Influence of Soybean (Glycine max) Population and Herbicide Program on Palmer Amaranth (Amaranthus palmeri) Control, Soybean Yield, and Economic Return

Palmer amaranth (Amaranthus palmeri S. Wats) has become one of the most prominent and difficult weeds to control in soybean (Glycine max (L.) Merr.) in North Carolina. A survey was conducted in North Carolina during fall 2010 to estimate the magnitude of this problem. Palmer amaranth was present in 39% of 2,512 fields representing 0.24% of soybean ha in North Carolina. In recent years, growers have reduced soybean seeding rates in an effort to decrease production costs associated with technology fees. However, given the increase in prevalence of Palmer amaranth and the difficultly in controlling this weed due to herbicide resistance, growers may need to reconsider reductions in seeding rates. Therefore, research was conducted during 2010 and 2011 to determine if Palmer amaranth control, soybean yield, and economic return were affected by soybean plant population, preemergence (PRE) and postemergence (POST) herbicides, and herbicide resistant traits (glufosinate-resistant and glyphosate-resistant cultivars). Applying PRE or POST herbicides and increasing soybean population increased Palmer amaranth control, soybean yield, and economic return when compared with POST herbicides only or when lower soybean populations were present. Efficacy of glufosinate and glyphosate did not vary in most instances, most likely because these herbicides were applied timely, and the frequency of glyphosate resistance did not exceed 10% in these fields.

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Management of Palmer Amaranth (Amaranthus palmeri) in Glufosinate-Resistant Soybean (Glycine max) with Sequential Applications of Herbicides

ISRN Agronomy ◽

10.5402/2012/131650 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Amy E. Hoffner ◽

David L. Jordan ◽

Aman Chandi ◽

Alan C. York ◽

E. James Dunphy ◽

...

Keyword(s):

North Carolina ◽

Glycine Max ◽

Plant Population ◽

Palmer Amaranth ◽

Soybean Plant ◽

Amaranthus Palmeri ◽

Single Application ◽

Soybean Yield ◽

Herbicide Treatments

Palmer amaranth (Amaranthus palmeri S. Wats.) is one of the most difficult weeds to control in soybean (Glycine max (L.) Merr.) in North Carolina. Research was conducted during 2010 and 2011 to determine if Palmer amaranth control and soybean yield were affected by soybean plant population and combinations of preemergence (PRE) herbicides followed by a single application of glufosinate postemergence (POST) versus multiple applications of glufosinate POST. Palmer amaranth was controlled more and soybean yield was greater when soybean was established at 483,000 plants ha−1 in 3 of 4 experiments compared with soybean at 178,000 plants ha−1 irrespective of herbicide treatments. In separate experiments, application of PRE herbicides followed by POST application of glufosinate or multiple POST applications of glufosinate provided variable Palmer amaranth control, although combinations of PRE and POST herbicides controlled Palmer amaranth the most and provided the greatest soybean yield. In 1 of 3 experiments, sequential applications of glufosinate were more effective than a single application. Yield was higher in 2 of 3 experiments when glufosinate was applied irrespective of timing of application when compared with the nontreated control. In the experiment where glufosinate was applied at various POST timings, multiple applications of the herbicide provided the best control and the greatest yield compared with single applications.

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Interference of Selected Palmer Amaranth (Amaranthus palmeri) Biotypes in Soybean (Glycine max)

International Journal of Agronomy ◽

10.1155/2012/168267 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Aman Chandi ◽

David L. Jordan ◽

Alan C. York ◽

Susana R. Milla-Lewis ◽

James D. Burton ◽

...

Keyword(s):

Glycine Max ◽

Acetolactate Synthase ◽

Dry Weight ◽

Glyphosate Resistance ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Fresh Weight ◽

Row Crops ◽

Soybean Yield ◽

Competitive Disadvantage

Palmer amaranth (Amaranthus palmeriS. Wats.) has become difficult to control in row crops due to selection for biotypes that are no longer controlled by acetolactate synthase inhibiting herbicides and/or glyphosate. Early season interference in soybean [Glycine max(L.) Merr.] for 40 days after emergence by three glyphosate-resistant (GR) and three glyphosate-susceptible (GS) Palmer amaranth biotypes from Georgia and North Carolina was compared in the greenhouse. A field experiment over 2 years compared season-long interference of these biotypes in soybean. The six Palmer amaranth biotypes reduced soybean height similarly in the greenhouse but did not affect soybean height in the field. Reduction in soybean fresh weight and dry weight in the greenhouse; and soybean yield in the field varied by Palmer amaranth biotypes. Soybean yield was reduced 21% by Palmer amaranth at the established field density of 0.37 plant m−2. When Palmer amaranth biotypes were grouped by response to glyphosate, the GS group reduced fresh weight, dry weight, and yield of soybean more than the GR group. The results indicate a possible small competitive disadvantage associated with glyphosate resistance, but observed differences among biotypes might also be associated with characteristics within and among biotypes other than glyphosate resistance.

