Does Glyphosate-Resistance in Giant Ragweed (Ambrosia trifida) Influence the Efficacy of Other Active Ingredients in a Tank-mix?
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Date
2025-05
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The Ohio State University
Abstract
Herbicide-resistance in weeds, one of the most pressing concerns in modern agriculture, can manifest itself in many mechanisms, from metabolic resistance to rapid necrosis. A grower in western Ohio observed populations of giant ragweed (Ambrosia trifida L.) that had survived different burndown applications and suspected that a rapid necrosis glyphosate-resistant biotype was negatively influencing control efforts. This study examined two populations of giant ragweed for control by various tank-mixtures that did and did not include glyphosate. Population A was reported as a control failure from atrazine + s-metolachlor + mesotrione + bicyclopyrone + glyphosate. Population S was reported as a control failure from saflufenacil + atrazine + glyphosate. An experiment was initiated with these two populations of giant ragweed to evaluate control from different herbicide combinations to elucidate the control provided by these herbicide combinations. The giant ragweed seed was collected and stratified in damp sand for 8 weeks at 4°C. Seeds were treated with a 10% bleach solution and rinsed with water for 10 minutes before being placed in rolled germination paper and placed into a growth chamber. Germinated seeds were planted in soilless media. Treatments for population A included 1x labeled rate applications of glyphosate, atrazine, mesotrione, glyphosate + atrazine, glyphosate + mesotrione, atrazine + mesotrione, glyphosate + atrazine + mesotrione + bicyclopyrone, and an untreated control. Treatments for population S included 1x labeled rate applications of glyphosate, atrazine, saflufenacil, glyphosate + atrazine, glyphosate + saflufenacil, atrazine + saflufenacil, glyphosate + atrazine + saflufenacil, and an untreated control. These populations were sprayed with a single-nozzle track spray chamber and control ratings (%) were taken at 14 and 21 days after treatment (DAT). The trial was terminated 21 DAT and plants were harvested at the soil surface, dried down at 60°C for three days, and weighed to collect biomass data. This data was analyzed to assess control efficacy and examine trends. For population A, there was no difference in herbicide treatments, with or without the inclusion of glyphosate at 14 or 21 DAT, other than glyphosate alone and the untreated control which had reduced control. The biomass of plants in population A was greatest for the untreated, followed by glyphosate, then followed by the rest of the treatment groups, which were not significantly different than each other. There were similar responses observed with population S. Although both populations had characteristics that suggested the rapid response resistance trait to glyphosate, the results of this study suggest that this likely did not result in the control failures observed in the field.
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Keywords
Glyphosate, Resistance, Herbicide, Giant Ragweed