Herbicide-Resistant Palmer amaranth (Amaranthus palmeri S. Wats.) in the United States — Mechanisms of Resistance, Impact, and Management

Cotton growers rely heavily upon glufosinate and various residual herbicides applied preplant, PRE, and POST to control Palmer amaranth resistant to glyphosate and acetolactate synthase-inhibiting herbicides. Recently deregulated in the United States, cotton resistant to dicamba, glufosinate, and glyphosate (B2XF cotton) offers a new platform for controlling herbicide-resistant Palmer amaranth. A field experiment was conducted in North Carolina and Georgia to determine B2XF cotton tolerance to dicamba, glufosinate, and glyphosate and to compare Palmer amaranth control by dicamba to a currently used, nondicamba program in both glufosinate- and glyphosate-based systems. Treatments consisted of glyphosate or glufosinate applied early POST (EPOST) and mid-POST (MPOST) in a factorial arrangement of treatments with seven dicamba options (no dicamba, PRE, EPOST, MPOST, PRE followed by [fb] EPOST, PRE fb MPOST, and EPOST fb MPOST) and a nondicamba standard. The nondicamba standard consisted of fomesafen PRE, pyrithiobac EPOST, and acetochlor MPOST. Dicamba caused no injury when applied PRE and only minor, transient injury when applied POST. At time of EPOST application, Palmer amaranth control by dicamba or fomesafen applied PRE, in combination with acetochlor, was similar and 13 to 17% greater than acetochlor alone. Dicamba was generally more effective on Palmer amaranth applied POST rather than PRE, and two applications were usually more effective than one. In glyphosate-based systems, greater Palmer amaranth control and cotton yield were obtained with dicamba applied EPOST, MPOST, or EPOST fb MPOST compared with the standard herbicides in North Carolina. In contrast, dicamba was no more effective than the standard herbicides in the glufosinate-based systems. In Georgia, dicamba was as effective as the standard herbicides in a glyphosate-based system only when dicamba was applied EPOST fb MPOST. In glufosinate-based systems in Georgia, dicamba was as effective as standard herbicides only when dicamba was applied twice.

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Palmer Amaranth (Amaranthus palmeri) Control by Glufosinate plus Fluometuron Applied Postemergence to WideStrike®Cotton

Weed Technology ◽

10.1614/wt-d-12-00158.1 ◽

2013 ◽

Vol 27 (2) ◽

pp. 291-297 ◽

Cited By ~ 14

Author(s):

Kelly A. Barnett ◽

A. Stanley Culpepper ◽

Alan C. York ◽

Lawrence E. Steckel

Keyword(s):

United States ◽

Weed Control ◽

Acetolactate Synthase ◽

The United States ◽

Palmer Amaranth ◽

Effective Control ◽

Yield Response ◽

Amaranthus Palmeri ◽

Cotton Yield ◽

Cotton Cultivar

Glyphosate-resistant (GR) weeds, especially GR Palmer amaranth, are very problematic for cotton growers in the Southeast and Midsouth regions of the United States. Glufosinate can control GR Palmer amaranth, and growers are transitioning to glufosinate-based systems. Palmer amaranth must be small for consistently effective control by glufosinate. Because this weed grows rapidly, growers are not always timely with applications. With widespread resistance to acetolactate synthase-inhibiting herbicides, growers have few herbicide options to mix with glufosinate to improve control of larger weeds. In a field study using a WideStrike®cotton cultivar, we evaluated fluometuron at 140 to 1,120 g ai ha−1mixed with the ammonium salt of glufosinate at 485 g ae ha−1for control of GR Palmer amaranth 13 and 26 cm tall. Standard PRE- and POST-directed herbicides were included in the systems. Glufosinate alone injured the WideStrike® cotton less than 10%. Fluometuron increased injury up to 25% but did not adversely affect yield. Glufosinate controlled 13-cm Palmer amaranth at least 90%, and there was no improvement in weed control nor a cotton yield response to fluometuron mixed with glufosinate. Palmer amaranth 26 cm tall was controlled only 59% by glufosinate. Fluometuron mixed with glufosinate increased control of the larger weeds up to 28% and there was a trend for greater yields. However, delaying applications until weeds were 26 cm reduced yield 22% relative to timely application. Our results suggest fluometuron mixed with glufosinate may be of some benefit when attempting to control large Palmer amaranth. However, mixing fluometuron with glufosinate is not a substitute for a timely glufosinate application.