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Palmer Amaranth (Amaranthus palmeri) Interference in Soybeans (Glycine max)

Weed Science ◽

10.1017/s0043174500076888 ◽

1994 ◽

Vol 42 (4) ◽

pp. 523-527 ◽

Cited By ~ 103

Author(s):

Tracy E. Klingaman ◽

Lawrence R. Oliver

Keyword(s):

Glycine Max ◽

Field Study ◽

Palmer Amaranth ◽

Growth And Yield ◽

Yield Reduction ◽

Amaranthus Palmeri ◽

Soybean Yield ◽

Soybean Canopy ◽

Highly Correlated

A 2-yr field study was conducted at Fayetteville, AR, to determine the effect of Palmer amaranth interference on soybean growth and yield. Palmer amaranth density had little effect on soybean height, but soybean canopy width ranged from 77 cm in the weed-free check to 35 cm in plots with 10 plants m–1of row 12 wk after emergence. Soybean yield reduction was highly correlated to Palmer amaranth biomass at 8 wk after emergence and maturity, soybean biomass at 8 wk after emergence, and Palmer amaranth density. Soybean yield reduction was 17, 27, 32, 48, 64, and 68%, respectively, for Palmer amaranth densities of 033, 0.66, 1, 2, 333, and 10 plants m–1of row. Soybean yield reduction and Palmer amaranth biomass were linear to approximately 2 Palmer amaranth m–1of row, suggesting intraspecific interference between adjacent Palmer amaranth is initiated at Palmer amaranth densities between 2 and 3.33 plants m–1of row.

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Palmer Amaranth (Amaranthus palmeri) Management in Dicamba-Resistant Cotton

Weed Technology ◽

10.1614/wt-d-15-00041.1 ◽

2015 ◽

Vol 29 (4) ◽

pp. 758-770 ◽

Cited By ~ 17

Author(s):

Charles W. Cahoon ◽

Alan C. York ◽

David L. Jordan ◽

Wesley J. Everman ◽

Richard W. Seagroves ◽

...

Keyword(s):

United States ◽

North Carolina ◽

Field Experiment ◽

Acetolactate Synthase ◽

The United States ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Cotton Yield ◽

Herbicide Resistant

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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Inheritance of Evolved Glyphosate Resistance in a North Carolina Palmer Amaranth (Amaranthus palmeri) Biotype

International Journal of Agronomy ◽

10.1155/2012/176108 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 24

Author(s):

Aman Chandi ◽

Susana R. Milla-Lewis ◽

Darci Giacomini ◽

Philip Westra ◽

Christopher Preston ◽

...

Keyword(s):

North Carolina ◽

Dose Response ◽

Genome Analysis ◽

Copy Number ◽

Single Gene ◽

Nuclear Genome ◽

Glyphosate Resistance ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Dose Responses

Inheritance of glyphosate resistance in a Palmer amaranth biotype from North Carolina was studied. Glyphosate rates for 50% survival of glyphosate-resistant (GR) and glyphosate-susceptible (GS) biotypes were 1288 and 58 g ha−1, respectively. These values for F1 progenies obtained from reciprocal crosses (GR×GSandGS×GRwere 794 and 501 g ha−1, respectively. Dose response of F1 progenies indicated that resistance was not fully dominant over susceptibility. Lack of significant differences between dose responses for reciprocal F1 families suggested that genetic control of glyphosate resistance was governed by nuclear genome. Analysis of F1 backcross (BC1F1) families showed that 10 and 8 BC1F1 families out of 15 fitted monogenic inheritance at 2000 and 3000 g ha−1glyphosate, respectively. These results indicate that inheritance of glyphosate resistance in this biotype is incompletely dominant, nuclear inherited, and might not be consistent with a single gene mechanism of inheritance. Relative 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) copy number varied from 22 to 63 across 10 individuals from resistant biotype. This suggested that variableEPSPScopy number in the parents might be influential in determining if inheritance of glyphosate resistance is monogenic or polygenic in this biotype.

