Weed Management and Economics in Dicamba-Tolerant Cotton

Increasing populations of glyphosate-resistant Palmer amaranth [Amaranthus palmeri (S.) Wats.] have increased weed management costs for Texas High Plains cotton [Gossypium hirsutum (L.)] producers. The introduction of dicamba-tolerant cotton varieties and registration of dicamba formulations for postemergence use, combined with residual herbicides, can effectively control Palmer amaranth. Field studies were conducted in 2018 and 2019 near Lubbock, TX, USA to evaluate Palmer amaranth control and economics of weed management in dicamba-, glufosinate-, glyphosate-, and conventional cotton systems. The most consistent season-long Palmer amaranth control was achieved with the dicamba-tolerant system in both years. In 2018, greatest lint yields were achieved with dicamba-tolerant system when compared to the conventional and glufosinate-tolerant systems. In 2018, greatest gross margin above weed management costs were achieved with the dicamba-tolerant and glyphosate-tolerant systems. Greatest lint yield was achieved with the dicamba-tolerant and conventional systems in 2019 and greatest gross margins were achieved with the dicamba-tolerant system. Total variable costs were similar across all systems, with greater seed/technology and herbicide costs in dicamba-tolerant and glufosinate-tolerant systems, compared to higher tillage and hand hoeing costs in glyphosate-tolerant and conventional systems.

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EnlistTMWeed Control Systems for Palmer Amaranth (Amaranthus palmeri) Management in Texas High Plains Cotton

Weed Technology ◽

10.1017/wet.2017.55 ◽

2017 ◽

Vol 31 (6) ◽

pp. 793-798 ◽

Cited By ~ 4

Author(s):

Misha R. Manuchehri ◽

Peter A. Dotray ◽

J. Wayne Keeling

Keyword(s):

Control Systems ◽

Weed Management ◽

Palmer Amaranth ◽

Management Systems ◽

High Plains ◽

Amaranthus Palmeri ◽

Texas High Plains

Weed management systems were established near Lubbock, TX in 2013, 2014, and 2015 to assess the effectiveness of premixed 2,4-D choline+glyphosate alone and in combination with glufosinate and soil-residual herbicides for Palmer amaranth control. Systems consisted of trifluralin applied preplant incorporated followed by an early POST application followed by a mid-POST application. Palmer amaranth control 21 days after the early POST application ranged from 75 to 90% for all treatments that included 2,4-D choline+glyphosate alone or in a tank-mixture in 2013. Twenty-eight days after the mid-POST application, Palmer amaranth was controlled 86 to 99% for all herbicide systems with the exception of systems that included a mid-POST application of glufosinate alone. Combined across 2014 and 2015, Palmer amaranth control 21 days after the early POST application ranged from 96 to 98% for all systems that included 2,4-D choline+glyphosate, 2,4-D choline alone, or 2,4-D choline in a tank-mixture. Combined across 2014 and 2015, Palmer amaranth control 28 days after the mid-POST application ranged from 95 to 100% with the exception of the following: trifluralin preplant incorporated followed by glufosinate with or without acetochlor applied early POST followed by glufosinate mid-POST and trifluralin preplant incorporated followed by glyphosate early POST followed by glyphosate mid-POST. Overall, numerous effective systems were identified; however, systems containing 2,4-D choline+glyphosate or 2,4-D choline early POST and/or mid-POST were among the most effective. Glyphosate or glufosinate only systems or systems that relied on glufosinate alone at the mid-POST timing were inconsistent and often performed poorly.

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Palmer Amaranth (Amaranthus palmeri) Management in GlyTol®LibertyLink®Cotton

Weed Technology ◽

10.1614/wt-d-14-00029.1 ◽

2014 ◽

Vol 28 (4) ◽

pp. 592-600 ◽

Cited By ~ 5

Author(s):

Jacob D. Reed ◽

J. Wayne Keeling ◽

Peter A. Dotray

Keyword(s):

Weed Management ◽

Mixed Model ◽

Synergistic Effects ◽

Field Studies ◽

Field Trials ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Glufosinate Ammonium ◽