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Management of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in 2,4-D–, glufosinate-, and glyphosate-resistant soybean

Weed Technology ◽

10.1017/wet.2020.91 ◽

2020 ◽

pp. 1-8

Author(s):

Chandrima Shyam ◽

Parminder S. Chahal ◽

Amit J. Jhala ◽

Mithila Jugulam

Keyword(s):

United States ◽

Field Experiments ◽

The United States ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Soybean Yield ◽

Chlorimuron Ethyl ◽

Density And Biomass ◽

Herbicide Programs ◽

Biomass Reduction

Abstract Glyphosate-resistant (GR) Palmer amaranth is a problematic, annual broadleaf weed in soybean production fields in Nebraska and many other states in the United States. Soybean resistant to 2,4-D, glyphosate, and glufosinate (Enlist E3TM) has been developed and was first grown commercially in 2019. The objectives of this research were to evaluate the effect of herbicide programs applied PRE, PRE followed by (fb) late-POST (LPOST), and early-POST (EPOST) fb LPOST on GR Palmer amaranth control, density, and biomass reduction, soybean injury, and yield. Field experiments were conducted near Carleton, NE, in 2018, and 2019 in a grower’s field infested with GR Palmer amaranth in 2,4-D–, glyphosate-, and glufosinate-resistant soybean. Sulfentrazone + cloransulam-methyl, imazethapyr + saflufenacil + pyroxasulfone, and chlorimuron ethyl + flumioxazin + metribuzin applied PRE provided 84% to 97% control of GR Palmer amaranth compared with the nontreated control 14 d after PRE. Averaged across herbicide programs, PRE fb 2,4-D and/or glufosinate, and sequential application of 2,4-D or glufosinate applied EPOST fb LPOST resulted in 92% and 88% control of GR Palmer amaranth, respectively, compared with 62% control with PRE-only programs 14 d after LPOST. Reductions in Palmer amaranth biomass followed the same trend; however, Palmer amaranth density was reduced 98% in EPOST fb LPOST programs compared with 91% reduction in PRE fb LPOST and 76% reduction in PRE-only programs. PRE fb LPOST and EPOST fb LPOST programs resulted in an average soybean yield of 4,478 and 4,706 kg ha−1, respectively, compared with 3,043 kg ha−1 in PRE-only programs. Herbicide programs evaluated in this study resulted in no soybean injury. The results of this research illustrate that herbicide programs are available for the management of GR Palmer amaranth in 2,4-D–, glyphosate-, and glufosinate-resistant soybean.

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Control of Protoporphyrinogen Oxidase Inhibiting Herbicide Resistant and Susceptible Palmer Amaranth (Amaranthus palmeri) with Soil-Applied Protoporphyrinogen Oxidase–Inhibiting Herbicides

Weed Technology ◽

10.1017/wet.2017.78 ◽

2017 ◽

Vol 32 (1) ◽

pp. 95-100 ◽

Cited By ~ 8

Author(s):

Alinna M. Umphres ◽

Lawrence E. Steckel ◽

Thomas C. Mueller

Keyword(s):

Cropping Systems ◽

The United States ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Relative Resistance ◽

