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

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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Seed Retention of Palmer amaranth (Amaranthus palmeri) and Barnyardgrass (Echinochloa crus-galli) in Soybean

Weed Technology ◽

10.1017/wet.2017.25 ◽

2017 ◽

Vol 31 (4) ◽

pp. 617-622 ◽

Cited By ~ 12

Author(s):

Lauren M. Schwartz-Lazaro ◽

Jeremy K. Green ◽

Jason K. Norsworthy

Keyword(s):

Weed Management ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Weed Seed ◽

Weed Species ◽

Seed Retention ◽

The Us ◽

Amaranth Seed ◽

Soil Seedbank ◽

Crop Harvest

Harvest weed seed control is an alternative non-chemical approach to weed management that targets escaped weed seeds at the time of crop harvest. Relatively little is known on how these methods will work on species in the US. Two of the most prominent weeds in soybean production in the midsouthern US are Palmer amaranth and barnyardgrass. Typically, when crop harvesting occurs the weed seed has already either shattered or is taken into the combine and may be redistributed in the soil seedbank. This causes further weed seed spread and may contribute to the addition of resistant seeds in the seedbank. There is little research on how much seed is retained on different weed species at or beyond harvest time. Thus, the objective of this study was to determine the percentage of total Palmer amaranth and barnyardgrass seed production that was retained on the plant during delayed soybean harvest. Retained seed over time was similar between 2015 and 2016, but was significantly different between years for only Palmer amaranth. Seed retention did not differ between years for either weed species. Palmer amaranth and barnyardgrass retained 98 and 41% of their seed at soybean maturity and 95 and 32% of their seed one month after soybean maturity, respectively. Thus, this research indicates that if there are escaped Palmer amaranth plants and soybean is harvested in a timely manner, most seed will enter the combine and offer potential for capture or destruction of these seeds using harvest weed seed control tactics. While there would be some benefit to using HWSC for barnyardgrass, the utility of this practice on mitigating herbicide resistance would be less pronounced than that of Palmer amaranth because of the reduced seed retention or early seed shatter.

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Herbicide-Based Weed Management Programs for Palmer Amaranth (Amaranthus palmeri) in Sweetpotato

Weed Technology ◽

10.1614/wt-d-12-00036.1 ◽

2013 ◽

Vol 27 (2) ◽

pp. 331-340 ◽

Cited By ~ 18

Author(s):

Stephen L. Meyers ◽

Katherine M. Jennings ◽

David W. Monks

Keyword(s):

Weed Management ◽

Palmer Amaranth ◽

Management Systems ◽

Amaranthus Palmeri ◽

Herbicide Application ◽

Crop Tolerance ◽

Hand Weeding

Studies were conducted in 2010 and 2011 to determine the effect of herbicide-based Palmer amaranth management systems in ‘Covington' sweetpotato. Treatments consisted of three herbicide application times. Pretransplant applications were flumioxazin at 107 g ai ha−1, fomesafen at 280 g ai ha−1, flumioxazin at 70 g ha−1plus pyroxasulfone at 89 g ai ha−1, or no herbicide. A second herbicide application was applied within 1 d after transplanting (DAP) and consisted ofS-metolachlor at 800 g ai ha−1, clomazone at 630 g ai ha−1, or no herbicide. Two weeks after planting (WAP) plots receivedS-metolachlor at 800 g ha−1, metribuzin at 140 g ai ha−1, a tank mix ofS-metolachlor at 800 g ha−1plus metribuzin at 140 g ha−1, hand-weeding followed by (fb)S-metolachlor at 800 g ha−1, or no herbicide. Crop tolerance, Palmer amaranth control, and sweetpotato yield in systems containing fomesafen pretransplant were similar to flumioxazin-containing systems. Systems containing flumioxazin plus pyroxasulfone pretransplant resulted in increased crop stunting and decreased sweetpotato yield in 2010, compared with systems containing flumioxazin or fomesafen, but were similar to systems with flumioxazin or fomesafen in 2011. In 2010, systems containingS-metolachlor applied within 1 DAP resulted in increased sweetpotato injury, similar Palmer amaranth control, and reduced no. 1, jumbo, and total sweetpotato yield, compared with systems with clomazone. In 2011, systems containing clomazone were more injurious to sweetpotato than systems receivingS-metolachlor, but Palmer amaranth control and sweetpotato yield were similar. Systems containing metribuzin 2 WAP resulted in increased sweetpotato injury and Palmer amaranth control (in 2010) but similar no. 1 and total sweetpotato yields, compared with systems containingS-metolachlor at 2 WAP. Hand-weeding fbS-metolachlor provided greater Palmer amaranth control and no. 1 sweetpotato yield than did systems ofS-metolachlor without a preceding hand-weeding event in 2010.