Model Method ◽

Expected Values

Field trials were conducted in Lubbock, TX in 2010 and 2011 to evaluate tank-mix combinations of glyphosate and glufosinate in GlyTol®LibertyLink®cotton for control of Palmer amaranth. Herbicide treatments included glyphosate and glufosinate applied at various tank-mix rate combinations (1X:1X, 1X:0.75X, 1X:0.5X, 1X:0.25X and 1X:0X of glyphosate plus glufosinate), proportional tank-mix rate combinations (1X:0X, 0.75X:0.25X, 0.5X:0.5X, 0.25X:0.75X, and 0X:1X of glyphosate plus glufosinate, where X is 0.84 kg ae ha−1of glyphosate or 0.58 kg ai ha−1of glufosinate ammonium), and in sequential (1X followed by 1X) applications of both herbicides in an overall weed management system. Greenhouse studies were conducted to quantify antagonistic or synergistic effects. Treatments included a nontreated control; glyphosate at 0.84, 0.63, 0.42, and 0.21 kg ha−1; glufosinate at 0.58, 0.44, 0.29, and 0.15 kg ha−1; and all tank-mix combinations of each herbicide rate. Dry weights were converted to percent growth values for each rate of the two herbicides alone, and these values were used to calculate expected responses of tank-mix combinations with the use of Colby's method. Expected values were compared to observed percent growth values using an augmented mixed-model method. Results of field studies indicated that tank mixes of glyphosate and glufosinate were less effective at controlling Palmer amaranth than glyphosate applied alone. The addition of any rate of glufosinate to a 1X rate of glyphosate reduced Palmer amaranth control compared to glyphosate alone. Greenhouse studies confirmed antagonism seen in the field. These results indicate that sequential applications of these two herbicides are a better option for Palmer amaranth weed management.

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Resistance to Glyphosate in Palmer Amaranth (Amaranthus palmeri) Populations from New Mexico Pecan Orchards

Weed Technology ◽

10.1614/wt-d-11-00144.1 ◽

2013 ◽

Vol 27 (1) ◽

pp. 85-91 ◽

Cited By ~ 12

Author(s):

Mohsen Mohseni-Moghadam ◽

Jill Schroeder ◽

Richard Heerema ◽

Jamshid Ashigh

Keyword(s):

New Mexico ◽

Weed Management ◽

Field Studies ◽

Mechanisms Of Action ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Financial Benefit ◽

Dona Ana County ◽

The Cost ◽

Two Populations

Two populations of Palmer amaranth suspected of being resistant to glyphosate have been reported since 2007 in pecan orchards in Doña Ana County, New Mexico. The objectives of the study were to confirm and evaluate the level of resistance, to evaluate the effectiveness of alternative herbicide mechanisms of action, and to compare the cost of effective alternative herbicides for weed management in pecan orchards. Greenhouse experiments indicated that the resistant populations were able to survive glyphosate at 736 g ae ha−1. Compared with a susceptible (S) population, one of the resistant (R) populations had sevenfold resistance to glyphosate. POST application of 12 herbicides, with five different mechanisms of action, all provided at least 88% control of both R and S populations when applied at their recommended field rates. PRE application of trifluralin and metolachlor also provided more than 99% control of R and S populations. The results of field studies indicated that the financial benefit of season-long weed management with glyphosate, in pecan orchards, was comparable with some of the tested alternative herbicides.

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Safety and efficacy of linuron with or without an adjuvant or S-metolachlor for POST control of Palmer amaranth (Amaranthus palmeri) in sweetpotato

Weed Technology ◽

10.1017/wet.2021.27 ◽

2021 ◽

pp. 1-18

Author(s):

Levi D. Moore ◽

Katherine M. Jennings ◽

David W. Monks ◽

Ramon G. Leon ◽

David L. Jordan ◽

...

