**2. Materials and methods**

Traditional corn and cotton weed management programs have relied on PRE applications of a broadleaf and grass herbicide for residual season‐long weed control [36–41]. In corn, these PRE programs usually have included atrazine in combination for broad‐spectrum weed con‐ trol. Atrazine is used in over 60% of the USA corn, and its doses have gotten lower with most doses of no more than 1.12 kg ha−1 with some growers applying no more than 0.84 kg ha−1 [42]. Atrazine and 4‐hydroxylphenylpyruvate dioxygenase (HPPD)‐inhibiting herbicides are commonly used for weed control in corn and are effective in controlling glyphosate‐resistant weeds, including Palmer amaranth [36, 43, 44]. Atrazine can be applied PRE or POST alone or

Since POST herbicides are applied after the weed species and severity are known, this allows growers to assess the problem before making a herbicide application; therefore, POST herbi‐ cides are an essential component of an integrated weed management system to combat the herbicide‐resistant weeds [45]. In addition, POST herbicides typically do not require rainfall for herbicide activation, making performance less dependent on environmental conditions [45]. Also, POST herbicides can reduce the potential for water pollution [46]. A Minnesota study showed reduced atrazine concentrations in runoff water when applied POST compared with soil‐applied applications because of the increased plant residue and cover, limiting the

Two new herbicide systems have recently become important in POST weed control in cotton [48–53]. Dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) is synthetic auxin herbicide that controls glyphosate‐resistant Palmer amaranth and other broadleaf weeds alone or in sequential combina‐ tions with glyphosate or glufosinate [48]. An enzyme, dicamba O‐demethylase, was discovered in a soil bacterium (*Pseudomonas maltophilia*) that converts dicamba to 3,6‐dichlorosalicylic acid (DCSA) [49]. The enzyme DCSA has no significant herbicidal properties. The gene responsible for this enzyme is known as DMO (dicamba monooxygenase). This gene was successfully inserted into mouse‐ear cress [*Arabidopsis thaliana (L). Heynh*.], tomato (*Solanum lycopersicum* L.), and tobacco (*Nicotiana tabacum* L.) and showed to provide these plants with effective tolerance to foliar applications of dicamba [49]. Dicamba‐tolerant cotton, coupled with existing glyphosate‐ and glu‐ fosinate‐tolerant traits, was deregulated in the USA in 2015 and has since become significant por‐ tion of the cotton planted in the USA, comprising over 40% of the crop planted in 2016 [50, 51].

Enlist Duo herbicide, a premix formulation containing 195 g ae L−1 of 2,4‐D choline and 205 g ae L−1 of glyphosate dimethylamine, was developed for use in Enlist corn, cotton, and soy‐ bean. Resistance to 2,4‐D is conferred by the insertion of a gene that codes for the enzyme ary‐ loxyalkanoate dioxygenase. Plants transformed to include this gene can metabolize 2,4‐D to a nonlethal form [52]. Developed during World War II, 2,4‐D was the first selective herbicide widely used in agriculture [53]. Since that time, researchers have demonstrated control of a

The adoption of 2,4‐D in Enlist crops will be influenced by yield potential of the crop, weed species infesting fields, and, most notably, the ability of growers to mitigate off‐target movement of 2,4‐D [58–60]. Although Enlist cotton is resistant to 2,4‐D [61], all other cotton cultivars, including cotton resistant to dicamba, are extremely sensitive to the herbicide, with reports of cotton injury due to 2,4‐D drift dating back to the time of development [62]. Multiple

large number of dicotyledonous weed species with 2,4‐D [54–57].

in tank‐mixtures with several herbicides [16].

66 Herbicide Resistance in Weeds and Crops

amount of herbicide reaching the soil [47].

## **2.1. Corn PRE studies in central and south Texas**

These studies were conducted during the 2013 through 2015 growing season in central Texas near Taylor (30.5326° N, 97.4548° W) and in south‐central Texas near Ganado (29.0438° N, 96.4849° W). Study sites were located in different fields within the same general area of each year. Soils at the Taylor location were a Burleson clay (fine, montmorillonitic, and thermic Udic Pellusterts) with less than 1% organic matter and 7.6 pH, while soils at the Ganado loca‐ tion were a Houston Black clay (fine, montmorillonitic, and thermic Udic Pellusterts) with less than 1% organic matter and 7.4 pH.

