Hostname: page-component-586b7cd67f-t7fkt Total loading time: 0 Render date: 2024-11-22T07:18:25.798Z Has data issue: false hasContentIssue false

Sensitivity of TamArk™ grain sorghum and monocot weed species to ACCase- and ALS-inhibiting herbicides

Published online by Cambridge University Press:  09 August 2023

Jacob Fleming*
Affiliation:
Graduate Research Assistant, Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA
Jason K. Norsworthy
Affiliation:
Distinguished Professor and Elms Farming Chair of Weed Science, Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA
Muthukumar Bagavathiannan
Affiliation:
Professor of Weed Science, Department of Soil and Crop Sciences, Texas A&M University, College Station, TX, USA
Tom Barber
Affiliation:
Professor and Extension Weed Scientist, Cooperative Extension Service, Lonoke, AR, USA
*
Author for correspondence: Jacob Fleming, Graduate Research Assistant, Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, AR 72704, USA Email: [email protected]
Rights & Permissions [Opens in a new window]

Abstract

Only a limited number of herbicides are available to provide postemergence (POST) control of selective monocot weeds in grain sorghum crops. The herbicides currently labeled for use with grain sorghum have strict use restrictions, low efficacy on johnsongrass, or weed resistance issues. To introduce a new effective herbicide mode of action for monocot control, multiple companies and universities have been developing herbicide-resistant grain sorghum that would allow producers to use herbicides that inhibit either acetolactate synthase (ALS) or acetyl coenzyme A carboxylase (ACCase) for POST monocot control. An experiment was conducted in Fayetteville, AR, in 2020 and 2021, to determine the effectiveness of two ALS-inhibiting herbicides and nine ACCase-inhibiting herbicides on TamArk™ grain sorghum, conventional grain sorghum, and problematic monocot weed species. Grain sorghum and monocot weeds (johnsongrass, broadleaf signalgrass, barnyardgrass, and Texas panicum) were sprayed when TamArk grain sorghum reached the 2- to 3-leaf stage. TamArk grain sorghum was tolerant of all ACCase-inhibiting herbicides tested, exhibiting ≤10% injury at all evaluation timings, except clethodim and sethoxydim, and had no resistance to the ALS-inhibiting herbicides that were evaluated. Additionally, all ACCase inhibitors except diclofop and pinoxaden controlled all monocots tested by >91% at 28 d after application (DAA). Conversely, the two ALS inhibitors, imazamox and nicosulfuron, provided ≤81% control of broadleaf signalgrass 28 DAA but still controlled all other monocots by >95%. TamArk grain sorghum has low sensitivity to multiple ACCase-inhibiting herbicides and thus provides an effective POST option for monocot weed control. In addition, unwanted volunteer TamArk plants can be controlled with cledthodim, sethoxydim, nicosulfuron, or imazamox. Although the ALS-inhibiting herbicides imazamox and nicosulfuron were not useful on TamArk grain sorghum, they are effective options for monocot control on Igrowth™ and Inzen™ grain sorghum crops, respectively.

Type
Research Article
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2023. Published by Cambridge University Press on behalf of the Weed Science Society of America

Introduction

The lack of selective postemergence (POST) herbicides that control late-season grass is a concern for many grain sorghum producers in the United States (Smith et al. Reference Smith and Scott2010). Grain sorghum is a member of the Gramineae family, and POST herbicides that control grass weeds have a high risk of severely injuring the crop. Only three herbicides are available for POST grass control in conventional grain sorghum crops: atrazine (categorized as a Group 5 herbicide by the Weed Science Society of America [WSSA]), quinclorac (WSSA Group 4), and paraquat (WSSA Group 22). These herbicides present challenges. Paraquat, for example, requires that applications occur under hoods to mitigate significant crop injury, quinclorac resistance occurs in multiple annual types of grass, and atrazine provides only partial grass control as a POST application (Fromme et al. Reference Fromme, Dotray, Grichar and Fernandez2012; Heap Reference Heap2022).

