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Spot spraying applications offer the opportunity to target specific weeds in a field, while simultaneously reducing herbicide usage and increasing the long‐term efficacy of chemical control options. The study is focused on controlling California weedy rice accessions (Oryza spp.) and problematic grass weeds with a spot spray application of clethodim in a flooded rice system. The efficacy of incorporating nonionic surfactant to clethodim applications was also assessed. Dose‐response experiments were carried out in a greenhouse on five weedy rice accessions, common grass rice weeds, and cultivated rice varieties L207, M105, M206, M209, M211, and S102 to determine the dose needed to affect these populations. Clethodim was applied in a field setting to assess spot spraying efficacy, the possibility of herbicide dispersion in the water, and crop injury. Clethodim successfully controlled weedy rice and grasses in the greenhouse. The effective rates to control 90% of the five test populations (ED90) were between 51 and 74 g ai ha−1 clethodim for weedy rice accessions. Adding nonionic surfactant to clethodim increased its efficacy by 1.6‐ to 1.9‐fold. Cultivated rice varieties did not exhibit any tolerance to clethodim, however, spot spraying applications at 150 g ai ha−1 clethodim did not cause any dispersion in the field. Clethodim spot spray application was effective both at the three‐ to four‐leaf growth stage and tillering growth stage for weedy rice. Core Ideas Spot spray herbicide application successfully controlled weedy rice. Adding nonionic surfactant (NIS) increased the efficacy of clethodim. Clethodim at labeled rate did not cause rice injury outside the spot spray area in rice field. Clethodim spot spray was effective both at the three to four‐leaf growth stage and tillering growth stage for weedy rice.

Control of glyphosate-resistant (GR) junglerice is a challenging task in eastern Australia. There is limited information on the efficacy and reliability of alternate herbicides for GR populations of junglerice, especially when targeting large plants and when temperatures are high. A series of experiments were conducted to confirm the level of glyphosate resistance in three populations of junglerice and to evaluate the efficacy of alternate herbicides for the control of GR junglerice populations. The LD50 of glyphosate of B17/7, B17/34, and B17/35 populations was found to be 298, 2,260, and 1,715 g ae ha–1, respectively, suggesting that populations B17/34 and B17/35 were highly resistant to glyphosate. Glyphosate efficacy was reduced at high-temperature (35 C day/25 C night) compared with low-temperature conditions (25 C day/15 C night), suggesting that control of susceptible populations may also be reduced if glyphosate is sprayed under hot conditions. Preemergence herbicides dimethenamid-P (1,000 g ai ha–1) and pendimethalin (1,500 g ai ha–1) provided 100% control of GR populations (B17/34 and 17/35). Postemergence herbicides, such as clethodim (60 or 90 g ai ha–1), glufosinate (750 g ai ha–1), haloxyfop (52 or 78 g ai ha–1), and paraquat (400 or 600 g ai ha–1), applied at the four-leaf stage provided 100% control of GR populations. For larger junglerice plants (eight-leaf stage), postemergence applications of paraquat (400 or 600 g ai ha–1) provided greater weed control than clethodim, glufosinate, and haloxyfop. A mixture of either glufosinate or haloxyfop with glyphosate provided poor control of GR junglerice populations compared with application of glufosinate or haloxyfop applied alone. Efficacy of glufosinate and haloxyfop for the control of GR populations decreased when applied in the sequential spray after glyphosate application. This study identified alternative herbicide options for GR junglerice populations that can be used in herbicide rotation programs for sustainable weed management. Nomenclature: Clethodim; dimethenamid-P; glufosinate; glyphosate; haloxyfop; paraquat; pendimethalin; junglerice; Echinochloa colona (L.) Link

Junglerice has become a major weed in the mid-south and other areas of the United States. Glyphosate resistance has been documented in junglerice populations and is part of the reason for the increase in its prevalence. However, reduced junglerice control with glyphosate + dicamba and clethodim + dicamba mixtures has been observed in many production fields where glyphosate resistance has not yet evolved. Therefore, research was conducted to assess reduced junglerice control with glyphosate and clethodim when applied with dicamba. Adding dicamba to the spray tank with glyphosate reduced junglerice control by 27%. Adding dicamba to the spray tank with clethodim reduced junglerice control by 11%. The use of Turbo Teejet Induction (TTI) nozzles reduced junglerice control an additional 8% compared to applications with an air induction extended range (AIXR) nozzle. When a drift reduction agent (DRA) was added to dicamba mixtures with glyphosate or clethodim, junglerice control was reduced 36%. Junglerice control was similar with the glyphosate + dicamba treatment compared to the glyphosate + 2,4-D mixture. There was no interaction between nozzles and herbicide treatment. Regardless of herbicide treatment junglerice control was always lower when applied with the ultracourse TTI nozzle. Many applicators in Tennessee prefer to make one application of glyphosate + dicamba in a mixture to save time (authors' personal experience). These results show that the addition of dicamba to glyphosate or clethodim applied with labeled nozzles and a DRA results in reduced junglerice control and should be avoided. Nomenclature: junglerice; Echinochloa colona (L.) Link