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

Weed Technology ◽

10.1017/wet.2021.1 ◽

2021 ◽

pp. 1-9

Author(s):

Clint W. Beiermann ◽

Cody F. Creech ◽

Stevan Z. Knezevic ◽

Amit J. Jhala ◽

Robert Harveson ◽

...

Keyword(s):

Mortality Rates ◽

Selectivity Index ◽

Palmer Amaranth ◽

Greenhouse Experiment ◽

Amaranthus Palmeri ◽

True Leaf ◽

Cotyledon Stage ◽

Equivalent Rate ◽

Herbicide Treatments ◽

High Level

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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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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Effect of tillage on timing ofSetariaspp. emergence and growth

Weed Science ◽

10.1017/s0043174500092274 ◽

1999 ◽

Vol 47 (5) ◽

pp. 563-570 ◽

Cited By ~ 6

Author(s):

Lizabeth A. B. Stahl ◽

Gregg A. Johnson ◽

Ronald L. Wyse ◽

Douglas D. Buhler ◽

Jeffrey L. Gunsolus

Keyword(s):

Seed Production ◽

Weed Management ◽

Cropping Systems ◽

Field Research ◽

Herbicide Application ◽

Tillage Systems ◽

Early Application ◽

Setaria Faberi ◽

Tillage System ◽

Soil Seedbank

Weed management can be a significant challenge in cropping systems, partly because the effects of tillage systems on weed seedbank and seedling population dynamics are not well understood. Field research was conducted from 1994 to 1996 in established tillage plots consisting of moldboard plow (MP), chisel plow (CP), and no-tillage (NT). The objectives were to determine the effects of long-term tillage systems on the timing and duration ofSetariaspp. emergence and percentage cumulative emergence from the soil seedbank and to investigate the effect of tillage onSetariaspp. density and seed production following glyphosate application atSetariaspp. heights of 5, 10, and 15 cm. NT contained a greater number ofSetariaspp. seed in the 0- to 1-, 1- to 3-, and 3- to 6-cm depths than MP or CP systems. There was little difference between the three tillage systems at depths greater than 6 cm.Setariaspp. emergence was greater in NT than in MP or CP in 1994 and 1996 and greater than in MP in 1995. There was a substantial increase inSetariaspp. emergence in NT between 3 and 4 weeks after planting (WAP) in 1994 and between 5 and 6 WAP in 1995 and 1996. Significant emergence did not occur past 5 to 6 WAP in 1994 and 1995 but continued over a longer period of time in 1996.Setariaspp. plants consistently reached targeted herbicide application heights 4 to 9 d earlier in NT than in CP and MP. In 1994, finalSetariaspp. density was greater in NT compared to CP and MP at the 5- and 10-cm herbicide application timings. When glyphosate was applied to 15-cm-tallSetaria, very few weeds were present following application across all tillage systems. In 1995, NT resulted in greaterSetariaspp. density than MP or CP across all application timings. There was no difference in finalSetariaspp. density between MP and CP across all glyphosate timings in 1994 and 1995. Seed production was negligible in MP and CP, regardless of glyphosate timing. In NT, however, significant seed production occurred, especially with early application. Results indicate that the effectiveness of nonresidual herbicides forSetaria faberiHerrm. control is influenced by tillage system and the timing of application.

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Using the Rosette Technique for Canada Thistle (Cirsium arvense) Control in Row Crops

Weed Technology ◽

10.1017/s0890037x00044572 ◽

1998 ◽

Vol 12 (4) ◽

pp. 699-706 ◽

Cited By ~ 5

Author(s):

Brett R. Miller ◽

Rodney G. Lym

Keyword(s):

Weed Management ◽

Crop Production ◽

Management Program ◽

Cirsium Arvense ◽

Herbicide Application ◽

Canada Thistle ◽

Row Crops ◽

Row Crop ◽

Herbicide Treatments ◽

Standard Practices

Clopyralid applied to Canada thistle rosettes has provided better control in the following growing season than applications to bolted plants. The objectives of this research were to determine if using cultivation to prevent plants from bolting prior to herbicide application (the rosette technique) could be successfully incorporated into a row crop production system and to evaluate the effect of Canada thistle growth stage on the absorption and translocation of14C-clopyralid. Canada thistle control 8 mo after postharvest herbicide treatment (MAFT) using the rosette technique was similar to control when using conventional in-crop plus postharvest herbicide treatments in corn and soybean. Glyphosate and clopyralid plus 2,4-D were the most consistent postharvest herbicide treatments for Canada thistle control 8 MAFT in corn and soybean. Corn yields were similar, but soybean yields were slightly lower when Canada thistle was controlled using cultivation compared to conventional herbicide treatments.14C-clopyralid translocation to Canada thistle roots and lower shoot parts was greater when clopyralid was applied to the rosette stage than when applied to bolted Canada thistle plants. The increased translocation probably accounts for the increased Canada thistle control observed in the field. Incorporating the rosette technique into a weed management program should allow growers to control Canada thistle with less herbicide input than do standard practices.

