Evaluating Metamitron Efficacy for Glyphosate-resistant Palmer Amaranth (Amaranthus palmeri) Management in Sugarbeet Across the Central High Plains

Authors

Abraham Akuoko, University of Nebraska-LincolnFollow

First Advisor

Nevin C. Lawrence

Committee Members

Andrew R. Kniss, Cody F. Creech, Robert Harveson

Date of this Version

12-2025

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Agronomy

Under the supervision of Professor Nevin C. Lawrence

Lincoln, Nebraska, December 2025

Comments

Copyright 2025, Abraham Akuoko. Used by permission

Abstract

Herbicide-resistant (HR) Palmer amaranth (Amaranthus palmeri S. Watson) is regarded as one of the most prominent weeds within sugarbeet fields across the Central High Plains, with limited chemical control options. Although a few herbicides are available, their use is restrictive due to crop injury concerns and can only be applied at or after the 2–4 true leaf (TL) growth stage, which will provide no control for already emerged weeds. However, Palmer amaranth often emerges between sugarbeet planting and the 2 TL sugarbeet growth stage. Consequently, as of 2023, there were no herbicide options to control Palmer amaranth in sugarbeet prior to the 2–4 TL stage, or after Palmer amaranth emerges. Research presented in this thesis focuses on the use of metamitron as a pre-crop emergence (PRE) herbicide in sugarbeet, in relation to Palmer amaranth control and crop safety. Chapter 1 reviews sugarbeet production in the United States, the most common weed species in sugarbeet production systems, the biology and management of Palmer amaranth in sugarbeet, and the available effective herbicide options in the western sugarbeet production region to manage HR-Palmer amaranth. Chapter 2 evaluated high rates of metamitron applied PRE compared to existing herbicide options, and how metamitron may be implemented with other herbicide programs. Season-long weed control of various species and sugarbeet yield were assessed. Chapter 3 is an assessment of the optimal field rate of metamitron applied PRE, alone or in combination with ethofumesate, for control of Palmer amaranth during the first six to ten weeks of the sugarbeet crop. Chapter 4 assesses crop safety of metamitron-based treatment programs at application timings that are not allowed on the herbicide label, simulating situations where a farmer is unable to make a timely application due to weather or field conditions.

Advisor: Nevin C. Lawrence