Control of Volunteer Corn in Enlist Corn and Economics of Herbicide Programs for Weed Control in Conventional and Multiple Herbicide-resistant Soybean across Nebraska

Authors

• Adam Michael Striegel, University of Nebraska-LincolnFollow

First Advisor

Amit J. Jhala

Date of this Version

5-2020

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 Amit J. Jhala

Lincoln, Nebraska, May 2020

Chapter two of this thesis was published in Journal of Weed Technology

Chapter three of this thesis will be submitted to Agronomy Journal

Comments

Copyright 2020, Adam Michael Striegel. Used by permission

Abstract

With commercialization of multiple herbicide-resistant corn and soybean cultivars, producers have new management options for controlling herbicide-resistant weeds and volunteer corn. Corn-on-corn production systems are common in irrigated fields in southcentral Nebraska which can create issues with volunteer corn management in corn fields. Enlist corn contains a new multiple herbicide-resistant trait providing resistance to 2,4-D choline, glyphosate, and the aryloxyphenoxypropionate (FOPs). Field experiments were conducted in 2018 and 2019 at South Central Agricultural Laboratory near Clay Center, Nebraska with the objective to evaluate ACCase-inhibiting herbicides and herbicide application timing on volunteer corn control, Enlist corn injury, and yield. Glyphosate/glufosinate-resistant corn harvested the year prior was cross-planted at 49,000 seeds ha^–1 to mimic volunteer corn in Enlist corn. Application timing of FOP herbicides had no effect on Enlist corn injury or yield, and provided 97-99% control of volunteer corn at 28 d after treatment (DAT). Clethodim and sethoxydim and pinoxaden provided 84-98% and 65-71% control of volunteer corn at 28 DAT, respectively; however, resulting in 62-96% Enlist corn injury and 69-98% yield reduction. While all FOP herbicides evaluated did not cause crop injury or yield loss, quizalofop is the only labeled product as of 2020 for control of volunteer corn in Enlist corn.

Despite widespread adoption of dicamba/glyphosate-resistant soybean by producers in the United States, economic information comparing herbicide programs in glufosinate-resistant and conventional soybean is not available. Field experiments were conducted in 2018 and 2019 at five locations across Nebraska to evaluate weed control, crop safety, gross profit margin, and benefit-cost ratios of herbicide programs with three unique sites of action in multiple herbicide-resistant and conventional soybean. Herbicides applied pre-emergence (PRE) that included provided 85-99% control for all weed species, and 72-96% weed biomass reductions at all locations. Herbicides applied POST provided 93-99% control for all weed species, and 89-98% weed biomass reduction 28 DAT. For individual site-years, yield was similar for many herbicide programs in herbicide-resistant and conventional systems. Gross profit margins and benefit-cost ratios were higher in herbicide-resistant systems than conventional systems, although price premiums for conventional soybean can help compensate increased herbicide costs.

Advisor: Amit J. Jhala