A significant development in grain sorghum research was the introduction of fluxofenim-based seed treatments that allow producers to use chloroacetamide herbicides such as S-metolachlor and dimethenamid-P preemergence to control both grass and small-seeded broadleaf weeds without injuring grain sorghum (Al-Khatib et al. Reference Al-Khatib, Regehr, Stahlman and Loughin2004). However, relying on chloroacetamide herbicides for grass control presents some concerns when used on grain sorghum crops. Because grain sorghum is commonly grown in hot and dry conditions without irrigation, decreased efficacy of chloroacetamide herbicides can occur (Prasad et al. Reference Prasad, Pisipati, Mutava and Tuinstra2008). Chloroacetamide herbicides require adequate moisture for proper activation, which does not always occur in grain sorghum production (Brown et al. Reference Brown, Chandler and Morrison1988; Regehr et al. Reference Regehr, Peterson, Fick and Stahlman2008). When rainfall is less than 14 mm within the first 2 wk of application, a reduction in chloroacetamide efficacy has been observed on barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] (Jursik et al. Reference Jursik, Kocarek, Hamouzova, Soukup and Venclova2013). Furthermore, chloroacetamide herbicides effectively control seedling johnsongrass [Sorghum halepense (L.) Pers] by more than 95% but they do not control johnsongrass plants that emerge from rhizomes (Scarabel et al. Reference Scarabel, Panozzo, Savoia and Sattin2014). Because a johnsongrass plant can produce 5,000 or more rhizomes in a single growing season, other control options are necessary (McWhorter Reference McWhorter1971).

Options for selective POST grass control in grain sorghum crops are needed. Four companies or universities have focused on developing herbicide-resistant grain sorghum to introduce new herbicides for POST grass control. Two would entail WSSA Group 1 acetyl CoA carboxylase (ACCase) inhibitors, and two would entail WSSA Group 2 acetolactate synthase (ALS) inhibitors.

Corteva (Indianapolis, IN) has developed Inzen™ grain sorghum, which is resistant to the ALS inhibitor nicosulfuron and is currently marketed under the tradename Accent® Q for use in corn (Zea mays L.) crops and labeled for use with grain sorghum as Zest™. Nicosulfuron is a sulfonylurea herbicide used to control problematic grasses in corn, especially johnsongrass (Camacho et al. Reference Camacho, Moshier, Morishita and Devlin1991; Dobbels and Kapusta Reference Dobbels and Kapusta1993). A collaboration between UPL (King of Prussia, PA) and Alta seeds (College Station, TX) led to the commercialization and release in 2021 of grain sorghum that is resistant to the ALS inhibitor imazamox, marketed as Igrowth™. Imazamox, an imidazolinone family herbicide, is commonly known by the tradenames Raptor® or Beyond® (BASF, Triangle Park, NC) and used for grass control in soybean [Glycine max (L.) Merr.] or Clearfield® production systems. While imazamox has been proven to control annual grasses such as barnyardgrass and goosegrass [Eleusine indica (L.) Gaertn] (Fish et al. Reference Fish, Webster, Blouin and Bond2016), little data are available regarding the control of perennial grasses such as johnsongrass.

S&W Seeds (Longmont, CO) collaborated with Adama (Raleigh, NC) to develop grain sorghum that is resistant to the ACCase inhibitor quizalofop, and marketed as Double Team™. Quizalofop is an aryloxyphenoxypropionate (AOPP) herbicide sold under many tradenames but was most recently integrated into rice production through the Provisia® system commercialized by BASF. Quizalofop has successfully controlled problematic annual and perennial grass weeds (Brewster and Spinney Reference Brewster and Spinney1989; Sanders et al. Reference Sanders, Bond, Lawrence, Golden, Allen and Bararpour2020). The University of Arkansas System Division of Agriculture and Texas A&M University collaboratively developed grain sorghum known as TamArk™, which has a mutation in the ACCase gene (Norsworthy et al. Reference Norsworthy, Bagavathiannan and Rooney2020). Preliminary data show this mutation confers resistance to other ACCase inhibitors within the AOPP and phenylpyrazolin (PPN) families (Piveta et al. Reference Piveta, Norsworthy and Bagavathiannan2020).

