Abstract

There is limited published data on the impact of the addition of Crimson^® NG to glyphosate on weed control efficacy in corn under Ontario environmental conditions. Four field experiments were conducted at the University of Guelph, Ridgetown Campus, Ridgetown, Ontario during 2022 and 2023 with two water sources to evaluate weed control with glyphosate alone and in combination with Crimson^® NG. Glyphosate was applied at rates of 900, 1029, or 1221 g ae ha^-1, with and without Crimson^® NG at 1.0 and 2.5% v/v, using water with 56 ppm (Ridgetown) and 1600 ppm (Plattsville) hardness. Results showed that glyphosate at 900 g ae ha^-1 controlled velvetleaf, Powell amaranth, common ragweed, common lambsquarters, barnyardgrass, and giant foxtail 97-100%, independent of water hardness. Neither increased glyphosate rates nor the addition of Crimson^® NG significantly improved weed control. No corn injury was observed with all herbicide/adjuvant treatments evaluated. These findings confirm that glyphosate at 900 g ae ha^-1 is highly effective for the control of common annual grass and broadleaf weeds. Weed control efficacy with glyphosate was not influenced by water source and there was no improvement in weed control efficacy from increasing the rate of glyphosate or from the addition of Crimson^® NG.

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