Keyword(s):

Nonionic Surfactant ◽

Weed Control ◽

Critical Period ◽

Total Yield ◽

Field Studies ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Foliar Injury ◽

Protoporphyrinogen Oxidase ◽

Safety And Efficacy

Abstract Field studies were conducted to evaluate linuron for POST control of Palmer amaranth in sweetpotato to minimize reliance on protoporphyrinogen oxidase (PPO)-inhibiting herbicides. Treatments were arranged in a two by four factorial where the first factor consisted of two rates of linuron (420 and 700 g ai ha−1), and the second factor consisted of linuron applied alone or in combinations of linuron plus a nonionic surfactant (NIS) (0.5% v/v), linuron plus S-metolachlor (800 g ai ha−1), or linuron plus NIS plus S-metolachlor. In addition, S-metolachlor alone and nontreated weedy and weed-free checks were included for comparison. Treatments were applied to ‘Covington’ sweetpotato 8 d after transplanting (DAP). S-metolachlor alone provided poor Palmer amaranth control because emergence had occurred at applications. All treatments that included linuron resulted in at least 98 and 91% Palmer amaranth control 1 and 2 wk after treatment (WAT), respectively. Including NIS with linuron did not increase Palmer amaranth control compared to linuron alone, but increased sweetpotato injury and subsequently decreased total sweetpotato yield by 25%. Including S-metolachlor with linuron resulted in the greatest Palmer amaranth control 4 WAT, but increased crop foliar injury to 36% 1 WAT compared to 17% foliar injury from linuron alone. Marketable and total sweetpotato yield was similar between linuron alone and linuron plus S-metolachlor or S-metolachlor plus NIS treatments, though all treatments resulted in at least 39% less total yield than the weed-free check resulting from herbicide injury and/or Palmer amaranth competition. Because of the excellent POST Palmer amaranth control from linuron 1 WAT, a system including linuron applied 7 DAP followed by S-metolachlor applied 14 DAP could help to extend residual Palmer amaranth control further into the critical period of weed control while minimizing sweetpotato injury.

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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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Effects of Palmer Amaranth (Amaranthus palmeri) Establishment Time and Distance from the Crop Row on Biological and Phenological Characteristics of the Weed: Implications on Soybean Yield

Weed Science ◽

10.1017/wsc.2018.84 ◽

2019 ◽

Vol 67 (1) ◽

pp. 126-135 ◽

Cited By ~ 8

Author(s):

Nicholas E. Korres ◽

Jason K. Norsworthy ◽

Andy Mauromoustakos

Keyword(s):

Seed Production ◽

Weed Management ◽

Cropping Systems ◽

Management Strategies ◽

Palmer Amaranth ◽

Yield Reduction ◽

Amaranthus Palmeri ◽

Soybean Yield ◽

Management Measures ◽

Weed Population Dynamics

AbstractInformation about weed biology and weed population dynamics is critical for the development of efficient weed management programs. A field experiment was conducted in Fayetteville, AR, during 2014 and 2015 to examine the effects of Palmer amaranth (Amaranthus palmeriS. Watson) establishment time in relation to soybean [Glycine max(L.) Merr.] emergence and the effects ofA. palmeridistance from the soybean row on the weed’s height, biomass, seed production, and flowering time and on soybean yield. The establishment time factor, in weeks after crop emergence (WAE), was composed of six treatment levels (0, 1, 2, 4, 6, and 8 WAE), whereas the distance from the crop consisted of three treatment levels (0, 24, and 48 cm). Differences inA. palmeribiomass and seed production averaged across distance from the crop were found at 0 and 1 WAE in both years. Establishment time had a significant effect onA. palmeriseed production through greater biomass production and height increases at earlier dates.Amaranthus palmerithat was established with the crop (0 WAE) overtopped soybean at about 7 and 10 WAE in 2014 and 2015, respectively. Distance from the crop affectedA. palmeriheight, biomass, and seed production. The greater the distance from the crop, the higherA. palmeriheight, biomass, and seed production at 0 and 1 WAE compared with other dates (i.e., 2, 4, 6, and 8 WAE).Amaranthus palmeriestablishment time had a significant impact on soybean yield, but distance from the crop did not. The earlierA. palmeriinterfered with soybean (0 and 1 WAE), the greater the crop yield reduction; after that period no significant yield reductions were recorded compared with the rest of the weed establishment times. Knowledge ofA. palmeriresponse, especially at early stages of its life cycle, is important for designing efficient weed management strategies and cropping systems that can enhance crop competitiveness. Control ofA. palmeriwithin the first week after crop emergence or reduced distance between crop and weed are important factors for an effective implementation of weed management measures againstA. palmeriand reduced soybean yield losses due to weed interference.

