scholarly journals Control of acetolactate synthase inhibitor/glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in isoxaflutole/glufosinate/glyphosate-resistant soybean

2021 ◽  
pp. 1-23
Author(s):  
Jasmine Mausbach ◽  
Suat Irmak ◽  
Debalin Sarangi ◽  
John Lindquist ◽  
Amit J. Jhala
Keyword(s):  
Field Experiments ◽  
Cropping Systems ◽  
Acetolactate Synthase ◽  
The United States ◽  
Palmer Amaranth ◽  
Effective Control ◽  
Synthase Inhibitor ◽  
Density And Biomass ◽  
Als Inhibitor ◽  
Herbicide Programs

Abstract Palmer amaranth is the most problematic and troublesome weed in agronomic cropping systems in the United States. Acetolactate synthase (ALS) inhibitor- and glyphosate-resistant (GR) Palmer amaranth has been confirmed in Nebraska and it is widespread in several counties. Soybean resistant to isoxaflutole/glufosinate/glyphosate has been developed that provides additional herbicide site of action for control of herbicide-resistant weeds. The objectives of this study were to evaluate herbicide programs for control of ALS inhibitor/GR Palmer amaranth and their effect on Palmer amaranth density and biomass, as well as soybean injury and yield in isoxaflutole/glufosinate/glyphosate-resistant soybean. Field experiments were conducted in a grower’s field infested with ALS inhibitor- and GR Palmer amaranth near Carleton, Nebraska, in 2018 and 2019. Isoxaflutole applied alone or mixed with sulfentrazone/pyroxasulfone, flumioxazin/pyroxasulfone, or imazethapyr/saflufenacil/pyroxasulfone provided similar control (86%-99%) of Palmer amaranth 21 d after PRE (DAPRE). At 14 d after early-POST (DAEPOST), isoxaflutole applied PRE and PRE followed by (fb) POST controlled Palmer amaranth 10% to 63% compared to 75% to 96% control with glufosinate applied EPOST in both years. A PRE herbicide fb glufosinate controlled Palmer amaranth 80% to 99% 21 d after late-POST (DALPOST) in 2018 and reduced density 89% to 100% in 2018 and 58% to 100% in 2019 at 14 DAEPOST. No soybean injury was observed from any of the herbicide programs tested in this study. Soybean yield in 2019 was relatively higher due to higher precipitation compared with 2018 with generally no differences between herbicide programs. This research indicates that herbicide programs are available for effective control of ALS inhibitor/GR Palmer amaranth in isoxaflutole/glufosinate/glyphosate-resistant soybean.

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

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.

Multiple herbicide-resistant Palmer amaranth (Amaranthus palmeri) in Connecticut: confirmation and response to POST herbicides

2021 ◽  
pp. 1-7
Author(s):  
Jatinder S. Aulakh ◽  
Parminder S. Chahal ◽  
Vipan Kumar ◽  
Andrew J. Price ◽  
Karl Guillard
Keyword(s):  
Cropping Systems ◽  
Acetolactate Synthase ◽  
Palmer Amaranth ◽  
Effective Control ◽  
Herbicide Resistant ◽  
First Case ◽  
Whole Plant ◽  
Chlorimuron Ethyl ◽  
Als Inhibitors ◽  
Als Inhibitor

