Response of Palmer amaranth (Amaranthus palmeri S. Watson) and sugarbeet to desmedipham and phenmedipham

Abstract A prepackaged mixture of desmedipham + phenmedipham was previously labeled for control of Amaranthus spp. in sugarbeet. Currently, there are no effective POST herbicide options to control glyphosate-resistant Palmer amaranth in sugarbeet. Sugarbeet growers are interested in using desmedipham + phenmedipham to control escaped Palmer amaranth. In 2019, a greenhouse experiment was initiated near Scottsbluff, NE, to determine the selectivity of desmedipham and phenmedipham between Palmer amaranth and sugarbeet. Three populations of Palmer amaranth and four sugarbeet hybrids were evaluated. Herbicide treatments consisted of desmedipham and phenmedipham applied singly or as mixtures at an equivalent rate. Herbicides were applied when Palmer amaranth and sugarbeet were at the cotyledon stage, or two true-leaf sugarbeet stage and when Palmer amaranth was 7 cm tall. The selectivity indices for desmedipham, phenmedipham, and desmedipham + phenmedipham were 1.61, 2.47, and 3.05, respectively, at the cotyledon stage. At the two true-leaf application stage, the highest rates of desmedipham and phenmedipham were associated with low mortality rates in sugarbeet, resulting in a failed response of death. The highest rates of desmedipham + phenmedipham caused a death response of sugarbeet; the selectivity index was 2.15. Desmedipham treatments resulted in lower LD50 estimates for Palmer amaranth compared to phenmedipham, indicating that desmedipham can provide greater levels of control for Palmer amaranth. However, desmedipham also caused greater injury in sugarbeet, producing lower LD50 estimates compared to phenmedipham. Desmedipham + phenmedipham provided 90% or greater control of cotyledon-size Palmer amaranth at a labeled rate but also caused high levels of sugarbeet injury. Neither desmedipham, phenmedipham, nor desmedipham + phenmedipham was able to control 7-cm tall Palmer amaranth at previously labeled rates. Results indicate that desmedipham + phenmedipham can only control Palmer amaranth if applied at the cotyledon stage and a high level of sugarbeet injury is acceptable.

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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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Evaluation of Herbicide Programs for Use in a 2,4-D–Resistant Soybean Technology for Control of Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri)

Weed Technology ◽

10.1614/wt-d-15-00129.1 ◽

2016 ◽

Vol 30 (2) ◽

pp. 366-376 ◽

Cited By ~ 11

Author(s):

M. Ryan Miller ◽

Jason K. Norsworthy

Keyword(s):

Weed Management ◽

Field Experiments ◽

Palmer Amaranth ◽

Integrated Weed Management ◽

Amaranthus Palmeri ◽

Early Season ◽

Fully Integrated ◽

Soil Seedbank ◽

High Level ◽

Herbicide Programs

Two separate field experiments were conducted over a 2-yr period in Fayetteville, AR, during 2012 and 2013 to (1) evaluate POST herbicide programs utilizing a premixture of dimethylamine (DMA) salt of glyphosate + choline salt of 2,4-D in a soybean line resistant to 2,4-D, glyphosate, and glufosinate and (2) determine efficacy of herbicide programs that begin with PRE residual herbicides followed by POST applications of 2,4-D choline + glyphosate DMA on glyphosate-resistant Palmer amaranth. In the first experiment, POST applications alone that incorporated the use of residual herbicides with the glyphosate + 2,4-D premixture provided 93 to 99% control of Palmer amaranth at the end of the season. In the second experiment, the use of flumioxazin, flumioxazin + chlorimuron methyl, S-metolachlor + fomesafen, or sulfentrazone + chloransulam applied PRE provided 94 to 98% early-season Palmer amaranth control. Early-season control helped maintain a high level of Palmer amaranth control throughout the growing season, in turn resulting in fewer reproductive Palmer amaranth plants present at soybean harvest compared to most other treatments. Although no differences in soybean yield were observed among treated plots, it was evident that herbicide programs should begin with PRE residual herbicides followed by POST applications of glyphosate + 2,4-D mixed with residual herbicides to minimize late-season escapes and reduce the likelihood of contributions to the soil seedbank. Dependent upon management decisions, the best stewardship of this technology will likely rely on the use multiple effective mechanisms of action incorporated into a fully integrated weed management system.