Complete Control ◽

Protoporphyrinogen Oxidase ◽

Herbicide Resistant ◽

Herbicide Treatments ◽

Selection For

AbstractPalmer amaranth resistance to protoporphyrinogen oxidase (PPO)-inhibiting herbicides has become an increasing problem to producers throughout the southeast region of the United States. Traditionally, these herbicides can be used as foliar-applied and soil-applied in glyphosate resistant (GR) cropping systems to control GR Palmer amaranth. Heavy reliance on PPO herbicides has contributed to the increased selection for PPO inhibitor-resistant (PPO-R) Palmer amaranth biotypes. Dose response greenhouse research was conducted to evaluate the efficacy of soil-applied flumioxazin, fomesafen, saflufenacil and sulfentrazone on a known susceptible (S) and resistant (R) Palmer amaranth biotype. Both R and S populations reached maximum germination at 14 d after treatment (DAT). The data from this study suggests complete control (100%) was achieved for the S biotype at 35 d after treatment (DAT) with all herbicides. The R biotype showed difference among herbicide treatments with flumioxazin and saflufenacil having similar responses in control and fomesafen and sulfentrazone resulting in less control of the R Palmer amaranth biotypes. The calculated relative resistance factor ranged from 3.5 to 6.0, and averaged 5X for the four herbicides. This research indicated that the PPO-R population was still responsive to all tested herbicides, but a low level of resistance was present.

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Confirmation and Control of Triazine and 4-Hydroxyphenylpyruvate Dioxygenase-Inhibiting Herbicide-Resistant Palmer Amaranth (Amaranthus palmeri) in Nebraska

Weed Technology ◽

10.1614/wt-d-13-00090.1 ◽

2014 ◽

Vol 28 (1) ◽

pp. 28-38 ◽

Cited By ~ 47

Author(s):

Amit J. Jhala ◽

Lowell D. Sandell ◽

Neha Rana ◽

Greg R. Kruger ◽

Stevan Z. Knezevic

Keyword(s):

Acetolactate Synthase ◽

The United States ◽

Oxidase Inhibitor ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Corn Production ◽

Herbicide Resistant ◽

South Central ◽

Fold Level ◽

And Control

Palmer amaranth is a difficult-to-control broadleaf weed that infests corn and soybean fields in south-central and southwestern Nebraska and several other states in the United States. The objectives of this research were to confirm triazine and 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide-resistant Palmer amaranth in Nebraska and to determine sensitivity and efficacy of POST-applied corn herbicides for control of resistant and susceptible Palmer amaranth biotypes. Seeds from a putative HPPD-resistant Palmer amaranth biotype from Fillmore County, NE were collected from a seed corn production field in fall 2010. The response of Palmer amaranth biotypes to 12 rates (0 to 12×) of mesotrione, tembotrione, topramezone, and atrazine was evaluated in a dose–response bioassay in a greenhouse. On the basis of the values at the 90% effective dose (ED90) level, the analysis showed a 4- to 23-fold resistance depending upon the type of HPPD-inhibiting herbicide being investigated and susceptible biotype used for comparison. This biotype also had a 9- to 14-fold level of resistance to atrazine applied POST. Results of a POST-applied herbicide efficacy study suggested a synergistic interaction between atrazine and HPPD-inhibiting herbicides that resulted in > 90% control of all Palmer amaranth biotypes. The resistant biotype had a reduced sensitivity to acetolactate synthase inhibiting herbicides (halosulfuron and primisulfuron), a photosystem-II inhibitor (bromoxynil), and a protoporphyrinogen oxidase inhibitor (fluthiacet-methyl). Palmer amaranth biotypes were effectively controlled (≥ 90%) with glyphosate, glufosinate, and dicamba, whereas 2,4-D ester provided 81 to 83% control of the resistant biotype and > 90% control of both susceptible biotypes.

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Seedbank Persistence of Palmer Amaranth (Amaranthus palmeri) and Waterhemp (Amaranthus tuberculatus) across Diverse Geographical Regions in the United States

Weed Science ◽

10.1017/wsc.2018.27 ◽

2018 ◽

Vol 66 (4) ◽

pp. 446-456 ◽

Cited By ~ 6

Author(s):

Nicholas E. Korres ◽

Jason K. Norsworthy ◽

Bryan G. Young ◽

Daniel B. Reynolds ◽

William G. Johnson ◽

...