Studies were arranged in a randomized complete block design with three replicates. Plot dimensions were two or four corn rows, wide spaced 76–97 cm apart, and 6.3 or 7.9 m long (depending on location). The corn hybrids BH 8846RR (2013), BH 8844VTTP (2014), and BH 8475SS (2015) were planted mid‐ to late February near Taylor and late February to early March near Ganado in each year to a depth of 2.5–3.5 cm at the rate of 54,000–65,500 seeds ha−1.

Herbicides were applied within 5–7 days after planting with a CO<sup>2</sup> ‐pressurized backpack sprayer with TeeJet 11002 flat‐fan nozzles (Spraying Systems Co., North Avenue and Schmale Road, Wheaton, IL 60188) using a pressure of 180 kPa and calibrated to deliver 140 or 187 L ha−1 (depending on location). An untreated check was included for comparison at each location. All herbicide doses were based on the USA label dose with the exception of the acetochlor (74.8% formulation) dose which was applied at 2X of the labeled rate throughout the study by mis‐ take. Once the error was realized, it was decided to maintain this dose throughout the study.

Weed populations varied from year to year and were from naturally occurring soil seed bank populations. At the Taylor location, browntop panicum [*Panicum fasciculatum* Sw. var. *reticulatum* (Torr.) Beal] populations in 2013 were moderate (3–4 plants/m<sup>2</sup> ), while in 2014 populations were higher (6–8 plants/m<sup>2</sup> ). Common barnyardgrass [*Echinochloa crus‐galli* (L.) P. Beauv.] populations in 2015 ranged from 4–8 plants/m<sup>2</sup> . At Ganado, Texas millet [*Urochloa texana* (Buckley) R. Webster] populations ranged from 6–10 plants/m<sup>2</sup> . Palmer amaranth pop‐ ulations varied from 4–8 plants/m<sup>2</sup> at the Taylor location to 2–10 plants/m<sup>2</sup> at the Ganado location. Hophornbeam copperleaf (*Acalypha ostryifolia* Riddell) populations at Taylor in both years were low to moderate (2–6 plants/m<sup>2</sup> ), while common sunflower (*Helianthus annuus* L.) populations ranged from 2–6 plants/m<sup>2</sup> depending on the year.

Crop injury and weed control were estimated visually on a scale of 0–100 (0 indicating no control or injury and 100 indicating complete control or plant death). Crop injury consisted of plant stunting and early season (30 days after herbicide application) and late season (95–140 days after application) crop injury was recorded. Late season weed control ratings (95–140 days after herbicide application) are presented for all weeds with the exception of Palmer amaranth control at Ganado in 2015 where populations of this weed were low (<4 plants/m<sup>2</sup> ) and somewhat inconsistent. Crop yield was determined by hand‐harvesting 3.8 m of each plot, shelling the kernels from the corn ear, and weighing the kernels. Crop weights were adjusted to 15% moisture.

Visual estimates of weed control and corn injury were transformed to the arcsine square root prior to analysis of variance but are expressed in their original form for clarity because the transformation did not alter interpretation. Means were compared with Fisher's Protected LSD test at the 5% probability level [71]. The non‐treated check was not included in the weed control analysis but was included in corn yield analysis.

#### **2.2. Corn POST studies in central and south Texas**

Field studies were conducted during the 2013 through 2015 growing season at two locations in central Texas including near Taylor (30.5326° N, 97.4548° W) and Beyersville (30.3036° N, 97.1947° W) and at three locations in south‐central Texas near Kendleton (29.44786° N, 95.99961° W), Ganado (29.0438° N, 96.4849° W), and Yoakum (29.1827° N, 97.0929° W). Where study sites were similar over years, these studies were located in different fields within the same general area. Soils at the central Texas locations near Taylor were a Burleson clay (fine, montmoril‐ lonitic, and thermic Udic Pellusterts) with less than 1% organic matter and 7.6 pH, while soils at the Beyersville location soils were a Houston Black clay (fine, smectitic, and thermic Udic Haplusterts) with less than 3% organic matter and 7.8 pH. Soils at the south‐central locations near Ganado were a Laewest clay (fine, montmorillonitic, and thermic Udic Pellusterts) with less than 1% organic matter and 7.4 pH, soils at Kendleton were a Bernard‐Edna complex (fine, smectitic, and hyperthermic Oxyaquic Vertic Argiudolls) with less than 3% organic matter and 6.8 pH. Soils at the Yoakum location were a Cuero sandy clay loam (fine, loamy, mixed, super‐ active, and thermic Pachic Argiustolls) with less than 2% organic matter and 7.2 pH.