Adding new herbicide-resistance technologies could significantly improve grass control in grain sorghum. Using effective modes of action not previously labeled for use with grain sorghum could allow producers to control problematic grasses better while helping mitigate resistance (Norsworthy et al. Reference Norsworthy, Ward, Shaw, Llewellyn, Nichols, Webster, Bradley, Frisvold, Powles, Burgos, Witt and Barrett2012). While herbicides that are to be labeled for use on grain sorghum have demonstrated grass control in crops such as rice (Oryza sativa L.), corn, and soybean, it is essential that we understand the control levels of grasses specific to grain sorghum under typical growing conditions. By understanding which herbicides are most effective on certain problematic grasses, producers can better decide which technologies they should use based on specific weed spectra in a specific location. Therefore, we conducted research to determine the effectiveness of two ALS- and nine ACCase-inhibiting herbicides on common grasses of grain sorghum, along with the sensitivity of conventional and TamArk grain sorghum to these herbicides.

Materials and Methods

Field experiments were conducted in 2020 and 2021 at the Milo J. Shult Arkansas Agricultural Research and Extension Center in Fayetteville, AR, on a Leaf silt loam (fine, mixed, active, thermic Typic Albaquults) with 19.6% sand, 57.8% silt, 22.6% clay, and pH 6.2. The experiments were a single-factor randomized complete block design with four replications. Ten ACCase and two ALS inhibitors were evaluated at various rates based on label suggestions for use on crops other than grain sorghum (Table 1). All herbicides were applied with crop oil concentrate at 1% v/v. A nontreated check was included for comparison purposes. The conventional grain sorghum hybrid DK553-67 and TamArk were planted at 18 seeds m−1 row. Initial plans were to include Inzen grain sorghum in this study, but it had to be removed due to research restrictions on the technology. Common grass weeds, including johnsongrass, broadleaf signalgrass [Urochloa platyphylla (Nash) R.D. Webster], barnyardgrass, and Texas panicum [Urochloa texana (Buckl.) R. Webster] included in the study were seeded in individual rows at approximately 40 seeds m−1. All grass weeds were obtained from Azlin Seed Service (Leland, MS). All species, including grain sorghum, were planted into a conventionally tilled area using a Hege drill (Hege Company, Waldenburg, Germany) with individual seed boxes for each row with 38 cm between rows. The plot size was 2 m by 3 m, and herbicides were applied perpendicular to the direction planted. Weeds and crops were not grown past 28 d after application (DAA); hence, only preplant nitrogen was applied based on the Arkansas grain sorghum production handbook (Espinoza Reference Espinoza2015). Broadleaf weeds were removed from all plots using a single application of 2,4-D at 950 g ae ha−1 when grain sorghum was 25 cm tall. No herbicides were sprayed to control natural grass populations to ensure the planted grasses were not injured or controlled before treatment applications. Treatments were applied when grain sorghum reached the 2- to 3-leaf stage (Table 2) using a CO2-pressurized backpack sprayer, and a 6-nozzle boom with air induction extended range (AIXR) 110015 nozzles (TeeJet, Springfield, IL) spaced 50 cm apart at 4.8 kph delivering 140 L ha−1. Boom height was 46 cm above the tallest plant in the plot to achieve proper coverage.

Table 1. Herbicides and rates applied for monocot tolerance studies in 2020 and 2021. a

a Abbreviations: ACCase, acetyl coenzyme A carboxylase; ALS, acetolactate synthase; WSSA, Weed Science Society of America.

Table 2. Average density and leaf stage of grain sorghum and grasses at the time of herbicide application. a

a Field experiments were conducted in Fayetteville, Arkansas, in 2020 and 2021.

b Density recorded as plants per meter of row.

c Size recorded as number of true leaves present.

Both ACCase and ALS inhibitors typically elicit minimal symptoms in plants the first 7 d after treatment. Therefore, grain sorghum was evaluated for visible injury 14, 21, and 28 DAA. The injury was rated on a 0% to 100% scale, where 0% equals no visible injury, and 100% equals total crop mortality (Frans and Talbert Reference Frans and Talbert1986). Similarly, visible grass control was rated the same days on a scale of 0% to 100%, where 0% equals no control, and 100% equals no living tissue present (Frans and Talbert Reference Frans and Talbert1986). At 28 DAA, aboveground living tissue was collected by species or grain sorghum type. All living plants within 1 m of the row of each species in each plot were collected and air dried at 60 C for 2 wk, then removed and weighed individually. Data were used to calculate percent biomass reduction by species using the following equation:

