Investigating the potential of novel synergistic postemergence tank mixtures to manage HPPD- and atrazine-resistant Amaranthus tuberculatus populations

Jacobs Jr, Kip Edward

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Description

Title

Investigating the potential of novel synergistic postemergence tank mixtures to manage HPPD- and atrazine-resistant Amaranthus tuberculatus populations

Author(s)

Jacobs Jr, Kip Edward

Issue Date

2021-10-19

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

Riechers, Dean E

Committee Member(s)

• Riggins, Chance W
• Butts-Wilmsmeyer, Carrie J

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)

• Waterhemp
• Resistance
• HPPD-inhibitors

Abstract

Chapter 1 includes a literature review of photosystem II-(PSII), phytoene desaturase- (PDS), and 4-hydroxyphenylpyruvate dioxygenase-(HPPD) inhibiting herbicides including their target sites, mode of action and resistance. The Group 5, or PS II-inhibiting herbicides, act by blocking electron transport within PSII in plants. PSII inhibitors compete with plastoquinone (PQ) for the Qb binding site of the D1 protein, causing a unique symptomology that appears on older plant leaves since these herbicides are only xylem mobile and not ion trapped in the phloem. Pigment-inhibiting herbicides, such as the Group 12 herbicides, are commonly used preemergence (PRE) in crops such as cotton, wheat and barley. PDS-inhibiting herbicides directly inhibit the carotenoid portion of the terpenoid pathway. Inhibition of PDS results in the accumulation of phytoene and depletion of carotenoids. Inhibition of the HPPD enzyme by Group 27 herbicides blocks the second step of tyrosine catabolism to PQ, which is important for electron transport in photosynthesis and as an electron acceptor in carotenoid biosynthesis, as well as tocopherols (vitamin E). HPPD inhibitors also indirectly affect the PDS reaction since this enzyme requires PQ as a cofactor. Waterhemp (Amaranthus tuberculatus) and Palmer amaranth (A. palmeri) are the only two species in the United States that have evolved resistance to HPPD- and PSII-inhibiting herbicides. Waterhemp is a small-seeded, dioecious, summer annual dicot weed species in the Amaranthaceae family and is native to Illinois. Discontinuous germination, C4 photosynthesis, and prolific seed output are some of the characteristics that make waterhemp concerning for growers. Waterhemp has displayed resistance to herbicides from seven different site-of-action groups as a species, including: acetolactate synthase (ALS) inhibitors, 5-enolpyruvyl-shikimate-3-phosphate (EPSPS) inhibitors, protoporphyrinogen oxidase (PPO) inhibitors, synthetic auxins, PSII inhibitors, HPPD inhibitors, and very-long-chain fatty acid (VLCFA) inhibitors. As a result, new herbicide tank mixtures need to be investigated to improve waterhemp management in corn and soybeans. Chapter 2 describes field experiments conducted at three locations in Illinois and greenhouse experiments with postemergence (POST) tank mixtures containing mesotrione with seed collected from the McLean County resistant site. Field and greenhouse studies were designed to investigate the PDS and PSII-inhibiting herbicides, norflurazon and metribuzin, respectively, as components of two- and three-way POST tank mixtures for managing atrazine- and HPPD-inhibitor-resistant waterhemp. Studies were conducted at two locations (Champaign County, Illinois (CHR), McLean County, Illinois (MCR)) during 2019 and 2020 that contain multiple herbicide-resistant (MHR) waterhemp. Treatments included one of three commercial HPPD-inhibiting herbicides (mesotrione, tembotrione, or topramezone) tank mixed with a reduced rate of metribuzin, norflurazon, or both to investigate the hypothesis of obtaining greater control of MHR waterhemp with two- and three-way tank mixtures compared to the individual active ingredients, and to assess the potential benefit of including norflurazon. Field study results indicated the addition of norflurazon to HPPD-inhibiting herbicides increased waterhemp control (approximately 30%) compared to individual herbicides applied alone. Additionally, metribuzin in combination with HPPD-inhibiting herbicides consistently increased control of MHR waterhemp populations compared to the herbicides applied alone. However, only the three-way tank mixture containing tembotrione at the MCR site reduced biomass relative to two-way treatments containing tembotrione, metribuzin, or norflurazon. Greenhouse experiments were designed to further characterize the effect of applying norflurazon with metribuzin and a representative HPPD-inhibiting herbicide from the triketone (mesotrione) or pyrazolone (topramezone) subclasses. These experiments indicated a significant reduction in waterhemp biomass when metribuzin was mixed with HPPD inhibitors in comparison to the individual components applied alone. Two-way tank mixtures containing norflurazon resulted in a significant reduction in biomass in combination with mesotrione or metribuzin when compared to the individual active ingredients applied alone. The three-way mixture provided greater control of the SIR population (analogous to MCR) than the two-way treatment of metribuzin and mesotrione. Greenhouse experiments also indicated decreased control, or antagonism, when norflurazon was mixed with topramezone in comparison to topramezone alone. The three-way mixture with topramezone also decreased control in comparison to the two-way combination of metribuzin and topramezone. Combined results from field and greenhouse experiments demonstrated norflurazon and metribuzin are effective tank-mix partners with HPPD-inhibiting herbicides for control of MHR waterhemp. The addition of a PDS inhibitor to previously studied tank mixtures allowed for a novel expansion of prior research involving HPPD- and PSII-inhibitors, although crop tolerance was not investigated in these experiments. Future research needs to be conducted to further investigate the potential niche of combining these three herbicide classes in tank mixtures in row crop production, such as studying PRE vs. POST applications and herbicide safeners in corn. Varying rate structures (depending on soil texture and organic matter) should also be investigated. Other herbicides (e.g., PPO and VLCFA inhibitors) that provide soil-residual control of waterhemp should be examined as tank-mix partners, as well as other PDS inhibitors (e.g., diflufenican) that may display more activity on waterhemp.

Graduation Semester

2021-12

Type of Resource

Thesis

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http://hdl.handle.net/2142/113821

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Copyright 2021 Kip Jacobs Jr

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