Herbicides were applied within 5–7 days after planting with a CO<sup>2</sup>

*reticulatum* (Torr.) Beal] populations in 2013 were moderate (3–4 plants/m<sup>2</sup>

*texana* (Buckley) R. Webster] populations ranged from 6–10 plants/m<sup>2</sup>

populations were higher (6–8 plants/m<sup>2</sup>

years were low to moderate (2–6 plants/m<sup>2</sup>

populations ranged from 2–6 plants/m<sup>2</sup>

adjusted to 15% moisture.

ulations varied from 4–8 plants/m<sup>2</sup>

68 Herbicide Resistance in Weeds and Crops

P. Beauv.] populations in 2015 ranged from 4–8 plants/m<sup>2</sup>

control analysis but was included in corn yield analysis.

**2.2. Corn POST studies in central and south Texas**

sprayer with TeeJet 11002 flat‐fan nozzles (Spraying Systems Co., North Avenue and Schmale Road, Wheaton, IL 60188) using a pressure of 180 kPa and calibrated to deliver 140 or 187 L ha−1 (depending on location). An untreated check was included for comparison at each location. All herbicide doses were based on the USA label dose with the exception of the acetochlor (74.8% formulation) dose which was applied at 2X of the labeled rate throughout the study by mis‐ take. Once the error was realized, it was decided to maintain this dose throughout the study.

Weed populations varied from year to year and were from naturally occurring soil seed bank populations. At the Taylor location, browntop panicum [*Panicum fasciculatum* Sw. var.

location. Hophornbeam copperleaf (*Acalypha ostryifolia* Riddell) populations at Taylor in both

Crop injury and weed control were estimated visually on a scale of 0–100 (0 indicating no control or injury and 100 indicating complete control or plant death). Crop injury consisted of plant stunting and early season (30 days after herbicide application) and late season (95–140 days after application) crop injury was recorded. Late season weed control ratings (95–140 days after herbicide application) are presented for all weeds with the exception of Palmer amaranth control at Ganado in 2015 where populations of this weed were low (<4 plants/m<sup>2</sup>

and somewhat inconsistent. Crop yield was determined by hand‐harvesting 3.8 m of each plot, shelling the kernels from the corn ear, and weighing the kernels. Crop weights were

Visual estimates of weed control and corn injury were transformed to the arcsine square root prior to analysis of variance but are expressed in their original form for clarity because the transformation did not alter interpretation. Means were compared with Fisher's Protected LSD test at the 5% probability level [71]. The non‐treated check was not included in the weed

Field studies were conducted during the 2013 through 2015 growing season at two locations in central Texas including near Taylor (30.5326° N, 97.4548° W) and Beyersville (30.3036° N, 97.1947° W) and at three locations in south‐central Texas near Kendleton (29.44786° N, 95.99961° W), Ganado (29.0438° N, 96.4849° W), and Yoakum (29.1827° N, 97.0929° W). Where study sites were similar over years, these studies were located in different fields within the same general area. Soils at the central Texas locations near Taylor were a Burleson clay (fine, montmoril‐ lonitic, and thermic Udic Pellusterts) with less than 1% organic matter and 7.6 pH, while soils at the Beyersville location soils were a Houston Black clay (fine, smectitic, and thermic Udic

depending on the year.

‐pressurized backpack

), while in 2014

at the Ganado

)

. Palmer amaranth pop‐

). Common barnyardgrass [*Echinochloa crus‐galli* (L.)

), while common sunflower (*Helianthus annuus* L.)

at the Taylor location to 2–10 plants/m<sup>2</sup>

. At Ganado, Texas millet [*Urochloa* 

Studies were arranged in a randomized complete block design with three replicates of treat‐ ments. Plot dimensions were either two or four rows (depending on location), spaced 76–97 cm apart by 6.3–7.9 m long. The corn varieties BH 8846RR (2013), BH 8844 VTTP (2014), and BH 8475 SS (2015) were planted from mid‐February to mid‐March depending on locations and environmental conditions to a depth of approximately 2.5–3.5 cm at the rate of 54,000–65,500 seeds ha−1.