Abstract Palmer amaranth is the latest pigweed species documented in Connecticut; it was identified there in 2019. In a single-dose experiment, the Connecticut Palmer amaranth biotype survived the field-use rates of glyphosate (840 g ae ha−1) and imazaquin (137 g ai ha−1) herbicides applied separately. Additional experiments were conducted to (1) determine the level of resistance to glyphosate and acetolactate synthase (ALS) inhibitors in the Connecticut-resistant (CT-Res) biotype using whole-plant dose-response bioassays, and (2) evaluate the response of the CT-Res biotype to POST herbicides commonly used in Connecticut cropping systems. Based on the effective dose required for 90% control (ED90), the CT-Res biotype was 10-fold resistant to glyphosate when compared with the Kansas-susceptible (KS-Sus) biotype. Furthermore, the CT-Res biotype was highly resistant to ALS-inhibitor herbicides; only 18% control was achieved with 2,196 g ai ha−1 imazaquin. The CT-Res biotype was also cross-resistant to other ALS-inhibitor herbicides, including chlorimuron-ethyl (13.1 g ai ha−1), halosulfuron-methyl (70 g ai ha−1), and sulfometuron-methyl (392 g ai ha−1). The CT-Res Palmer amaranth was controlled 75% to 100% at 21 d after treatment (DAT) with POST applications of 2,4-D (386 g ae ha−1), carfentrazone-ethyl (34 g ai ha−1), clopyralid (280 g ae ha−1), dicamba (280 g ae ha−1), glufosinate (595 g ai ha−1), lactofen (220 g ai ha−1), oxyfluorfen (1,121g ai ha−1), and mesotrione (105 g ai ha−1) herbicides. Atrazine (2,240 g ai ha−1) controlled the CT-Res biotype only 52%, suggesting the biotype is resistant to this herbicide as well. Here we report the first case of Palmer amaranth from Connecticut with multiple resistance to glyphosate and ALS inhibitors. Growers should proactively use all available weed control tactics, including the use of effective PRE and alternative POST herbicides (tested in this study), for effective control of the CT-Res biotype.

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

2013 ◽  
Vol 27 (2) ◽  
pp. 291-297 ◽  
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.

Glyphosate- and acetolactate synthase inhibitor-resistant kochia (Bassia scoparia) control in field pea

2021 ◽  
Author(s):  
Alysha T Torbiak ◽  
Robert Blackshaw ◽  
Randall N Brandt ◽  
Bill Hamman ◽  
Charles M. Geddes
Keyword(s):  
Great Plains ◽  
Field Experiments ◽  
Rapid Evolution ◽  
Acetolactate Synthase ◽  
Field Pea ◽  
Visible Injury ◽  
Crop Harvest ◽  
Selection For ◽  
Synthase Inhibitor ◽  
Als Inhibitor

Kochia [Bassia scoparia (L.) A.J. Scott] is an invasive C4 tumbleweed in the Great Plains of North America, where it impedes crop harvest and causes significant crop yield losses. Rapid evolution and spread of glyphosate- and acetolactate synthase (ALS) inhibitor-resistant kochia in western Canada limit the herbicide options available for control of these biotypes in field pea (Pisum sativum L.); one of the predominant pulse crops grown in this region. Field experiments were conducted near Lethbridge, Alberta in 2013-2015 and Coalhurst, Alberta in 2013-2014 to determine which herbicide options effectively control glyphosate- and ALS inhibitor-resistant kochia in field pea. Visible injury of field pea was minor (0-4%) in all environments except for Lethbridge 2013, where pre-plant (PP) flumioxazin and all treatments containing post-emergence (POST) imazamox/bentazon resulted in unacceptable (14-23%) pea visible injury. Herbicide impacts on pea yield were minor overall. Carfentrazone + sulfentrazone PP and saflufenacil PP followed by imazamox/bentazon POST resulted in ≥80% visible control of kochia in all environments, while POST imazamox/bentazon alone resulted in ≥80% reduction in kochia biomass in all environments compared with the untreated control (albeit absent of statistical difference in Coalhurst 2014). These results suggest that layering the protoporhyrinogen oxidase-inhibiting herbicides saflufenacil or carfentrazone + sulfentrazone PP with the ALS- and photosystem II-inhibiting herbicide combination imazamox/bentazon POST can effectively control glyphosate- and ALS inhibitor-resistant kochia in field pea while also mitigating further selection for herbicide resistance through the use of multiple effective herbicide modes-of-action.

Influence of planting date and herbicide program on Amaranthus palmeri control in dry bean

2021 ◽  
pp. 1-23
Author(s):  
Clint W. Beiermann ◽  
Cody F. Creech ◽  
Stevan Z. Knezevic ◽  
Amit J. Jhala ◽  
Robert Harveson ◽  
...  
Keyword(s):  
Weed Control ◽  
Field Experiments ◽  
Acetolactate Synthase ◽  
Planting Date ◽  
Palmer Amaranth ◽  
Dry Bean ◽  
Control Programs ◽  
Main Plot ◽  
Bean Yield ◽  
Density And Biomass