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Susceptibility of Palmer amaranth (Amaranthus palmeri) to herbicides in accessions collected from the North Carolina Coastal Plain

Weed Science ◽

10.1017/wsc.2020.67 ◽

2020 ◽

Vol 68 (6) ◽

pp. 582-593

Author(s):

Denis J. Mahoney ◽

David L. Jordan ◽

Nilda Roma-Burgos ◽

Katherine M. Jennings ◽

Ramon G. Leon ◽

...

Keyword(s):

North Carolina ◽

Dose Response ◽

Coastal Plain ◽

Weed Management ◽

Acetolactate Synthase ◽

Fold Increase ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Sites Of Action ◽

Two Populations

AbstractPalmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase (ALS)-inhibiting herbicides and glyphosate are fairly common throughout the state of North Carolina (NC). This has led farm managers to rely more heavily on herbicides with other sites of action (SOA) for A. palmeri control, especially protoporphyrinogen oxidase and glutamine synthetase inhibitors. In the fall of 2016, seeds from A. palmeri populations were collected from the NC Coastal Plain, the state’s most prominent agricultural region. In separate experiments, plants with 2 to 4 leaves from the 110 populations were treated with field use rates of glyphosate, glufosinate-ammonium, fomesafen, mesotrione, or thifensulfuron-methyl. Percent visible control and survival were evaluated 3 wk after treatment. Survival frequencies were highest following glyphosate (99%) or thifensulfuron-methyl (96%) treatment. Known mutations conferring resistance to ALS inhibitors were found in populations surviving thifensulfuron-methyl application (Ala-122-Ser, Pro-197-Ser, Trp-574-Leu, and/or Ser-653-Asn), in addition to a new mutation (Ala-282-Asp) that requires further investigation. Forty-two populations had survivors after mesotrione application, with one population having 17% survival. Four populations survived fomesafen treatment, while none survived glufosinate. Dose–response studies showed an increase in fomesafen needed to kill 50% of two populations (LD50); however, these rates were far below the field use rate (less than 5 g ha−1). In two populations following mesotrione dose–response studies, a 2.4- to 3.3-fold increase was noted, with LD90 values approaching the field use rate (72.8 and 89.8 g ha−1). Screening of the progeny of individuals surviving mesotrione confirmed the presence of resistance alleles, as there were a higher number of survivors at the 1X rate compared with the parent population, confirming resistance to mesotrione. These data suggest A. palmeri resistant to chemistries other than glyphosate and thifensulfuron-methyl are present in NC, which highlights the need for weed management approaches to mitigate the evolution and spread of herbicide-resistant populations.

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Critical timing of Palmer amaranth (Amaranthus palmeri) removal in sweetpotato

Weed Technology ◽

10.1017/wet.2020.1 ◽

2020 ◽

Vol 34 (4) ◽

pp. 547-551 ◽

Cited By ~ 1

Author(s):

Stephen C. Smith ◽

Katherine M. Jennings ◽

David W. Monks ◽

Sushila Chaudhari ◽

Jonathan R. Schultheis ◽

...

Keyword(s):

North Carolina ◽

Logistic Model ◽

Yield Loss ◽

Relative Yield ◽

Field Studies ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Marketable Yield ◽

Yield Data ◽

Critical Timing

AbstractPalmer amaranth is the most common and troublesome weed in North Carolina sweetpotato. Field studies were conducted in Clinton, NC, in 2016 and 2017 to determine the critical timing of Palmer amaranth removal in ‘Covington’ sweetpotato. Palmer amaranth was grown with sweetpotato from transplanting to 2, 3, 4, 5, 6, 7, 8, and 9 wk after transplanting (WAP) and maintained weed-free for the remainder of the season. Palmer amaranth height and shoot dry biomass increased as Palmer amaranth removal was delayed. Season-long competition by Palmer amaranth interference reduced marketable yields by 85% and 95% in 2016 and 2017, respectively. Sweetpotato yield loss displayed a strong inverse linear relationship with Palmer amaranth height. A 0.6% and 0.4% decrease in yield was observed for every centimeter of Palmer amaranth growth in 2016 and 2017, respectively. The critical timing for Palmer amaranth removal, based on 5% loss of marketable yield, was determined by fitting a log-logistic model to the relative yield data and was determined to be 2 WAP. These results show that Palmer amaranth is highly competitive with sweetpotato and should be managed as early as possible in the season. The requirement of an early critical timing of weed removal to prevent yield loss emphasizes the importance of early-season scouting and Palmer amaranth removal in sweetpotato fields. Any delay in removal can result in substantial yield reductions and fewer premium quality roots.

