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Response of Palmer Amaranth Accessions in South Carolina to Selected Herbicides
Published online by Cambridge University Press: 13 November 2024
Abstract
Palmer amaranth resistant to dicamba, glufosinate, and protoporphyrinogen oxidase inhibitors has been documented in several southern states. With extensive use of these and other herbicides in South Carolina, a survey was initiated in the fall of 2020 and repeated in the fall of 2021 and 2022 to determine the relative response of Palmer amaranth accessions to selected preemergence (PRE) and postemergence (POST) herbicides. A greenhouse screening experiment was conducted where accessions were treated with three PRE (atrazine, s-metolachlor, and isoxaflutole) and six POST (glyphosate, thifensulfuron-methyl, fomesafen, glufosinate, dicamba, 2,4-D) herbicides at the 1× and 2× use rates. Herbicides were applied shortly after planting (PRE) or at the 2 to 4 leaf growth stage (POST). Percent survival was evaluated 5-14 days after application depending on herbicide activity. Sensitivity to atrazine PRE was lower for 49 and 33 accessions out of 115 to atrazine PRE at the 1× and 2× rate, respectively. Most of the accessions (90%) were controlled by isoxaflutole PRE at the 1× rate. Response to S-metolachlor PRE indicated 34% of the Palmer amaranth accessions survived the 1× rate (>60% survival). There were 11 accessions with reduced sensitivity to fomesafen POST; however, these percentages were not different from the 0% survivor group. Glyphosate POST at the 1× rate did not control most accessions (79%). Palmer amaranth response to thifensulfuron-methyl POST varied across the accessions, with only 36 and 28% controlled at the 1× and 2×rate, respectively. All accessions were controlled by 2,4-D, dicamba, or glufosinate POST. Palmer amaranth accessions from this survey exhibited reduced susceptibility to several herbicides commonly used in agronomic crops in South Carolina. Therefore, growers should continue to utilize multiple management tactics to minimize the evolution of herbicide resistance in Palmer amaranth in South Carolina.
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- This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives licence (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is unaltered and is properly cited. The written permission of Cambridge University Press must be obtained for commercial re-use or in order to create a derivative work.
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- © Weed Science Society of America, 2024