Abstract Late-emerging summer annual weeds are difficult to control in dry bean production fields. Dry bean is a poor competitor with weeds, due to its slow rate of growth and delayed canopy formation. Palmer amaranth is particularly difficult to control due to season-long emergence and resistance to acetolactate synthase (ALS)-inhibiting herbicides. Dry bean growers rely on PPI and preemergence residual herbicides for the foundation of their weed control programs; however, postemergence herbicides are often needed for season-long weed control. The objective of this experiment was to evaluate effect of planting date and herbicide program on late-season weed control in dry bean in western Nebraska. Field experiments were conducted in 2017 and 2018 near Scottsbluff, Nebraska. The experiment was arranged in a split-plot design, with planting date and herbicide program as main-plot and sub-plot factor, respectively. Delayed planting was represented by a delay of 15 days after standard planting time. The treatments EPTC + ethalfluralin, EPTC + ethalfluralin fb imazamox + bentazon, and pendimethalin + dimethenamid-P fb imazamox + bentazon, resulted in the lowest Palmer amaranth density three weeks after treatment (WAT) and the highest dry bean yield. The imazamox + bentazon treatment provided poor Palmer amaranth control and did not consistently result in Palmer amaranth density and biomass reduction, compared to the non-treated control. In 2018, the delayed planting treatment had reduced Palmer amaranth biomass with the pendimethalin + dimethenamid-P treatment, as compared to standard planting. Delaying planting did not reduce dry bean yield and had limited benefit in improving weed control in dry bean.

scholarly journals Comparison of Herbicide Programs for Season-Long Control of Glyphosate-Resistant Common Waterhemp (Amaranthus rudis) in Soybean

2017 ◽  
Vol 31 (1) ◽  
pp. 53-66 ◽  
Author(s):  
Debalin Sarangi ◽  
Lowell D. Sandell ◽  
Greg R. Kruger ◽  
Stevan Z. Knezevic ◽  
Suat Irmak ◽  
...  
Keyword(s):  
Field Experiments ◽  
Acetolactate Synthase ◽  
Growing Season ◽  
Soybean Field ◽  
Common Waterhemp ◽  
Need To Evaluate ◽  
Amaranthus Rudis ◽  
Reduced Density ◽  
Als Inhibitor ◽  
Herbicide Programs

The evolution of glyphosate and acetolactate synthase (ALS) inhibitor-resistant common waterhemp in the Midwestern United States has reduced the number of effective POST herbicide options for management of this problem weed in glyphosate-resistant soybean. Moreover, common waterhemp emerges throughout the crop growing season, justifying the need to evaluate herbicide programs that provide season-long control. The objectives of this study were to compare POST-only and PRE followed by (fb) POST herbicide programs for control of glyphosate-resistant common waterhemp in glyphosate-resistant soybean. Field experiments were conducted in 2013 and 2014 in Dodge County, NE, in a field infested with glyphosate-resistant common waterhemp. Programs containing PRE herbicides resulted in ≥83% control of common waterhemp and densities of ≤35 plantsm–2at 21 d after PRE (DAPRE). Post-only herbicide programs resulted in <70% control and densities of 107 to 215 plants m–2at 14 d after early-POST (DAEPOST) treatment. PRE fb POST herbicide programs, including saflufenacil plus imazethapyr plus dimethenamid-P, sulfentrazone plus cloransulam, orS-metolachlor plus metribuzin, fb fomesafen plus glyphosate;S-metolachlor plus fomesafen fb acifluorfen plus glyphosate resulted in >90% control of glyphosate-resistant common waterhemp throughout the growing season, reduced density to ≤7plantsm–2, ≥92% biomass reduction, and soybean yield >2,200kg ha–1. Averaged across herbicide programs, common waterhemp control was 84%, and density was 15 plants m–2with PRE fb POST herbicide programs compared with 42% control, and density of 101 plants m–2with POST-only herbicide programs at harvest. Results of this study indicated that PRE fb POST herbicide programs with effective modes of action exist for season-long control of glyphosate-resistant common waterhemp in glyphosate-resistant soybean.

