Soil- and foliar-applied tank-mix combinations to improve management of palmer amaranth and waterhemp

Koester, Devin William

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https://hdl.handle.net/2142/127280 Copy

Description

Title

Soil- and foliar-applied tank-mix combinations to improve management of palmer amaranth and waterhemp

Author(s)

Koester, Devin William

Issue Date

2024-12-10

Director of Research (if dissertation) or Advisor (if thesis)

• Riechers, Dean E
• Branham, Bruce E

Committee Member(s)

• Below, Frederick E
• Hager, Aaron G

Department of Study

Crop Sciences

Discipline

Crop Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Palmer amaranth
• waterhemp
• tank-mix

Abstract

Palmer amaranth (Amaranthus palmeri S. Wats.) and waterhemp (A. tuberculatus (Moq) Sauer) are two problematic, small-seeded, dioecious weed species with variable seed dormancy that are both capable of drastically reducing grain yield in row crop systems. The proliferation of these species results in part from high seed production and genetic recombination, leading to the spread of resistance alleles and the development of multiple herbicide-resistant (MHR) populations. Resistant populations have survived both postemergence (POST) and preemergence (PRE) herbicide applications, highlighting the need to diversify chemistries across all application timings. Herbicide interactions between atrazine, a photosystem II (PSII) inhibitor, and mesotrione, a 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide, have resulted in synergistic control of waterhemp. Chemical combinations proved to be an effective strategy for controlling a PSII- and HPPD-inhibitor-resistant Palmer amaranth population using labeled herbicide rates of mesotrione and metribuzin, a related PSII inhibitor and atrazine substitute, in the greenhouse environment. Additional research was conducted to investigate Amaranthus weed control using metribuzin as an atrazine replacement, along with a phytoene desaturase-inhibiting herbicide, norflurazon, in PRE tank mixes aimed at improving corn production. Chapter 1 consists of a literature review describing the biology of Palmer amaranth and waterhemp, resistance mechanisms, resistance to specific herbicides used in these studies, and the efficacy and importance of tank-mixing herbicides. Chapter 2 describes my initial greenhouse experiments that quantified resistance indexes (RIs) and the overall response of two HPPD- and atrazine-resistant populations (SYNR1 and SYNR2) compared to two sensitive populations (PPI1 and PPI2) when treated with the HPPD-inhibiting herbicides, mesotrione and topramezone, and the PSII-inhibiting herbicide, metribuzin. Plant responses showed all populations were more sensitive to topramezone than to mesotrione, while resistance to metribuzin was not observed in any population. Tank-mix combinations were an effective method of POST weed control, and improved control was observed in both sensitive and resistant populations. Chapter 3 builds on the concepts from Chapter 2, applying them to a PRE tank mix field scenario that examines Amaranthus weed control within corn production systems. A phytoene desaturase (PDS) inhibitor, norflurazon, was included in this study to evaluate the impact of this additional site-of-action (SOA) on residual weed control. Results showed these herbicides may help extend the effectiveness and control window of PRE herbicide programs but cannot be relied upon as a single SOA. Additionally, norflurazon caused significant crop injury, indicating that crop safeners, different formulations, or other chemistries within the group of PDS inhibitors need to be examined.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127280

Copyright and License Information

Copyright 2024 Devin Koester

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