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1 June 2017 Herbicide Management Strategies in Field Corn for a Three-Way Herbicide-Resistant Palmer Amaranth (Amaranthus palmeri) Population
Jonathon R. Kohrt, Christy L. Sprague
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Abstract

Three field experiments were conducted from 2013 to 2015 in Barry County, MI to evaluate the effectiveness of PRE, POST, and one- (EPOS) and two-pass (PRE followed by POST) herbicide programs for management of multiple-resistant Palmer amaranth in field corn. The Palmer amaranth population at this location has demonstrated resistance to glyphosate (Group 9), ALS-inhibiting herbicides (Group 2), and atrazine (Group 5). In the PRE only experiment, the only herbicide treatments that consistently provided ~80% or greater control were pyroxasulfone and the combination of mesotrione S-metolachlor. However, none of these treatments provided season-long Palmer amaranth control. Only topramezone provided >85% Palmer amaranth control 14 DAT, in the POST only experiment. Of the 19 herbicide programs studied all but three programs provided ≥88% Palmer amaranth control at corn harvest. Herbicide programs that did not control Palmer amaranth relied on only one effective herbicide site of action and in one case did not include a residual herbicide POST for late-season Palmer amaranth control. Some of the EPOS treatments were effective for season-long Palmer amaranth control; however, application timing and the inclusion of a residual herbicide component will be critical for controlling Palmer amaranth. The programs that consistently provided the highest levels of season-long Palmer amaranth control were PRE followed by POST herbicide programs that relied on a minimum of two effective herbicide sites of action and usually included a residual herbicide for late-season control.

Nomenclature: Atrazine; glyphosate; mesotrione; pyroxasulfone; S-metolachlor; Palmer amaranth, Amaranthus palmeri S. Wats.; corn, Zea mays L.

© Weed Science Society of America, 2017
Jonathon R. Kohrt and Christy L. Sprague "Herbicide Management Strategies in Field Corn for a Three-Way Herbicide-Resistant Palmer Amaranth (Amaranthus palmeri) Population," Weed Technology 31(3), 364-372, (1 June 2017). https://doi.org/10.1017/wet.2017.18
Received: 8 December 2016; Accepted: 1 February 2017; Published: 1 June 2017
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KEYWORDS
Herbicide sites of action
multiple-resistance
Palmer amaranth control
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