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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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Rapid detoxification via glutathioneS-transferase (GST) conjugation confers a high level of atrazine resistance in Palmer amaranth (Amaranthus palmeri)

Pest Management Science ◽

10.1002/ps.4615 ◽

2017 ◽

Vol 73 (11) ◽

pp. 2236-2243 ◽

Cited By ~ 28

Author(s):

Sridevi Nakka ◽

Amar S Godar ◽

Curtis R Thompson ◽

Dallas E Peterson ◽

Mithila Jugulam

Keyword(s):

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Atrazine Resistance ◽

High Level

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Effect of PPO-Inhibiting Herbicides on the Growth and Sex Ratio of a Dioecious Weed Species Amaranthus palmeri (Palmer Amaranth)

Agronomy ◽

10.3390/agronomy9060275 ◽

2019 ◽

Vol 9 (6) ◽

pp. 275 ◽

Cited By ~ 1

Author(s):

Mafia M. Rumpa ◽

Ronald F. Krausz ◽

David J. Gibson ◽

Karla L. Gage

Keyword(s):

Sex Ratio ◽

Seed Production ◽

Sex Ratios ◽

Rapid Evolution ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Weed Species ◽

Herbicide Treatments ◽

Underlying Mechanisms ◽

Sites Of Action

Amaranthus palmeri S. Watson (Palmer amaranth) is a fast-growing, dioecious, highly competitive agricultural weed species, which is spreading across the US Midwest. Population sex ratios are an important consideration in the management of A. palmeri populations as this species has become resistant to several herbicide sites of action, and there is need to minimize seed production by female plants. Environmental conditions, particularly stressors, may influence sex ratios, and herbicides act as major stressors and evolutionary filters in agricultural fields. Amaranthus spp. have shown a tendency for rapid evolution of herbicide resistance, with the frequency of protoporphyrinogen oxidase (PPO)-inhibitor resistance increasing across the Midwestern US. A greenhouse experiment was conducted to investigate the effect of two PPO-inhibiting herbicide treatments of either lactofen or fomesafen on four different Illinois populations (Cahokia, Collinsville, Rend Lake, and Massac). Plants raised from seed from the Massac population were tallest, and both males and females from this population also had the highest vegetative biomass. Female plants from the Collinsville population had more reproductive biomass than male plants. Control populations were male-biased (Cahokia, Collinsville), female-biased (Masaac), and 1:1 (Rend Lake). Lactofen shifted the male-biased populations to female-biased or 1:1 and the female-biased population to 1:1. Fomesafen-treated populations were male-biased or 1:1. This study suggests that PPO-inhibiting herbicide treatments may influence the growth and sex ratio of A. palmeri populations, which is an underlying factor in the rate of herbicide evolution in this species. An understanding of the underlying mechanisms of how external factors influence sex ratios may eventually provide an opportunity to reduce seed production in populations by shifting sex ratios towards a male bias.

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Weed Control and Peanut Tolerance with Ethalfluralin-Based Herbicide Systems

International Journal of Agronomy ◽

10.1155/2012/597434 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

W. J. Grichar ◽

P. A. Dotray

Keyword(s):

Weed Control ◽

Arachis Hypogaea ◽

Field Studies ◽

Palmer Amaranth ◽

Tribulus Terrestris ◽

Amaranthus Palmeri ◽

Cyperus Esculentus ◽

Yellow Nutsedge ◽

Devil’S Claw ◽

Herbicide Treatments

Field studies were conducted from 2007 through 2009 to determine weed efficacy and peanut (Arachis hypogaeaL.) response to herbicide systems that included ethalfluralin applied preplant incorporated. Control of devil's claw (Proboscidea louisianica(Mill.) Thellung), yellow nutsedge (Cyperus esculentusL.), Palmer amaranth (Amaranthus palmeriS. Wats.), and puncturevine (Tribulus terrestrisL.) was most consistent with ethalfluralin followed by either imazapic or imazethapyr applied postemergence. Peanut stunting was 19% when paraquat alone was applied early-postemergence. Stunting increased to greater than 30% when ethalfluralin applied preplant incorporated was followed byS-metolachlor applied preemergence and paraquat applied early-postemergence. Stunting (7%) was also observed when ethalfluralin was followed by flumioxazin plusS-metolachlor applied preemergence with lactofen applied mid-postemergence. Ethalfluralin followed by paraquat applied early-postemergence reduced peanut yield when compared to the nontreated check. Ethalfluralin applied preplant incorporated followed by imazapic applied mid-postemergence provided the greatest yield (6220 kg/ha). None of the herbicide treatments reduced peanut grade (sound mature kernels plus sound splits) when compared with the nontreated check.

