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Accepted manuscript

Optimization of Metamitron Rate Applied PRE in Sugar Beet for Management of Palmer amaranth (Amaranthus palmeri S. Watson)

Published online by Cambridge University Press:  19 June 2026

Abraham Akuoko Open the ORCID record for Abraham Akuoko [Opens in a new window] ,
Philip Westra ,
Andrew R. Kniss Open the ORCID record for Andrew R. Kniss [Opens in a new window]  and
Nevin C. Lawrence Open the ORCID record for Nevin C. Lawrence [Opens in a new window]
Abraham Akuoko
Affiliation:
Graduate Research Assistant, Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE, USA
Philip Westra
Affiliation:
Professor, Department of Agricultural Biology, Colorado State University, CO, USA
Andrew R. Kniss
Affiliation:
Professor, Department of Plant Sciences, University of Wyoming, Laramie, WY, USA
Nevin C. Lawrence*
Affiliation:
Associate Professor, Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Panhandle Research and Extension Center, Scottsbluff, NE, USA.
*
Author for correspondence: Nevin C. Lawrence, Associate Professor, Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Panhandle Research and Extension Center, 4502 Ave I, Scottsbluff, NE, 69361, USA. (E-mail: nlawrence2@unl.edu).
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Abstract

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The prevalence of glyphosate- and ALS-inhibitor-resistant Palmer amaranth has substantially impacted sugar beet yield across CO and NE since 2020. While metamitron applied PRE has been previously reported to effectively control glyphosate-resistant (GR) Palmer amaranth, the rates evaluated in the literature are likely higher than what is practical for growers. Consequently, identifying an optimal rate will reduce potential herbicide use while still effectively controlling Palmer amaranth. Lower rates of metamitron may be sufficient to allow control of Palmer amaranth through the two true-leaf stage (2 TL) of growth, where very-long chain fatty acid (VLCFA) inhibiting herbicides can be used to layer additional residual herbicides and prevent Palmer amaranth emergence. Multiple dose-response analysis studies were established in Nebraska in 2020 and 2023, and in Colorado in 2023, to determine the necessary rate of metamitron, with and without a tank-mix partner of ethofumesate, to control Palmer amaranth through the 2 TL sugar beet stage. Metamitron rates ranged from 0 – 6.40 kg ai ha-1, while ethofumesate was included at a fixed rate of 1.68 and 1.86 kg ai ha-1 in 2020 and 2023, respectively. At all locations, maximum Palmer amaranth control was obtained near 4 kg ai ha-1 when applied alone. Adding ethofumesate as a tank-mix partner reduced metamitron use rate to about 2.9 kg ai ha-1. Trial results supported the issuance of a Section 18 label for metamitron at 3.27 kg ai ha-1 in Colorado and Nebraska in 2024, which subsequently extended to include Idaho, Wyoming, and Oregon in 2025.

Keywords

EthofumesateGoltix 700 SCdose-response

Information

Type
Research Article
Information
Weed Technology , Accepted manuscript , pp. 1 - 21
Creative Commons
Creative Common License - CCCreative Common License - BYCreative Common License - NCCreative Common License - ND
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.
Copyright
© The Author(s), 2026. Published by Cambridge University Press on behalf of Weed Science Society of America