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Distribution of Glyphosate- and Thifensulfuron-Resistant Palmer Amaranth (Amaranthus palmeri) in North Carolina

International Journal of Agronomy ◽

10.1155/2014/747810 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 18

Author(s):

Amy H. Poirier ◽

Alan C. York ◽

David L. Jordan ◽

Aman Chandi ◽

Wesley J. Everman ◽

...

Keyword(s):

North Carolina ◽

Crop Production ◽

Error Variance ◽

Glyphosate Resistance ◽

Palmer Amaranth ◽

Multiple Resistance ◽

Amaranthus Palmeri ◽

Row Crop ◽

Resistance Trait ◽

Als Inhibitor

Glyphosate resistance in Palmer amaranth was first confirmed in North Carolina in 2005. A survey that year indicated 17 and 18% of 290 populations sampled were resistant to glyphosate and thifensulfuron, respectively. During the fall of 2010, 274 predetermined sites in North Carolina were surveyed to determine distribution of Palmer amaranth and to determine if and where resistance to fomesafen, glufosinate, glyphosate, and thifensulfuron occurred. Palmer amaranth was present at 134 sites. When mortality for each biotype was compared to a known susceptible biotype for each herbicide within a rate, 93 and 36% of biotypes were controlled less by glyphosate (840 g ae ha−1) and thifensulfuron (70 g ai ha−1), respectively. This approach may have underestimated resistance for segregating populations due to lack of homogeneity of the herbicide resistance trait and its contribution to error variance. When mortality and visible control were combined, 98% and 97% of the populations were resistant to glyphosate and the ALS inhibitor thifensulfuron, respectively, and 95% of the populations expressed multiple resistance to both herbicides. This study confirms that Palmer amaranth is commonly found across the major row crop production regions of North Carolina and that resistance to glyphosate and ALS-inhibiting herbicides is nearly universal. No resistance to fomesafen or glufosinate was observed.

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Palmer Amaranth (Amaranthus palmeri) Control in Soybean with Glyphosate and Conventional Herbicide Systems

Weed Technology ◽

10.1614/wt-d-09-00043.1 ◽

2010 ◽

Vol 24 (4) ◽

pp. 403-410 ◽

Cited By ~ 42

Author(s):

Jared R. Whitaker ◽

Alan C. York ◽

David L. Jordan ◽

A. Stanley Culpepper

Keyword(s):

North Carolina ◽

Field Experiments ◽

Management Strategies ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Soybean Yield ◽

Late Season ◽

Southern States ◽

Narrow Row ◽

Conventional Systems

Glyphosate typically controls Palmer amaranth very well. However, glyphosate-resistant (GR) biotypes of this weed are present in several southern states, requiring the development of effective alternatives to glyphosate-only management strategies. Field experiments were conducted in seven North Carolina environments to evaluate control of glyphosate-susceptible (GS) and GR Palmer amaranth in narrow-row soybean by glyphosate and conventional herbicide systems. Conventional systems included either pendimethalin orS-metolachlor applied PRE alone or mixed with flumioxazin, fomesafen, or metribuzin plus chlorimuron followed by fomesafen or no herbicide POST.S-metolachlor was more effective at controlling GR and GS Palmer amaranth than pendimethalin; flumioxazin and fomesafen were generally more effective than metribuzin plus chlorimuron. Fomesafen applied POST following PRE herbicides increased Palmer amaranth control and soybean yield compared with PRE-only herbicide systems. Glyphosate alone applied once POST controlled GS Palmer amaranth 97% late in the season. Glyphosate was more effective than fomesafen plus clethodim applied POST. Control of GS Palmer amaranth when treated with pendimethalin orS-metolachlor plus flumioxazin, fomesafen, or metribuzin plus chlorimuron applied PRE followed by fomesafen POST was equivalent to control achieved by glyphosate applied once POST. In fields with GR Palmer amaranth, greater than 80% late-season control was obtained only with systems of pendimethalin orS-metolachlor plus flumioxazin, fomesafen, or metribuzin plus chlorimuron applied PRE followed by fomesafen POST. Systems of pendimethalin orS-metolachlor plus flumioxazin, fomesafen, or metribuzin plus chlorimuron applied PRE without fomesafen POST controlled GR Palmer amaranth less than 30% late in the season. Systems of pendimethalin orS-metolachlor PRE followed by fomesafen POST controlled GR Palmer amaranth less than 60% late in the season.