(1) ${{Nontreated\,\left( g \right) - treated\,\left( g \right)} \over {nontreated\,\left( g \right)}}\; \times \;100$

Data Analysis

All nontreated plots were rated 0% at all evaluation timings across all species; hence, they were excluded from the statistical analysis. The distribution function in JMP 16.1 Pro software (SAS Institute Inc., Cary, NC) was used to determine the correct distribution to analyze each variable based on corrected Akaike Information Criterion (AICc) and Bayesian Information Criterion (BIC) values. Visible control ratings of all grass species and conventional grain sorghum injury 14, 21, and 28 DAA were determined to follow a beta distribution. The visible sensitivity of TamArk grain sorghum to the herbicides followed a gamma distribution. Biomass reduction for each grass species and grain sorghum type followed a beta distribution. A single-factor statement was developed with the main effect of herbicide treatment for grain sorghum and all grass weeds at each evaluation timing and biomass reduction using the GLIMMIX procedure with SAS software (version 9.4; SAS Institute Inc., Cary, NC). Block and year were considered random effects in all statements. When herbicide treatment was significant, visible control and biomass reduction were subjected to mean separation using Tukey’s HSD at α = 0.05.

Results and Discussion

Conventional Grain Sorghum Sensitivity

High injury and biomass reduction levels occurred, ranging from 94% to 100% across all evaluation timings and herbicides other than pinoxaden and diclofop (Table 3). Pinoxaden and diclofop caused less injury than all other herbicide treatments at each respective evaluation timing. However, the injury was ≥67% by 28 DAA for both herbicides, which producers would deem to be unacceptable. Like the injury evaluations, all treatments resulted in >99% biomass reduction, other than pinoxaden and diclofop, which caused 81% and 83% reduction in biomass, respectively. None of the evaluated herbicides are labeled for conventional grain sorghum, and it is known that grain sorghum is susceptible to ACCase inhibitors (Lancaster et al. Reference Lancaster, Norsworthy and Scott2018); hence, high injury levels were expected.

Table 3. Percent visible injury and biomass reduction of DK553-67 grain sorghum by herbicide and rate, averaged over the years. a,b,c

a Abbreviation: DAA, days after application.

b Field experiments were conducted in Fayetteville, Arkansas, in 2020 and 2021.

c Means within a column followed by the same letter are not significantly different based on Tukey’s HSD (α = 0.05).

d Percent reduction is relative to the nontreated plot within each replication.

TamArk Grain Sorghum Sensitivity

Differences in injury and biomass reduction of TamArk grain sorghum occurred among the herbicides tested at all evaluation timings (Table 4). Two ALS inhibitors, nicosulfuron and imazamox, completely controlled TamArk grain sorghum by 28 DAA, and biomass was reduced 100%. Since no known mutations to the ALS gene are present in TamArk grain sorghum, the high sensitivity to these herbicides was expected.

Table 4. Percent visible injury and biomass reduction of TamArk™ grain sorghum by various herbicides and rates, averaged over the years. a,b,c

a Abbreviation: DAA, days after application.

b Field experiments were conducted in Fayetteville, Arkansas, in 2020 and 2021.

c Means within a column followed by the same letter are not significantly different based on Tukey’s HSD (α = 0.05).

d Percent reduction is relative to the nontreated plot within each replication.

Among the ACCase inhibitors, the greatest injury resulted from the cyclohexanedione family, for which complete control was achieved with clethodim and sethoxydim by 21 DAA (Table 4). Conversely, the ACCase inhibitors from the AOPP and PPN families, specifically clodinafop, cyhalofop, diclofop, fenoxaprop, fluazifop, quizalofop, and pinoxaden, produced relatively low injury levels, with the highest being 10% caused by quizalofop at 92 g ha−1 at 28 DAA. Similarly, Piveta et al. (Reference Piveta, Norsworthy and Bagavathiannan2020) observed high resistance to fluazifop, fenoxaprop, and quizalofop when conducting dose-response experiments on TamArk grain sorghum. Therefore, when labeled, herbicides from the AOPP and PPN families could be safely used for grass control in TamArk grain sorghum.