Herbicide Programs for Control of Waterhemp (Amaranthus tuberculatus) Resistant to Three Distinct Herbicide Sites of Action in Corn

2020 ◽  
pp. 1-28
Author(s):  
Christian Willemse ◽  
Nader Soltani ◽  
Lauren Benoit ◽  
David C. Hooker ◽  
Amit J. Jhala ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Trials ◽  
Effective Control ◽  
High Fecundity ◽  
Field Corn ◽  
Amaranthus Tuberculatus ◽  
Excellent Control ◽  
Density And Biomass ◽  
Sites Of Action ◽  
Herbicide Programs

Abstract Control of waterhemp is becoming more difficult in Ontario as biotypes have evolved resistance to four herbicide sites of action (SOA) including groups 2, 5, 9, and 14. The objective of this study was to compare PRE, POST, and PRE followed by (fb) POST herbicide programs and their effect on control, density, and biomass of multiple herbicide-resistant (MHR) waterhemp as well as corn injury and grain yield. Two separate field experiments, each consisting of five field trials, were conducted over a two-year period (2018 and 2019) in corn in Ontario, Canada. The first experiment evaluated MHR waterhemp control with 4-hydroxyphenyl-pyruvate dioxygenase (HPPD) inhibitor containing programs applied PRE, HPPD-inhibitor containing programs applied PRE fb glufosinate applied POST, and glufosinate applied POST. The second experiment evaluated MHR waterhemp control with non-HPPD inhibitor containing programs applied PRE, non-HPPD inhibitor containing programs applied PRE fb atrazine + mesotrione applied POST, and atrazine + mesotrione applied POST. Atrazine + isoxaflutole caused 3 to 5% corn injury at E1; no corn injury was observed with PRE and POST herbicide programs at other environments. In general, atrazine/bicyclopyrone/mesotrione/S-metolachlor and dimethenamid-P/saflufenacil, applied PRE, controlled MHR waterhemp ≥ 95% 12 weeks after POST application (WAA). A POST application of glufosinate following atrazine + tolpyralate PRE, and a POST application of atrazine + mesotrione following atrazine/dicamba or atrazine/S-metolachlor PRE, improved control at 4, 8, and 12 WAA in most environments. In general, PRE fb POST applications resulted in better control of MHR waterhemp throughout the growing season than PRE and POST applications (P<0.05). It is concluded that herbicide programs based on multiple effective SOA are available for effective control of MHR waterhemp in field corn and it is advisable that when choosing a herbicide program, excellent control of MHR waterhemp should be the goal given its high fecundity and competitive ability.

Transfer and Expression of ALS Inhibitor Resistance from Palmer Amaranth (Amaranthus palmeri) to anA. spinosus×A. palmeriHybrid

Weed Science ◽  
2016 ◽  
Vol 64 (2) ◽  
pp. 240-247 ◽  
Author(s):  
William T. Molin ◽  
Vijay K. Nandula ◽  
Alice A. Wright ◽  
Jason A. Bond
Keyword(s):  
Field Experiments ◽  
Acetolactate Synthase ◽  
Palmer Amaranth ◽  
Enzyme Assays ◽  
Amaranthus Palmeri ◽  
Weed Species ◽  
Als Inhibitors ◽  
Inhibitor Resistance ◽  
Als Inhibitor ◽  
Interspecific Transfer

Transfer of herbicide resistance among closely related weed species is a topic of growing concern. A spiny amaranth × Palmer amaranth hybrid was confirmed resistant to several acetolactate synthase (ALS) inhibitors including imazethapyr, nicosulfuron, pyrithiobac, and trifloxysulfuron. Enzyme assays indicated that the ALS enzyme was insensitive to pyrithiobac and sequencing revealed the presence of a known resistance conferring point mutation, Trp574Leu. Alignment of the ALS gene for Palmer amaranth, spiny amaranth, and putative hybrids revealed the presence of Palmer amaranth ALS sequence in the hybrids rather than spiny amaranth ALS sequences. In addition, sequence upstream of the ALS in the hybrids matched Palmer amaranth and not spiny amaranth. The potential for transfer of ALS inhibitor resistance by hybridization has been demonstrated in the greenhouse and in field experiments. This is the first report of gene transfer for ALS inhibitor resistance documented to occur in the field without artificial/human intervention. These results highlight the need to control related species in both field and surrounding noncrop areas to avoid interspecific transfer of resistance genes.