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Evaluation of Early-Season and Postharvest Herbicide Treatments on Alfalfa (Medicago sativa)

Weed Science ◽

10.1017/s0043174500083132 ◽

1985 ◽

Vol 33 (5) ◽

pp. 708-713 ◽

Cited By ~ 1

Author(s):

Kimberly T. Winton ◽

Jimmy F. Stritzke

Keyword(s):

Medicago Sativa ◽

Palmer Amaranth ◽

Yield Reduction ◽

Amaranthus Palmeri ◽

Early Season ◽

Tolerance Level ◽

Herbicide Treatments ◽

Residue Levels ◽

Forage Yields

Terbacil (3-tert-butyl-5-chloro-6-methyluracil), diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione], and metribuzin [4-amino-6-butyl-3-(methylthio)-as-triazin-5(4H)-one] controlled palmer amaranth (Amaranthus palmeriS. Wats. ♯ AMAPA) in established alfalfa (Medicago sativaL.) when applied after first harvest. However, these same herbicides did not control palmer amaranth when applied early-season in March. Alfalfa forage yields were increased when palmer amaranth was controlled. Residue levels of terbacil and its metabolites in alfalfa forage from plots treated postharvest with 1.1 kg/ha of terbacil were well below the 5-ppm tolerance level established for terbacil in alfalfa. There was some chlorosis of alfalfa foliage following the postharvest use of the 1.1 kg ai/ha of terbacil. There was also a yield reduction of alfalfa in two of the six experiments (one from a March and one from a June application) where 1.1 kg ai/ha of terbacil was evaluated.

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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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Efficacy of residual herbicides influenced by cover-crop residue for control of Amaranthus palmeri and A. tuberculatus in soybean

Weed Technology ◽

10.1017/wet.2020.77 ◽

2020 ◽

pp. 1-5

Author(s):

Clay M. Perkins ◽

Karla L. Gage ◽

Jason K. Norsworthy ◽

Bryan G. Young ◽

Kevin W. Bradley ◽

...

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Crop Residue ◽

Field Studies ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Cereal Rye ◽

No Till ◽

Herbicide Treatments ◽

Residual Control

Abstract Field studies were conducted in 2018 and 2019 in Arkansas, Indiana, Illinois, Missouri, and Tennessee to determine if cover-crop residue interfered with herbicides that provide residual control of Palmer amaranth and waterhemp in no-till soybean. The experiments were established in the fall with planting of cover crops (cereal rye + hairy vetch). Herbicide treatments consisted of a nontreated or no residual, acetochlor, dimethenamid-P, flumioxazin, pyroxasulfone + flumioxazin, pendimethalin, metribuzin, pyroxasulfone, and S-metolachlor. Palmer amaranth took 18 d and waterhemp took 24 d in the cover crop–alone (nontreated) treatment to reach a height of 10 cm. Compared with this treatment, all herbicides except metribuzin increased the number of days until 10-cm Palmer amaranth was present. Flumioxazin applied alone or in a mixture with pyroxasulfone were the best at delaying Palmer amaranth growing to a height of 10 cm (35 d and 33 d, respectively). The herbicides that resulted in the lowest Palmer amaranth density (1.5 to 4 times less) integrated with a cover crop were pyroxasulfone + flumioxazin, flumioxazin, pyroxasulfone, and acetochlor. Those four herbicide treatments also delayed Palmer amaranth emergence for the longest period (27 to 34 d). Waterhemp density was 7 to 14 times less with acetochlor than all the other herbicides present. Yield differences were observed for locations with waterhemp. This research supports previous research indicating that utilizing soil-residual herbicides along with cover crops improves control of Palmer amaranth and/or waterhemp.

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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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