We describe a sensitive photoelectrochemical (PEC) sensor for the determination of the herbicide clethodim. The PEC sensor was constructed by using amino-MIL-125/TiO 2 (MIL stands for Materials from Institute Lavoisier), an amino-functionalized metal-organic framework (MOF) modified with TiO 2 . The amino-MIL-125/TiO 2 was synthesized by a simple one-step solvothermal method and placed on a glassy carbon electrode where it displays photoelectrocatalytic activity. Scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and X-ray diffractometry (XRD) were used to characterize the amino-MIL-125/TiO 2 . In the sensing process, amino-MIL-125/TiO 2 is illuminated by visible light to produce electrons. These excited electrons are delivered to the glassy carbon electrode, leaving positively charged holes (h + ) on the surface of the amino-MIL-125/TiO 2 . The holes react with H 2 O to generate hydroxy radicals (•OH). Clethodim rapidly attacks the hydroxy radicals and improves the efficiency of charge separation, this leading to an enhanced photocurrent. Under the optimal experimental conditions, this photoelectrochemical method enables clethodim to be quantified in the concentration range from 0.2 to 25 μmol L −1 , with a detection limit (3 S/N) of 10 nmol L −1 . The assay was applied to the determination of clethodim in soil samples, and results were in acceptable agreement with data obtained by liquid chromatography/mass spectrometry. Graphical Abstract An amino-functionalized metal-organic framework (MOF) modified with titanium dioxide was synthesized and used as a new platform for photoelectrochemical sensing of the herbicide clethodim.

Proper management of glufosinate in glufosinate-resistant crop technologies is needed to mitigate the likelihood of resistance evolution. Antagonism may result from mixtures of glufosinate and other commonly used POST herbicides in soybean and cotton. Two experiments were conducted at the Arkansas Agricultural Research and Extension Center in Fayetteville, AR, in 2015 and 2016 to evaluate mixtures of glufosinate + clethodim and glufosinate + glyphosate on barnyardgrass, broadleaf signalgrass, johnsongrass, and large crabgrass. Furthermore, droplet spectra analyses were conducted to determine if droplet size was associated with identification of herbicide interactions. Antagonism was dependent on the herbicide rates and the weed species. For barnyardgrass and large crabgrass control 4 wk after treatment, glufosinate + glyphosate was antagonistic at all rates evaluated. When large crabgrass was evaluated, some mixtures (e.g., 595 g ha–1 glufosinate + 76 g ha–1 clethodim) had a significant reduction in control relative to one of the herbicides applied alone. Glufosinate (451 and 595 g ai ha–1) + glyphosate (867 and 1,735 g ae ha–1) was antagonistic at all four possible rate combinations for broadleaf signalgrass control. Fewer instances of antagonism were observed for seedling johnsongrass control than for other species, but certain treatments were identified as antagonistic (e.g., glufosinate at 451 g ai ha–1 + clethodim at 76 g ai ha–1). Overall, antagonism was less likely and greater control was observed when the highest rates of both herbicides in a given mixture were used. The addition of glyphosate or clethodim to glufosinate can increase the volume median diameter and decrease the percentage volume of fines, compared to glufosinate alone. The droplet spectra analyses indicate that the glufosinate performance may be negatively affected by the addition of glyphosate or clethodim. Nomenclature: Clethodim; glyphosate; glufosinate; barnyardgrass, Echinochloa crus-galli (L.) Beauv.; broadleaf signalgrass, Urochloa platyphylla (Griseb.) Nash; johnsongrass, Sorghum halepense (L.) Pers.; large crabgrass, Digitaria sanguinalis L.; cotton, Gossypium hirsutum L.; soybean, Glycine max (L.) Merr.

