Control of annual ryegrass with spring-applied herbicides prior to seeding corn

Four field experiments were conducted over a 2 yr period (2017 and 2018) in Ontario to determine the control of annual ryegrass (ARG) seeded in the fall of 2016 and 2017 (as a cover crop) with spring-applied glyphosate alone and in a tankmixure with clethodim, fluazifop-P-butyl, quizalofop-P-butyl, sethoxydim, or saflufenacil prior to seeding glyphosate-resistant corn. The doses of glyphosate needed to provide 50%, 80%, and 90% control of ARG were 439, 1757, and >2700 g a.e. ha-1 at 3 wk after treatment application (WAA); 526, 2105, and >2700 g a.e. ha-1 at 4 WAA; and 703, >2700, and >2700 g a.e. ha-1 at 6 WAA, respectively. Glyphosate (1350 g a.e. ha-1) controlled ARG 27%, 61%, 77%, 72%, and 68% at 1, 2, 3, 4, and 6 WAA, respectively. The tankmix of glyphosate (1350 a.e. ha-1) with clethodim (30 g a.i. ha-1), fluazifop-P-butyl (125 g a.i. ha-1), quizalofop-P-ethyl (36 g a.i. ha-1), sethoxydim (150 g a.i. ha-1), or saflufenacil (25 g a.i. ha-1) controlled ARG as much as 82%, 79%, 82%, 84%, and 81%, respectively. ARG control with the tankmixes of glyphosate (1350 a.e. ha-1) with the Group 1 herbicides evaluated increased corn yield as much as 66%. Additionally, reduced ARG interference with the tankmix of glyphosate (1350 a.e. ha-1) +saflufenacil (25 g a.i. ha-1) increased corn yield 69%. The best control of ARG was achieved with high doses of glyphosate alone and glyphosate (1350 g a.e. ha-1) tankmixed with a Group 1 herbicide or saflufenacil.