respectively, mixtures of tiafenacil with halauxifen-methyl plus bromoxynil at the 1X and 2X rates caused 1.3 and 4.6% injury, respectively; significantly greater compared to tiafenacil applied alone. Other tiafenacil herbicide mixtures evaluated caused similar azuki bean injury to tiafenacil applied alone. In white bean, the combinations of tiafenacil with metribuzin, 2,4-D ester, and bromoxynil + 2,4-D ester at the 2X rate caused 1.4-1.6% more visible injury than tiafenacil applied alone at the same rate; however, other herbicide mixtures caused similar injury levels to tiafenacil applied alone. None of the tiafenacil herbicide treatments evaluated reduced bean stand at 3 WAE. Tiafenacil + 2,4-D ester reduced bean biomass plant^-1 and m^-1 by 18% relative to the non-treated control at 3 WAE. At 6 WAE, none of the tiafenacil treatments evaluated affected plant height, and at harvest, none of the tiafenacil herbicide treatments influenced seed moisture content or bean yield relative to the non-treated control. These results conclude that, although certain tiafenacil mixtures may cause minor and transient injury in azuki and white bean, they do not substantially affect growth, maturity, or yield, making them suitable options for pp weed control in both azuki and white bean production.

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