Johnsongrass Control

Like conventional grain sorghum, johnsongrass control by treatment varied 14 DAA, ranging from 80% to 100% across herbicide treatments, excluding the pinoxaden and diclofop treatments (Table 5). Diclofop at 1,120 g ha−1 and pinoxaden at 60 g ha−1 provided only 32% and 59% johnsongrass control 14 DAA. Johnsongrass control increased over time with pinoxaden, resulting in 92% control by 28 DAA; however, diclofop control 28 DAA was only 38%, a level that was unacceptable. Like the levels of johnsongrass control 28 DAA, all ACCase-inhibiting herbicide treatments, except diclofop and pinoxaden, produced ≥93% johnsongrass biomass reduction. While multiple herbicide treatments resulted in high levels of control, any treatment that did not provide 100% control may not be adequate since there is potential for seed or rhizome production from these surviving plants. Those herbicides that provided complete johnsongrass control and biomass reduction by 28 DAA included clethodim, sethoxydim, fenoxaprop, fluazifop, and quizalofop. Of these, only fluazifop, fenoxaprop, and quizalofop would be viable options for johnsongrass control in TamArk grain sorghum based on the low levels of injury caused by these herbicides (Table 4). Before 2022, no POST herbicide was available for johnsongrass control in grain sorghum; therefore, adding multiple ACCase-inhibiting herbicides such as those evaluated here would provide much-needed johnsongrass control options in grain sorghum production (Smith et al. Reference Smith and Scott2010).

Table 5. Percent visible control and biomass reduction of johnsongrass by various herbicides and rates, averaged over the years. a,b,c

a Abbreviation: DAA, days after application.

b Field experiments were conducted in Fayetteville, Arkansas, in 2020 and 2021.

c Means within a column followed by the same letter are not significantly different based on Tukey’s HSD (α = 0.05).

d Percent reduction is relative to the nontreated plot within each replication.

Broadleaf Signalgrass Control

Control of broadleaf signalgrass varied among herbicide treatments 14 DAA, with the greatest control (≥90%) achieved with clethodim, sethoxydim, the two highest rates of fluazifop, both rates of fenoxaprop, pinoxaden, and all three rates of quizalofop; albeit none provided complete control (Table 6). By 21 DAA, clethodim, fenoxaprop (120 g ha−1), and quizalofop (92 g ha−1) provided 100% control of broadleaf signalgrass. At 28 DAA, a more apparent separation in treatments could be observed, specifically between the ALS and ACCase inhibitors. Both rates of imazamox and nicosulfuron at 28 DAA provided lower levels of broadleaf signalgrass control than all but one ACCase inhibitor treatment (diclofop). Like control levels, imazamox and nicosulfuron generally caused less broadleaf signalgrass biomass reduction than the ACCase-inhibiting herbicides, other than diclofop. Diclofop controlled broadleaf signalgrass by only 27% and reduced its biomass by 45%, which was not surprising considering it is listed as “suppressed” by the herbicide at the 3-leaf growth stage or smaller, according to the label (Anonymous 2003). Broadleaf signalgrass in this trial produced only 4 to 6 leaves in both years, which explains the low levels of control we observed (Table 2). Similarly, imazamox is reported to achieve suppression of only 2- to 5-leaf broadleaf signalgrass unless sequential applications are made (Anonymous 2019), and nicosulfuron is labeled for control of broadleaf signalgrass only when plants are no larger than 5 cm in height (Anonymous 2021). Because of the low levels of control achieved with the two ALS inhibitors or diclofop, these herbicides would not be recommended for broadleaf signalgrass control. Since TamArk grain sorghum is also sensitive to clethodim, fenoxaprop, quizalofop, or fluazifop would be recommended for broadleaf signalgrass control.

Table 6. Percent visible control and biomass reduction of broadleaf signalgrass by various herbicides and rates, averaged over the years. a,b,c

a Abbreviation: DAA, days after application.

b Field experiments were conducted in Fayetteville, Arkansas, in 2020 and 2021.

c Means within a column followed by the same letter are not significantly different based on Tukey’s HSD (α = 0.05).

d Percent reduction is relative to the nontreated plot within each replication.