Herbicides were applied POST with a CO<sup>2</sup> ‐pressurized backpack sprayer using TeeJet 11002 flat‐fan nozzles (Spraying Systems Co., North Avenue and Schmale Road, Wheaton, IL 60188) with a pressure of 180 kPa and calibrated to deliver 140–187 L ha−1 (depending on location). An untreated check was included for comparison at each location. All herbicide doses were based on the USA label and included an adjuvant and either ammonium nitrate or sulfate per label requirements.

Weed populations varied from location to location and were from natural seed bank popula‐ tions in the soil. At the Taylor location, browntop panicum populations in 2013 were sparse (3–4 plants/m<sup>2</sup> ), while Texas millet populations at Beasley were extremely dense (16–18 plants/m<sup>2</sup> ) and moderate at Beyersville (6–8 plants/m<sup>2</sup> ). Common barnyardgrass pressure at Taylor was low to moderate (4–8 plants/m<sup>2</sup> ). Palmer amaranth populations at the Yoakum and Ganado locations was dense (16–20 plants/m<sup>2</sup> ), while populations at the Taylor locations were low (4–6 plants/m<sup>2</sup> ). Pitted morningglory (*Ipomoea lacunose* L.), hophornbeam copperleaf, and Asiatic dayflower (*Commelina communis* L.) populations were low to moderate (4–8 plants/m<sup>2</sup> ). Approximately 50% of the Palmer amaranth population at the Ganado location was glyphosate resistant.

Weed size at the time of treatment varied by location. Browntop panicum was no greater than 15 cm tall when treated, while Texas millet and common barnyardgrass were less than 20 cm tall at the time of herbicide application. Palmer amaranth at the Yoakum location was less than 5 cm tall at herbicide application, while at Taylor weed size was less than 20 cm. However, at the Ganado location, Palmer amaranth height varied from 40 to 60 cm due to rains which prevented entry into the field in a timely manner. Pitted morningglory length ranged from 5 to 20 cm, while hophornbeam copperleaf and Asiatic dayflower were less than 20 cm in height at the time of treatment. Corn height varied from location to location but was typically in the V4–V8 stage.

Crop injury and weed control were visually estimated on a scale of 0–100 (0 indicating no control or injury and 100 indicating complete control or plant death). Mid‐ to late season weed control ratings (31–98 days after herbicide application) are presented for all weeds. Crop yield was determined by hand‐harvesting 3.8 m of each plot, shelling the kernels from the corn ear, and weighing the kernels. Crop weights were adjusted to 15% moisture.

Visual estimates of weed control and corn injury were transformed to the arcsine square root prior to analysis of variance but are expressed in their original form for clarity because the transformation did not alter interpretation. Means were compared with Fisher's Protected LSD test at the 5% probability level [71]. The non‐treated check was not included in the weed control analysis but was included in corn yield analysis.

#### **2.3. Cotton studies in south‐central Texas**

Studies were conducted in Burleson County, TX (30.3257° N, 96.2615° W) at the Texas A&M AgriLife Research Farm in 2012 and 2013 to investigate management strategies for controlling Palmer amaranth and common waterhemp in cotton possessing glyphosate‐, glufosinate‐, and dicamba‐tolerant transgenic traits. Studies were in the same general area in each year. Soils at this site are characterized as a Westwood silty clay loam (fine, silty, mixed, superactive, and thermic Udifluventic Haplustepts) with 2% organic matter and 8.1 pH. The experiment included 12 treatments arranged as a randomized complete block design with 4 replications. Plots were four rows wide and 9.1 m in length with 102 cm row spacing. Buffers 4.5 m wide were maintained between blocks to facilitate lateral movement of equipment.

This experiment was conducted on a furrow‐irrigated field with large seed bank populations of both Palmer amaranth and common waterhemp. Both Palmer amaranth and common waterhemp were naturally occurring populations with 10–15 plants/m<sup>2</sup> . In 2012, none of the Palmer amaranth or common waterhemp populations were glyphosate resistant, while in 2013 approximately 10% of the Palmer amaranth population was resistant; however, none of the waterhemp populations were resistant. Treatments included preplant‐incorporated (PPI), PRE, and two POST application timings of an early POST (EPOST) and mid‐POST (MPOST). Plots receiving PPI applications of trifluralin were subjected to two passes of a rolling cultiva‐ tor immediately following application to thoroughly incorporate the herbicide into the soil. Preemergence herbicide applications included fomesafen, pendimethalin, prometryn, pyri‐ thiobac, and *S*‐metolachlor, while POST applications included acetochlor, dicamba, glufos‐ inate, glyphosate, pyrithiobac, and trifloxysulfuron. Early postemergence applications in 2012 were made when weeds were approximately 12 cm tall and in 2013 when weeds were 10 cm in height, while MPOST treatments in 2012 were made when weeds were 25 cm tall and in 2013 when 15 cm in height. An untreated check was included in all studies.