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Influence of Selected Fungicides on Efficacy of Clethodim and 2,4-DB

Peanut Science ◽

10.3146/ps11-14.1 ◽

2012 ◽

Vol 39 (2) ◽

pp. 121-126 ◽

Cited By ~ 1

Author(s):

Gurinderbir S. Chahal ◽

David L. Jordan ◽

Barbara B. Shew ◽

Rick L. Brandenburg ◽

James D. Burton ◽

...

Keyword(s):

North Carolina ◽

Sampling Interval ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Solution Ph ◽

Affect Control ◽

Solution Preparation ◽

Positive Correlations ◽

Sampling Times ◽

Large Crabgrass

Abstract A range of fungicides and herbicides can be applied to control pests and optimize peanut yield. Experiments were conducted in North Carolina to define biological and physicochemical interactions when clethodim and 2,4-DB were applied alone or with selected fungicides. Pyraclostrobin consistently reduced large crabgrass [Digitaria sanguinalis (L.) Scop.] control by clethodim. Chlorothalonil and tebuconazole plus trifloxystrobin reduced large crabgrass control by clethodim in two of four experiments while prothioconazole plus tebuconazole and flutriafol did not affect control. Palmer amaranth [Amaranthus palmeri S. Wats] control by 2,4-DB was not affected by these fungicides. Although differences in spray solution pH were noted among mixtures of clethodim plus crop oil concentrate or 2,4-DB and fungicides, the range of pH was 4.40 to 4.92 and 6.72 to 7.20, respectively, across sampling times of 0, 6, 24, and 72 h after solution preparation. Permanent precipitates were formed when clethodim, crop oil concentrate, and chlorothalonil were co-applied at each sampling interval. Permanent precipitates were not observed when clethodim and crop oil concentrate were included with other fungicides or when 2,4-DB was mixed with fungicides. Significant positive correlations were noted for Palmer amaranth control by 2,4-DB and solution pH but not for clethodim and solution pH.

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Susceptibility of palmer amaranth ( Amaranthus palmeri ) accessions in north carolina to Atrazine, Dicamba, S ‐metolachlor, and 2,4‐D

cftm ◽

10.1002/cft2.20136 ◽

2021 ◽

Author(s):

Levi D. Moore ◽

Katherine M. Jennings ◽

David W. Monks ◽

David L. Jordan ◽

Michael D. Boyette ◽

...

Keyword(s):

North Carolina ◽

Palmer Amaranth ◽

Amaranthus Palmeri

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Critical Period for Palmer Amaranth (Amaranthus palmeri) Control in Pickling Cucumber

Weed Technology ◽

10.1017/wet.2018.58 ◽

2018 ◽

Vol 32 (5) ◽

pp. 586-591

Author(s):

Samuel J. McGowen ◽

Katherine M. Jennings ◽

Sushila Chaudhari ◽

David W. Monks ◽

Jonathan R. Schultheis ◽

...

Keyword(s):

North Carolina ◽

Critical Period ◽

Relative Yield ◽

Field Studies ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Marketable Yield ◽

Yield Data ◽

Pickling Cucumber ◽

Cucumber Yield

AbstractField studies were conducted in North Carolina to determine the critical period for Palmer amaranth control (CPPAC) in pickling cucumber. In removal treatments (REM), emerged Palmer amaranth were allowed to compete with cucumber for 14, 21, 28, or 35 d after sowing (DAS) in 2014 and 14, 21, 35, or 42 DAS in 2015, and cucumber was kept weed-free for the remainder of the season. In the establishment treatments (EST), cucumber was maintained free of Palmer amaranth by hand removal until 14, 21, 28, or 35 DAS in 2014 and until 14, 21, 35, or 42 DAS in 2015; after this, Palmer amaranth was allowed to establish and compete with the cucumber for the remainder of the season. The beginning and end of the CPPAC, based on 5% loss of marketable yield, was determined by fitting log-logistic and Gompertz equations to the relative yield data representing REM and EST, respectively. Season-long competition by Palmer amaranth reduced pickling cucumber yield by 45% to 98% and 88% to 98% during 2014 and 2015, respectively. When cucumber was planted on April 25, 2015, the CPPAC ranged from 570 to 1,002 heat units (HU), which corresponded to 32 to 49 DAS. However, when cucumber planting was delayed 2 to 4 wk (May 7 and May 21, 2014 and May 4, 2015), the CPPAC lasted from 100 to 918 HU (7 to 44 DAS). This research suggested that planting pickling cucumber as early as possible during the season may help to reduce competition by Palmer amaranth and delay the beginning of the CPPAC.

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