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Weed management with CGA-362622 in transgenic and nontransgenic cotton

Weed Science ◽

10.1614/p2002-014 ◽

2003 ◽

Vol 51 (6) ◽

pp. 1002-1009 ◽

Cited By ~ 19

Author(s):

Dunk Porterfield ◽

John W. Wilcut ◽

Jerry W. Wells ◽

Scott B. Clewis

Keyword(s):

North Carolina ◽

Weed Control ◽

Weed Management ◽

Field Studies ◽

Palmer Amaranth ◽

Management Systems ◽

Weed Species ◽

Crop Tolerance ◽

Prickly Sida ◽

Smooth Pigweed

Field studies conducted at three locations in North Carolina in 1998 and 1999 evaluated crop tolerance, weed control, and yield with CGA-362622 alone and in combination with various weed management systems in transgenic and nontransgenic cotton systems. The herbicide systems used bromoxynil, CGA-362622, glyphosate, and pyrithiobac applied alone early postemergence (EPOST) or mixtures of CGA-362622 plus bromoxynil, glyphosate, or pyrithiobac applied EPOST. Trifluralin preplant incorporated followed by (fb) fluometuron preemergence (PRE) alone or fb a late POST–directed (LAYBY) treatment of prometryn plus MSMA controlled all the weed species present less than 90%. Herbicide systems that included soil-applied and LAYBY herbicides plus glyphosate EPOST or mixtures of CGA-362622 EPOST plus bromoxynil, glyphosate, or pyrithiobac controlled broadleaf signalgrass, entireleaf morningglory, large crabgrass, Palmer amaranth, prickly sida, sicklepod, and smooth pigweed at least 90%. Only cotton treated with these herbicide systems yielded equivalent to the weed-free check for each cultivar. Bromoxynil systems did not control Palmer amaranth and sicklepod, pyrithiobac systems did not control sicklepod, and CGA-362622 systems did not control prickly sida.

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Evaluation of POST-Harvest Herbicide Applications for Seed Prevention of Glyphosate-Resistant Palmer amaranth (Amaranthus palmeri)

Weed Technology ◽

10.1614/wt-d-14-00146.1 ◽

2015 ◽

Vol 29 (3) ◽

pp. 405-411 ◽

Cited By ~ 7

Author(s):

Whitney D. Crow ◽

Lawrence E. Steckel ◽

Robert M. Hayes ◽

Thomas C. Mueller

Keyword(s):

Weed Management ◽

Control Strategies ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Wheat Grain ◽

Herbicide Application ◽

Post Harvest ◽

Herbicide Treatments ◽

Soil Seedbank ◽

Residual Herbicide

Recent increases in the prevalence of glyphosate-resistant (GR) Palmer amaranth mandate that new control strategies be developed to optimize weed control and crop performance. A field study was conducted in 2012 and 2013 in Jackson, TN, and in 2013 in Knoxville, TN, to evaluate POST weed management programs applied after harvest (POST-harvest) for prevention of seed production from GR Palmer amaranth and to evaluate herbicide carryover to winter wheat. Treatments were applied POST-harvest to corn stubble, with three applications followed by a PRE herbicide applied at wheat planting. Paraquat alone or mixed withS-metolachlor controlled 91% of existing Palmer amaranth 14 d after treatment but did not control regrowth. Paraquat tank-mixed with a residual herbicide of metribuzin, pyroxasulfone, saflufenacil, flumioxazin, pyroxasulfone plus flumioxazin, or pyroxasulfone plus fluthiacet improved control of regrowth or new emergence compared with paraquat alone. All residual herbicide treatments provided similar GR Palmer amaranth control. Through implementation of POST-harvest herbicide applications, the addition of 1,200 seed m−2or approximately 12 million seed ha−1to the soil seedbank was prevented. Overall, the addition of a residual herbicide provided only 4 to 7% more GR Palmer amaranth control than paraquat alone. Wheat injury was evident (< 10%) in 2012 from the PRE applications, but not in 2013. Wheat grain yield was not adversely affected by any herbicide application.

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