Barnyardgrass Control

All treatments resulted in 100% control of barnyardgrass across all application timings, except diclofop, which provided 91% control (Table 7). Similarly, all treatments except diclofop reduced biomass by 100%. Overall, the ACCase and ALS inhibitors controlled barnyardgrass, exceeding the effectiveness of traditional herbicides used for POST barnyardgrass control in grain sorghum (Grichar et al. Reference Grichar, Beslar and Brewer2005). Based on the diclofop label (Anonymous 2003), the herbicide is not recommended to control larger than 4-leaf barnyardgrass, which was present in plots (Table 2).

Table 7. Percent visible control and biomass reduction of barnyardgrass by various herbicides and rates, averaged over the years. a,b,c

a Abbreviation: DAA, days after application.

b Field experiments were conducted in Fayetteville, Arkansas, in 2020 and 2021.

c Means within a column followed by the same letter are not significantly different based on Tukey’s HSD (α = 0.05).

d Percent reduction is relative to the nontreated plot within each replication.

Texas Panicum Control

Complete control of Texas panicum was obtained at 14 DAA with all evaluated treatments, except diclofop (Table 8). By 28 DAA, Texas panicum control with diclofop improved, with all herbicide treatments providing complete control. The high levels of control were reflected in the complete absence of this species by 28 DAA for all herbicide treatments. Texas panicum is a common problematic weed of grain sorghum (Van Wychen Reference Van Wychen2020), and high levels of control are seldom achieved in the crop (Grichar et al. Reference Grichar, Beslar and Brewer2004). One of the most effective means of controlling Texas panicum in grain sorghum has been dimethenamid-p and atrazine, which generally provide <80% control (Grichar et al. Reference Grichar, Beslar and Brewer2004). Another herbicide evaluated for Texas panicum control in grain sorghum is quinclorac. Still, control is <40% (Kering et al. Reference Kering, Huo, Interrante, Hancock and Butler2013), a level much lower than that achieved here with both ALS and ACCase inhibitors.

Table 8. Percent visible control and biomass reduction of Texas panicum by various herbicides and rates, averaged over the years. a,b,c

a Abbreviation: DAA, days after application.

b Field experiments were conducted in Fayetteville, Arkansas, in 2020 and 2021.

c Means within a column followed by the same letter are not significantly different based on Tukey’s HSD (α = 0.05).

d Percent reduction is relative to the nontreated plot within each replication.

Practical Implications

With commercial tolerance to the AOPP and PPN herbicides within the ACCase-inhibitor group, TamArk grain sorghum can control the problematic grass weeds within grain sorghum using various POST herbicides based on label recommendations. Both fenoxaprop (120 g ai ha−1) and quizalofop (96 g ai ha−1) provided complete control of all grass weeds tested, making them ideal options for grass control in TamArk grain sorghum. Neither of these herbicides at the rates tested caused more than 10% injury or biomass reduction to TamArk grain sorghum.

While TamArk grain sorghum did not tolerate the ALS inhibitors we evaluated, these herbicides could be used in the labeled technology platform Inzen or Igrowth, for grass control. However, these herbicides were less effective than fenoxaprop or quizalofop at controlling broadleaf signalgrass. Imazamox and nicosulfuron could be used to remove volunteer TamArk grain sorghum from fields planted with Inzen or Igrowth traits. The availability of ACCase and ALS inhibitors to grain sorghum offers producers sites of action that are also effective for johnsongrass control POST, an option that has not been previously available (Smith et al. Reference Smith and Scott2010). One consideration with this research is climate and its effects on the efficacy of these herbicides. Grain sorghum is grown in many areas across the United States, which range from humid subtropical to arid climates. Although this research was conducted in a humid climate, when grain sorghum is planted in arid climates such as the Central Plains, a reduction in efficacy may occur.

ACCase and ALS inhibitors further offer a way to help mitigate herbicide resistance by adding two effective sites of action for grass control in grain sorghum (Norsworthy et al. Reference Norsworthy, Ward, Shaw, Llewellyn, Nichols, Webster, Bradley, Frisvold, Powles, Burgos, Witt and Barrett2012). By using either ACCase or ALS inhibitors in grass control efforts in grain sorghum crops, producers can reduce the pressure on quinclorac, which has been extensively used for grass control in both rice and grain sorghum crops in specific locations, leading to more quinclorac-resistant grass weed populations (Talbert and Burgos Reference Talbert and Burgos2007; Heap Reference Heap2022). It is also important to note that ALS- or ACCase-inhibitor–resistant populations of all the grasses evaluated in this study have been documented in the United States and other countries (Heap Reference Heap2022). While these resistant grass populations are not widespread, it will be important not to overuse ACCase or ALS inhibitors for grass control in grain sorghum so as to mitigate future resistance. Therefore, these technologies should be used in a program approach that combines proper chemical, cultural, and mechanical weed control methods to reduce herbicide resistance risk.

