Control of glyphosate-resistant horseweed (Conyza canadensis) with tiafenacil mixes in corn

摘要

Abstract Four field experiments were completed in commercial corn fields during 2019 and 2020 to determine glyphosate-resistant (GR) horseweed control in corn with tiafenacil alone or in combination with bromoxynil, dicamba, or tolpyralate applied preplant (PP). Corn planted 1 to 10 d after herbicide application was not injured with any of the herbicides tested. GR horseweed interference reduced corn grain yield 32 when left uncontrolled. Herbicides reduced GR horseweed interference and resulted in corn grain yield that was similar to the weed-free control. Glyphosate (900 g ae ha−1) + tiafenacil at 12.5, 25, and 37.5 g ha−1 controlled GR horseweed 63, 68, and 72 at 4 wk after treatment (WAT) and decreased GR horseweed density 64, 43, and 83 and dry biomass 69, 55, and 83, respectively. Glyphosate + tiafenacil at 12.5, 25, and 37.5 g ha−1 plus bromoxynil (280 g ai ha−1) controlled GR horseweed 81, 88, and 87 at 4 WAT and reduced GR horseweed density 82, 94, and 93 and dry biomass 93, 93, and 98, respectively. Glyphosate + tiafenacil at 12.5, 25, and 37.5 g ha−1 plus dicamba (300 g ai ha−1) controlled GR horseweed 86, 88, and 88 at 4 WAT and decreased GR horseweed density 76, 89, and 86 and dry biomass 94, 98, and 98, respectively. Glyphosate + tiafenacil at 12.5, 25, and 37.5 g ha−1 plus tolpyralate (30 g ai ha−1) controlled GR horseweed 90, 90, and 91 at 4 WAT and decreased GR horseweed density 93, 91, and 95 and dry biomass 98, 97, and 97, respectively. The industry standards in Ontario, glyphosate + dicamba/atrazine and glyphosate + saflufenacil/dimethenamid-p controlled GR horseweed 95 and 100 at 4, 8, and 12 WAT and caused 99 and 100 density or biomass reduction, respectively.