Abstract

There is limited information on the sensitivity of corn, soybean, and winter wheat to tiafenacil applied preplant (PP) in Ontario. A total of 14 field experiments were conducted in southwestern Ontario to assess the sensitivity of no-till corn, no-till soybean, and no-till winter wheat to tiafenacil applied PP at various doses. Tiafenacil applied 1 day PP at 12.5, 25, 50, 75, 100, and 200 g ai ha^-1 caused no visible injury in corn and had no adverse effect on population, dry weight, height, maturity (as measured by seed moisture content at harvest), and seed yield.  At Ridgetown in 2019, tiafenacil applied 1 day PP at 12.5, 25, 50, 75, and 150 g ai ha^-1 caused 0, 2, 4, 8, and 14% soybean injury at 2 weeks after emergence (WAE); however, the injury was transient with no injury at 4 WAE and beyond with all tiafenacil doses evaluated, except at the highest dose (150 g ai ha^-1) which caused 5% visible soybean injury at 4 WAE. In contrast, there was no visible soybean injury in the other four environments evaluated. At all environments, soybean population, dry biomass, height, maturity, and seed yield were not adversely impacted by tiafenacil applied 1 day PP at the doses evaluated. The application of tiafenacil (25, 50, and 100 g ai ha^-1) applied 14-, 7- and 1-day PP did not cause any visible winter wheat injury in all environments evaluated, except at Huron Research Station in 2021 where 2 and 4% visible injury was observed with tiafenacil applied at 100 g ai ha^-1 at 14- and 1-day PP, respectively, at 4 WAE. The application of tiafenacil (25, 50, and 100 g ai ha^-1) applied 14-, 7- and 1-day preplant did not cause any adverse effect on winter wheat maturity or seed yield in all environments. Based on these results, tiafenacil can be applied safely at the doses and application timings evaluated to control/suppress emerged sensitive weeds in no-till corn, no-till soybean, and no-till winter wheat.

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