Acknowledgments

We thank the University of Arkansas Department of Crop, Soil, and Environmental Sciences for providing the opportunity to conduct this research. We also thank the graduate assistants and the program technicians for their help with this research. This research received no specific grant from any funding agency, commercial or not-for-profit sectors. No conflicts of interest have been declared.

Footnotes

Associate Editor: Lawrence E. Steckel, University of Tennessee

References

Al-Khatib, K, Regehr, DL, Stahlman, PW, Loughin, TM (2004) Safening grain sorghum injury from metsulfuron with growth regulator herbicides. Weed Sci 52:319325 Google Scholar
Anonymous (2003) Hoelon® 3EC herbicide label. Research Triangle Park, NC: Bayer Crop Science 13 pGoogle Scholar
Anonymous (2021) Zest™ WDG herbicide label Corteva publication No. CD02-635-020. Wilmington, DE: Corteva. 17 pGoogle Scholar
Anonymous (2019) Beyond® herbicide label. BASF publication NVA 2019-04-191-0038. Research Triangle Park, NC: BASF 22 pGoogle Scholar
Brewster, BD, Spinney, RL (1989) Control of seedling grasses with postemergence grass herbicides. Weed Technol 3:3943 CrossRefGoogle Scholar
Brown, S, Chandler, J, Morrison, J (1988) Glyphosate for johnsongrass (Sorghum halepense) control in no-till sorghum (Sorghum bicolor). Weed Sci 36:510513 CrossRefGoogle Scholar
Camacho, RF, Moshier, LJ, Morishita, DW, Devlin, DL (1991) Rhizome johnsongrass (Sorghum halepense) control in corn (Zea mays) with primisulfuron and nicosulfuron. Weed Technol 5:789794 CrossRefGoogle Scholar
Dobbels, AF, Kapusta, G (1993) Postemergence weed control in corn (Zea mays) with nicosulfuron combinations. Weed Technol 7:844850 CrossRefGoogle Scholar
Espinoza, L (2015) Fertilization and Liming. Arkansas Grain Sorghum Production Handbook. MP297:21-24. Little Rock: University of Arkansas Cooperative Extension ServiceGoogle Scholar
Fish, JC, Webster, EP, Blouin, DC, Bond, JA (2016) Imazamox plus propanil mixtures for grass weed management in imidazolinone-resistant rice. Weed Technol 30:2935 CrossRefGoogle Scholar
Frans, R, Talbert, R (1986) Pages 2946 in Experimental design and techniques for measuring and analyzing plant responses to weed control practices. 3rd ed. Champaign, IL: Weed Science Society of America Google Scholar
Fromme, DD, Dotray, PA, Grichar, WJ, Fernandez, CJ (2012) Weed control and grain sorghum tolerance to pyrasulfotole plus bromoxynil. Int J Agron 2012:110 Google Scholar
Grichar, WJ, Beslar, BA, Brewer, KD (2004) Effect of row spacing and herbicide dose on weed control and grain sorghum yield. Crop Prot 23:263267 CrossRefGoogle Scholar
Grichar, WJ, Beslar, BA, Brewer, KD (2005) Weed control and grain sorghum (Sorghum bicolor) response to postemergence applications of atrazine, pendimethalin, and trifluralin. Weed Technol 19:9991003 CrossRefGoogle Scholar
Heap, I (2022) The International Herbicide-resistant Weed Database. www.weedscience.org. Accessed: February 7, 2022Google Scholar
Jursik, M, Kocarek, M, Hamouzova, K, Soukup, J, Venclova, V (2013) Effect of precipitation on the dissipation, efficacy, and selectivity of three chloroacetamide herbicides in sunflower. Plant Soil Environ 59:175182 CrossRefGoogle Scholar
Kering, MK, Huo, C, Interrante, SM, Hancock, DW, Butler, TJ (2013) Effect of various herbicides on warm-season grass weeds and switchgrass establishment. Crop Sci 53:666673 CrossRefGoogle Scholar
Lancaster, ZD, Norsworthy, JK, Scott, RC (2018) Sensitivity of grass crops to low rates of quizalofop. Weed Technol 32:304308 CrossRefGoogle Scholar