For the 2012 experiment, PPI applications were made on May 7, cotton was planted on May 22, EPOST applications were made on June 21, and MPOST applications were made on July 4. In 2013, PPI applications were made on May 8, cotton was planted on May 9, EPOST applications were made on June 7, and MPOST applications were made on June 16. The cotton variety was an experimental dicamba‐glyphosate tolerant entry from Monsanto. Herbicide applications were made with a CO<sup>2</sup> ‐pressurized backpack sprayer calibrated to deliver 140 L ha−1 total spray volume. Preplant‐incorporated and PRE applications were made using TeeJet 11003 Drift Guard flat‐fan nozzles, while EPOST and MPOST applications were made with TeeJet 110015 Turbo TeeJet Induction flat‐fan nozzles (TeeJet Technologies, Wheaton, Illinois 60187).

Control of Palmer amaranth and common waterhemp was estimated visually at the time of the EPOST application, at the time of MPOST application, and 14 days after the MPOST application. These observations are reported as early, mid, and late, respectively. Plots were managed throughout the season according to standard crop management practices for this region. The center two rows of all plots were mechanically harvested and seed cotton yields were recorded. Means were compared with Fisher's Protected LSD test at the 5% probability level [71].

## **2.4. Cotton studies in the High Plains of Texas**

Visual estimates of weed control and corn injury were transformed to the arcsine square root prior to analysis of variance but are expressed in their original form for clarity because the transformation did not alter interpretation. Means were compared with Fisher's Protected LSD test at the 5% probability level [71]. The non‐treated check was not included in the weed

Studies were conducted in Burleson County, TX (30.3257° N, 96.2615° W) at the Texas A&M AgriLife Research Farm in 2012 and 2013 to investigate management strategies for controlling Palmer amaranth and common waterhemp in cotton possessing glyphosate‐, glufosinate‐, and dicamba‐tolerant transgenic traits. Studies were in the same general area in each year. Soils at this site are characterized as a Westwood silty clay loam (fine, silty, mixed, superactive, and thermic Udifluventic Haplustepts) with 2% organic matter and 8.1 pH. The experiment included 12 treatments arranged as a randomized complete block design with 4 replications. Plots were four rows wide and 9.1 m in length with 102 cm row spacing. Buffers 4.5 m wide

This experiment was conducted on a furrow‐irrigated field with large seed bank populations of both Palmer amaranth and common waterhemp. Both Palmer amaranth and common

Palmer amaranth or common waterhemp populations were glyphosate resistant, while in 2013 approximately 10% of the Palmer amaranth population was resistant; however, none of the waterhemp populations were resistant. Treatments included preplant‐incorporated (PPI), PRE, and two POST application timings of an early POST (EPOST) and mid‐POST (MPOST). Plots receiving PPI applications of trifluralin were subjected to two passes of a rolling cultiva‐ tor immediately following application to thoroughly incorporate the herbicide into the soil. Preemergence herbicide applications included fomesafen, pendimethalin, prometryn, pyri‐ thiobac, and *S*‐metolachlor, while POST applications included acetochlor, dicamba, glufos‐ inate, glyphosate, pyrithiobac, and trifloxysulfuron. Early postemergence applications in 2012 were made when weeds were approximately 12 cm tall and in 2013 when weeds were 10 cm in height, while MPOST treatments in 2012 were made when weeds were 25 cm tall and in 2013

For the 2012 experiment, PPI applications were made on May 7, cotton was planted on May 22, EPOST applications were made on June 21, and MPOST applications were made on July 4. In 2013, PPI applications were made on May 8, cotton was planted on May 9, EPOST applications were made on June 7, and MPOST applications were made on June 16. The cotton variety was an experimental dicamba‐glyphosate tolerant entry from Monsanto. Herbicide applications

spray volume. Preplant‐incorporated and PRE applications were made using TeeJet 11003 Drift Guard flat‐fan nozzles, while EPOST and MPOST applications were made with TeeJet 110015 Turbo TeeJet Induction flat‐fan nozzles (TeeJet Technologies, Wheaton, Illinois 60187). Control of Palmer amaranth and common waterhemp was estimated visually at the time of the EPOST application, at the time of MPOST application, and 14 days after the MPOST application.