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Weed Management in Corn with Postemergence Applications of Tembotrione or Thiencarbazone : Tembotrione

Weed Technology ◽

10.1614/wt-d-14-00104.1 ◽

2015 ◽

Vol 29 (3) ◽

pp. 350-358 ◽

Cited By ~ 12

Author(s):

Daniel O. Stephenson ◽

Jason A. Bond ◽

Randall L. Landry ◽

H. Matthew Edwards

Keyword(s):

Weed Control ◽

Weed Management ◽

Growth Stage ◽

Field Experiments ◽

Palmer Amaranth ◽

Corn Yield ◽

Herbicide Treatments

Four field experiments were conducted in Louisiana and Mississippi in 2009 and 2010 to evaluate POST herbicides treatments with tembotrione applied alone or as a prepackaged mixture with thiencarbazone for weed control in corn. Treatments included tembotrione at 92 g ai ha−1, thiencarbazone : tembotrione at 15 : 76 g ai ha−1, atrazine at 2,240 g ai ha−1, glufosinate at 450 g ai ha−1, glyphosate at 860 g ae ha−1, and coapplications of tembotrione or thiencarbazone : tembotrione with atrazine, glufosinate, or glyphosate. All treatments were applied to 26-cm corn in the V4 growth stage. Treatments containing thiencarbazone : tembotrione and those with tembotrione controlled barnyardgrass, browntop millet, entireleaf morningglory, hophornbeam copperleaf, johnsongrass, Palmer amaranth, and velvetleaf 85 to 96% and 43 to 97% 28 d after treatment and at corn harvest, respectively. Corn yield ranged from 9,200 to 10,420 kg ha−1and was greater than the nontreated control following all herbicide treatments, except atrazine alone. Results indicated that thiencarbazone : tembotrione or tembotrione POST is an option for weed management in corn, and applications of thiencarbazone : tembotrione would be strongly encouraged where rhizomatous johnsongrass is problematic.

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Impact of Weed Management on Peanut Yield and Weed Populations the Following Year

Peanut Science ◽

10.3146/ps19-9.1 ◽

2019 ◽

Vol 46 (2) ◽

pp. 182-190

Author(s):

A.T. Hare ◽

D.L. Jordan ◽

R.G. Leon ◽

K.L. Edmisten ◽

A.R. Post ◽

...

Keyword(s):

Weed Management ◽

Field Studies ◽

Palmer Amaranth ◽

Herbicide Application ◽

Economic Return ◽

Common Ragweed ◽

Arachis Hypogaea L ◽

Previous Season ◽

Rotational Crop ◽

The Impact

ABSTRACT Field studies were conducted in 2016 and 2017 at two locations in North Carolina to evaluate common ragweed (Ambrosia artemiisifolia L.) (Lewiston-Woodville) and Palmer amaranth (Amanthus palmeri S. Wats) control (Rocky Mount), peanut (Arachis hypogaea L.) yield, and estimated economic return when herbicides were applied postemergence (POST) at 2 or 6 weeks after planting (WAP); 2 and 4 WAP; 4 and 6 WAP; and 2, 4, and 6 WAP. During the following growing season, cotton (Gossypium hirsutum L.) was planted directly into the same plots to determine the impact of weed management during the previous season on weed density. In absence of herbicides, peanut yield was 880 and 1110 kg/ha at Lewiston-Woodville and Rocky Mount, respectively. When weed control depended on a single herbicide application, yield ranged from 1760 to 2660 kg/ha at Lewiston-Woodville, and 2080 to 2480 kg/ha at Rocky Mount. When herbicides were applied twice, peanut yield ranged from 2690 to 3280 kg/ha at Lewiston-Woodville and 3420 to 3840 kg/ha at Rocky Mount. The greatest yields were recorded when herbicides were applied two or three times. Applying herbicides increased the estimated economic return of peanut compared to the non-treated control (NTC). In cotton the following year, common ragweed populations at Lewiston-Woodville were greater following the NTC or a single herbicide application 2 WAP compared to more intensive herbicide programs. Palmer amaranth density at Rocky Mount the following year in cotton was not affected by weed management the previous year in peanut. These results illustrate the relative importance of timing and duration of weed management for peanut and how they influence weed emergence in the following cotton rotational crop.

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