McWhorter, CG (1971) Anatomy of johnsongrass. Weed Sci 19:385393 CrossRefGoogle Scholar
Norsworthy, JK, Bagavathiannan, M, Rooney, W (2020) November 30. Herbicide-resistant grain sorghum. U.S. patent application 17/106,881, filed November 30, 2020Google Scholar
Norsworthy, JK, Ward, SM, Shaw, DR, Llewellyn, RS, Nichols, RL, Webster, TM, Bradley, KW, Frisvold, G, Powles, SB, Burgos, NR, Witt, WW, Barrett, M (2012) Reducing the risks of herbicide resistance: best management practices and recommendations. Weed Sci 60(SP1):3162 CrossRefGoogle Scholar
Piveta, LB, Norsworthy, JK, Bagavathiannan, MV (2020) Evaluation of ACCase-resistant grain sorghum to fluazifop at different growth stages. Page 39 in Proceedings of the Southern Weed Science Society 73rd Annual Meeting, Biloxi, Mississippi, January 27–30, 2020Google Scholar
Prasad, PV, Pisipati, SR, Mutava, RN, Tuinstra, MR (2008) Sensitivity of grain sorghum to high temperature stress during reproductive development. Crop Sci 48:19111917 CrossRefGoogle Scholar
Regehr, DL, Peterson, DE, Fick, WH, Stahlman, PW (2008) Chemical weed control for field crops, pastures, rangeland, and noncropland. Manhattan: Kansas State University Agricultural Experiment Station and Cooperative Extension Service Google Scholar
Sanders, TL, Bond, JA, Lawrence, BH, Golden, BR, Allen, TW, Bararpour, T (2020) Evaluation of weed control in acetyl coA carboxylase-resistant rice with mixtures of quizalofop and auxinic herbicides. Weed Technol 34:498505 CrossRefGoogle Scholar
Scarabel, L, Panozzo, S, Savoia, W, Sattin, M (2014) Target-Site ACCase-resistant johnsongrass (Sorghum halepense) selected in summer dicot crops. Weed Technol 28:307315 CrossRefGoogle Scholar
Smith, K, Scott, B (2010) Weed control in grain sorghum. Pages 4749 in Grain Sorghum Production Handbook. Little Rock: University of Arkansas Department of Agriculture Cooperative Extension Service Google Scholar
Talbert, RE, Burgos, NR (2007) History and management of herbicide-resistant barnyardgrass (Echinochloa crus-galli) in Arkansas rice. Weed Technol 21:324331 CrossRefGoogle Scholar
Van Wychen, L (2020) 2020 Survey of the most common and troublesome weeds in grass crops, pasture, and turf in the United States and Canada. Weed Science Society of America National Weed Survey Dataset. https://wssa.net/wp-content/uploads/2020-Weed-Survey_grass-crops.xlsx. Accessed: November 12, 2020Google Scholar
Figure 0

Table 1. Herbicides and rates applied for monocot tolerance studies in 2020 and 2021.a

Figure 1

Table 2. Average density and leaf stage of grain sorghum and grasses at the time of herbicide application.a

Figure 2

Table 3. Percent visible injury and biomass reduction of DK553-67 grain sorghum by herbicide and rate, averaged over the years.a,b,c

Figure 3

Table 4. Percent visible injury and biomass reduction of TamArk™ grain sorghum by various herbicides and rates, averaged over the years.a,b,c

Figure 4

Table 5. Percent visible control and biomass reduction of johnsongrass by various herbicides and rates, averaged over the years.a,b,c

Figure 5

Table 6. Percent visible control and biomass reduction of broadleaf signalgrass by various herbicides and rates, averaged over the years.a,b,c

Figure 6

Table 7. Percent visible control and biomass reduction of barnyardgrass by various herbicides and rates, averaged over the years.a,b,c

Figure 7

Table 8. Percent visible control and biomass reduction of Texas panicum by various herbicides and rates, averaged over the years.a,b,c