A Survey for Diclofop-Methyl Resistance in Italian Ryegrass from Tennessee and How To Manage Resistance in Wheat

2010 ◽  
Vol 24 (3) ◽  
pp. 303-309 ◽  
Author(s):  
Andrew T. Ellis ◽  
Lawrence E. Steckel ◽  
Christopher L. Main ◽  
Marcel S. C. De Melo ◽  
Dennis R. West ◽  
...  
Keyword(s):  
Field Experiments ◽  
Wheat Yield ◽  
Acetolactate Synthase ◽  
The United States ◽  
Research Field ◽  
Italian Ryegrass ◽  
Cross Resistance ◽  
Susceptible Population ◽  
Application Timing ◽  
Herbicide Programs

Italian ryegrass resistance to diclofop has been documented in several countries, including the United States. The purpose of this research was to screen selected putative resistant populations of Italian ryegrass for resistance to the acetyl-CoA carboxylase (ACCase)–inhibiting herbicides diclofop and pinoxaden and the acetolactate synthase (ALS)–inhibiting herbicides imazamox, pyroxsulam, and mesosulfuron in the greenhouse and to use field experiments to develop herbicide programs for Italian ryegrass control. Resistance to diclofop was confirmed in eight populations from Tennessee. These eight populations did not show cross-resistance to pinoxaden. One additional population (R1) from Union County, North Carolina, was found to be resistant to both diclofop and pinoxaden. The level of resistance to pinoxaden of the R1 population was 15 times that of the susceptible population. No resistance was confirmed to any of the ALS-inhibiting herbicides examined in this research. Field experiments demonstrated PRE Italian ryegrass control with chlorsulfuron (71 to 94%) and flufenacet + metribuzin (84 to 96%). Italian ryegrass control with pendimethalin applied PRE or delayed preemergence (DPRE) was variable (0 to 85%). POST control of Italian ryegrass was acceptable with pinoxaden, mesosulfuron, flufenacet + metribuzin, and chlorsulfuron + flucarbazone (> 80%). Application timing and herbicide treatment had no effect on wheat yield, except for diclofop and pendimethalin treatments, in which uncontrolled Italian ryegrass reduced wheat yield.

scholarly journals Effect of row spacing and herbicide programs for control of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in dicamba/glyphosate-resistant soybean

2021 ◽  
pp. 1-41
Author(s):  
Shawn T. McDonald ◽  
Adam Striegel ◽  
Parminder S. Chahal ◽  
Prashant Jha ◽  
Jennifer M. Rees ◽  
...  
Keyword(s):  
Field Experiments ◽  
Cultural Practices ◽  
Integrated Approach ◽  
The United States ◽  
Palmer Amaranth ◽  
Row Spacing ◽  
Soybean Field ◽  
Narrow Row ◽  
Herbicide Programs ◽  
Uniform Population

Abstract Glyphosate-resistant (GR) Palmer amaranth is one of the most difficult to control weeds in soybean production fields in Nebraska and the United States. An integrated approach is required for effective management of GR Palmer amaranth. Cultural practices such as narrow row spacing might augment herbicide efficacy for management of GR Palmer amaranth. The objectives of this study were to evaluate the effect of row spacing and herbicide programs for management of GR Palmer amaranth in dicamba/glyphosate-resistant (DGR) soybean. Field experiments were conducted in a grower’s field with a uniform population of GR Palmer amaranth near Carleton, Nebraska in 2018 and 2019. Year-by-herbicide program-by-row spacing interactions were significant for all variables; therefore, data were analyzed by year. Herbicides applied preemergence (PRE) controlled GR Palmer amaranth ≥ 95% in both years 14 d after PRE (DAPRE). Across soybean row-spacing, most PRE fb early-POST (EPOST) herbicide programs provided 84% to 97% control of Palmer amaranth compared with most EPOST fb late-post (LPOST) programs, excluding dicamba in single and sequential applications (82% to 95% control). Mixing microencapsulated acetochlor with a POST herbicide in PRE fb EPOST herbicide programs controlled Palmer amaranth ≥ 93% 14 DAEPOST and ≥ 96% 21 DALPOST with no effect on Palmer amaranth density. Interaction of herbicide program-by-row spacing on Palmer amaranth control was not significant; however, biomass reduction was significant at soybean harvest in 2019. The herbicide programs evaluated in this study caused no soybean injury. Due to drought conditions during a majority of the 2018 growing season, soybean yield in 2018 was reduced compared to 2019.

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