Keyword(s):

United States ◽

Seed Viability ◽

Soil Surface ◽

The United States ◽

Palmer Amaranth ◽

Soil Conditions ◽

Burial Depth ◽

Amaranthus Palmeri ◽

Seed Damage ◽

Amaranthus Tuberculatus

AbstractKnowledge of the effects of burial depth and burial duration on seed viability and, consequently, seedbank persistence of Palmer amaranth (Amaranthus palmeriS. Watson) and waterhemp [Amaranthus tuberculatus(Moq.) J. D. Sauer] ecotypes can be used for the development of efficient weed management programs. This is of particular interest, given the great fecundity of both species and, consequently, their high seedbank replenishment potential. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0 and 15 cm) for 3 yr. Each year, seeds were retrieved, and seed damage (shrunken, malformed, or broken) plus losses (deteriorated and futile germination) and viability were evaluated. Greater seed damage plus loss averaged across seed origin, burial depth, and year was recorded for lots tested at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) forA. palmeriandA. tuberculatus, respectively. The site differences for seed persistence were probably due to higher volumetric water content at these sites. Rates of seed demise were directly proportional to burial depth (α=0.001), whereas the percentage of viable seeds recovered after 36 mo on the soil surface ranged from 4.1% to 4.3% compared with 5% to 5.3% at the 15-cm depth forA. palmeriandA. tuberculatus, respectively. Seed viability loss was greater in the seeds placed on the soil surface compared with the buried seeds. The greatest influences on seed viability were burial conditions and time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species should focus on reducing seed shattering, enhancing seed removal from the soil surface, or adjusting tillage systems.

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Comparative growth of Palmer amaranth (Amaranthus palmeri) accessions

Weed Science ◽

10.1614/ws-04-155r2.1 ◽

2006 ◽

Vol 54 (1) ◽

pp. 121-126 ◽

Cited By ~ 27

Author(s):

Jason A. Bond ◽

Lawrence R. Oliver

Keyword(s):

United States ◽

Leaf Area ◽

Growth And Development ◽

The United States ◽

Area Ratio ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Harvest Intervals ◽

Net Assimilation ◽

Stem Leaf

A 2-yr field study was conducted to compare growth characteristics of 24 Palmer amaranth accessions collected from across the indigenous range of the species in the United States. Variation in growth and development of Palmer amaranth was noted among accessions based on leaf area ratio (LAR), specific leaf area (SLA), net assimilation rate (NAR), and stem leaf ratio (SLR), but only SLR varied across harvest intervals among accessions. Accessions collected across the range of Palmer amaranth in the United States displayed variation in growth and development based on differences in LAR, SLA, NAR, and SLR. Observed differences among accessions indicate the existence of Palmer amaranth ecotypes.

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Palmer Amaranth (Amaranthus palmeri) and Velvetleaf (Abutilon theophrasti) Control in No-Tillage Conventional (Non–genetically engineered) Soybean Using Overlapping Residual Herbicide Programs

Weed Technology ◽

10.1017/wet.2018.78 ◽

2018 ◽

Vol 33 (1) ◽

pp. 95-105 ◽

Cited By ~ 10

Author(s):

Debalin Sarangi ◽

Amit J. Jhala

Keyword(s):