‐pressurized backpack sprayer calibrated to deliver 140 L ha−1 total

. In 2012, none of the

were maintained between blocks to facilitate lateral movement of equipment.

waterhemp were naturally occurring populations with 10–15 plants/m<sup>2</sup>

when 15 cm in height. An untreated check was included in all studies.

were made with a CO<sup>2</sup>

control analysis but was included in corn yield analysis.

**2.3. Cotton studies in south‐central Texas**

70 Herbicide Resistance in Weeds and Crops

Field studies were conducted near New Deal (33.4413° N, 101.4358° W) and Halfway, TX (34.1881° N, 101.9522° W) during the 2015 and 2016 growing seasons to investigate manage‐ ment strategies for controlling Palmer amaranth in cotton possessing glyphosate‐, glufosinate‐, dicamba‐, and 2,4‐D choline‐tolerant transgenic traits. Soils at the New Deal site are character‐ ized as a Pullman clay loam (fine, mixed, and superactive thermic Torrertic Paleustolls) with less than 1% organic matter and 7.9 pH, while soils at New Deal are a Olton clay loam (fine, mixed, and thermic Aridic Paleustoll) with less than 1% organic matter and a 7.4 pH. These experiments were conducted under center pivot irrigation at Halfway and 102 cm spacing of sub‐surface drip tape at New Deal with large populations of Palmer amaranth (8–10 plants/m<sup>2</sup> ). These studies were conducted as a randomized complete block design with four replications. Plots were four rows wide and 9.1–12.7 m in length, with 102 cm row spacing.

Treatments for the glyphosate plus 2,4‐D choline study (Enlist Duo) included PPI treatments of trifluralin and EPOST and MPOST treatments of glyphosate, glufosinate, glyphosate plus 2,4‐D choline, *S*‐metolachlor, and 2,4‐D choline salt. Plots receiving PPI applications of tri‐ fluralin were subjected to two passes of a rolling cultivator immediately following applica‐ tion. Postemergence applications were made when Palmer amaranth was 15 cm or less in height. This study was conducted in 2016. The cotton variety was an experimental from Dow AgroSciences (9330 Zionsville Rd, Indianapolis, IN 46268) and was planted on May 26 at a seeding rate of 13.1 seeds m−1 of row.

Treatments for the glyphosate systems study included preplant applications of glyphosate plus either flumioxazin, fomesafen, the premix of rimsulfuron plus thifensulfuron‐methyl, or diruron, PRE applications of either flumeturon, pyrithiobac, acetochlor, or flumeturon plus paraquat, EPOST applications of glyphosate alone or plus either acetochlor, *S*‐meto‐ chlor, dimethenamid‐P, or pyrithiobac, MPOST applications of glyphosate alone or plus acetochlor, dimethenamid‐P, or S‐metochlor, and LPOST treatments of diruron plus MSMA. Postemergence applications were made when Palmer amaranth was 10 cm or less in height. This study was conducted in 2015 and 2016. Fibermax 2322GL was planted in both years with the same seeding rate as in the previous study.

Herbicide applications were made with a CO<sup>2</sup> ‐pressurized backpack sprayer calibrated to deliver 93–140 L ha−1 total spray volume. PPI and PRE applications were made using TeeJet 11002 Drift Guard flat‐fan nozzles, while EPOST and MPOST applications were made with TeeJet 110015 Turbo TeeJet Induction flat‐fan nozzles. A Redball® tractor‐mounted hooded sprayer (Willmar Fabrication, LLC; Willmar, MN 56201) was used for LPOST herbicide applications.

Control of Palmer amaranth was estimated visually as in previous studies. Plots were man‐ aged throughout the season according to standard crop management practices for this region. The center two rows of all plots were mechanically harvested, and lint cotton yields were recorded. Means were compared with Fisher's Protected LSD test at the 5% probability level [71].