United States ◽

The United States ◽

Genetically Engineered ◽

Palmer Amaranth ◽

Cost Ratio ◽

No Tillage ◽

Benefit Cost Ratio ◽

No Till ◽

Benefit Cost ◽

Herbicide Programs

AbstractDue to depressed corn and soybean prices over the last few years in the United States, growers in Nebraska are showing interest in no-tillage (hereafter referred to as no-till) conventional (non–genetically engineered [non-GE]) soybean production. Due to the increasing number of herbicide-resistant weeds in the United States, weed control in no-till non-GE soybean using POST herbicides is a challenge. The objectives of this study were to compare PRE-only, PRE followed by (fb) POST, and PRE fb POST with residual (POST-WR) herbicide programs for Palmer amaranth and velvetleaf control and soybean injury and yield, as well as to estimate the gross profit margins and benefit–cost ratio of herbicide programs. A field experiment was conducted in 2016 and 2017 at Clay Center, NE. The PRE herbicides tested in this study resulted in ≥95% Palmer amaranth and velvetleaf control at 28 d after PRE (DAPRE). Averaged across the programs, the PRE-only program controlled Palmer amaranth 66%, whereas 86% and 97% control was obtained with the PRE fb POST and PRE fb POST-WR programs, respectively, at 28 d after POST (DAPOST). At 28 DAPOST, the PRE fb POST herbicide programs controlled velvetleaf 94%, whereas the PRE-only program resulted in 85% control. Mixing soil-residual herbicides with foliar-active POST programs did not improve velvetleaf control. Averaged across herbicide programs, PRE fb POST programs increased soybean yield by 10% and 41% in 2016 and 2017, respectively, over the PRE-only programs. Moreover, PRE fb POST-WR programs produced 7% and 40% higher soybean yield in 2016 and 2017, respectively, compared with the PRE fb POST programs. The gross profit margin (US$1,184.3 ha−1) was highest under flumioxazin/pyroxasulfone (PRE) fb fluthiacet-methyl plusS-metolachlor/fomesafen (POST-WR) treatment; however, the benefit–cost ratio was highest (6.1) with the PRE-only program of flumioxazin/chlorimuron-ethyl.

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Sex-specific markers for waterhemp (Amaranthus tuberculatus) and Palmer amaranth (Amaranthus palmeri)

Weed Science ◽

10.1017/wsc.2019.27 ◽

2019 ◽

Vol 67 (4) ◽

pp. 412-418 ◽

Cited By ~ 6

Author(s):

Jacob S. Montgomery ◽

Ahmed Sadeque ◽

Darci A. Giacomini ◽

Patrick J. Brown ◽

Patrick J. Tranel

Keyword(s):

Crop Production ◽

Genetic Basis ◽

The United States ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Data Set ◽

Amaranthus Tuberculatus ◽

Primer Sets ◽

Male Specific ◽

Specific Sequences

AbstractWaterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] and Palmer amaranth (Amaranthus palmeri S. Watson) are troublesome weeds of row-crop production in the United States. Their dioecious reproductive systems ensure outcrossing, facilitating rapid evolution and distribution of resistances to multiple herbicides. Little is known, however, about the genetic basis of dioecy in Amaranthus species. In this work, we use restriction site–associated DNA sequencing (RAD-Seq) to investigate the genetic basis of sex determination in A. tuberculatus and A. palmeri. For each species, approximately 200 plants of each sex were sampled and used to create RAD-Seq libraries. The resulting libraries were separately bar-coded and then pooled for sequencing with the Illumina platform, yielding millions of 64-bp reads. These reads were analyzed to identify sex-specific and sex-biased sequences. We identified 345 male-specific sequences from the A. palmeri data set and 2,754 male-specific sequences in A. tuberculatus. An unexpected 723 female-specific sequences were identified in a subset of the A. tuberculatus females; subsequent research, however, indicated female specificity of these markers was limited to the population from which they were identified. Primer sets designed to specifically amplify male-specific sequences were tested for accuracy on multiple, geographically distinct populations of A. tuberculatus and A. palmeri, as well as other Amaranthus species. Two primer sets for A. palmeri and four primer sets for A. tuberculatus were each able to distinguish between male and female plants with at least 95% accuracy. In the near term, sex-specific markers will be useful to the A. tuberculatus and A. palmeri research communities (e.g., to predict sex for crossing experiments). In the long-term, this research will provide the foundational tools for detailed investigations into the molecular biology and evolution of dioecy in weedy Amaranthus species.

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