Junglerice has become a major weed in Tennessee cotton and soybean fields. Glyphosate has been relied on to control these accessions over the past two decades, but in recent years cotton and soybean producers have reported junglerice escapes after glyphosate + dicamba and/or clethodim applications. In the growing seasons of 2018 and 2019, a survey was conducted of weed escapes in dicamba-resistant (DR) crops. Junglerice was the most prevalent weed escape in these DR (Roundup Ready Xtend®) cotton and soybean fields in both years of the study. In 2018 and 2019, junglerice was found 76% and 64% of the time in DR cotton and soybean fields, respectively. Progeny from junglerice seeds collected during this survey was screened for glyphosate and clethodim resistance. Seventy percent of the junglerice accessions tested had an effective relative resistance factor to glyphosate of 3.1 to 8.5. In all, 13% of the junglerice accessions could no longer be effectively controlled with glyphosate. This research also showed that all sampled accessions could still be controlled with clethodim in a greenhouse environment, but less control was observed in the field. These data also suggest that another cause for the poor junglerice control is dicamba antagonism of glyphosate and clethodim activity. Nomenclature: Clethodim; dicamba; glyphosate; junglerice [Echinochloa colona (L.) Link]; cotton (Gossypium hirsutum L.); soybean [Glycine max (L.) Merr.]

Owing to the lack of effective POST herbicide options, producers typically rely on nicosulfuron as the main POST grass herbicide in sweet corn production systems. In 2019, a Wisconsin sweet corn producer reported fall panicum control escapes after spraying nicosulfuron. Seeds from mature plants were collected to (1) measure fall panicum response to acetolactate synthase (ALS)-inhibiting herbicides, (2) elucidate the resistance mechanism, and (3) evaluate its response to alternative POST herbicides. Greenhouse and laboratory investigations were conducted to assess fall panicum response to ALS-inhibiting herbicides and elucidate the resistance mechanism. Dose–response results showed that fall panicum was highly resistant to nicosulfuron with a resistance ratio of >12.9-fold (survived rates >254 g ai ha–1, or 8× the field label rate). Molecular and genetic studies indicated that there are multiple ALS gene copies in fall panicum and that resistance was due to a mutation in one copy, resulting in an Asp-376Glu amino acid substitution. Additional greenhouse experiments indicate that clethodim (105 g ai ha–1), quizalofop-p-ethyl (70 g ae ha–1), glyphosate (864 g ae ha–1), and glufosinate (650 g ai ha–1) are effective POST options to manage the ALS-resistant fall panicum (>90.0% control and 96.8% biomass reduction) in rotational years. The 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides isoxaflutole (105 g ai ha–1), mesotrione (105 g ai ha–1), tembotrione (92 g ai ha–1), and tolpyralate (39 g ai ha–1) did not provide effective POST fall panicum control. Because these herbicides are commonly used for POST weed control in sweet corn, more investigations are required to evaluate combinations of HPPD-inhibiting herbicides with herbicides from other sites of action for POST fall panicum control. Herein we confirm the first case of herbicide resistance in fall panicum in the United States. Nomenclature: clethodim; glufosinate; glyphosate; isoxaflutole; mesotrione; nicosulfuron; tembotrione; tolpyralate; quizalofop-p-ethyl; fall panicum; Panicum dichotomiflorum Michx.; sweet corn; Zea mays L. var. saccharate

Despite widespread adoption of dicamba/glyphosate‐resistant (DGR) soybean [Glycine max (L.) Merr.] in Nebraska and across the United States in recent years, economic information comparing herbicide programs with glufosinate‐resistant (GLU‐R) and conventional soybean is not available. The objectives of this study were to evaluate weed control efficacy, crop safety, gross profit margin, and benefit/cost ratios of herbicide programs with multiple sites of action in DGR, GLU‐R, and conventional soybean. Field experiments were conducted in 2018 and 2019 at three irrigated and two rain‐fed locations across Nebraska, for a total of 10 site‐years. Herbicides applied pre‐emergence (PRE) that included herbicides with three sites of action provided 85–99% control of common lambsquarters (Chenopodium album L.), Palmer amaranth (Amaranthus palmeri S. Watson), velvetleaf (Abutilon theophrasti Medik.), and a mixture of foxtail (Seteria spp.) and Poaceae species. Pre‐emergence herbicides evaluated in this study provided 72–96% weed biomass reduction and 61‒79% weed density reductions compared with the nontreated control. Herbicides applied post‐emergence (POST; dicamba plus glyphosate, glyphosate, glufosinate, and acetochlor plus clethodim plus lactofen) provided 93–99% control of all weed species 28 d after POST (DAPOST). Herbicides applied POST provided 89–98% weed biomass reduction and 86–96% density reduction at 28 DAPOST. For individual site‐years, yield was often similar for PRE followed by POST herbicide programs in herbicide‐resistant (HR) and conventional soybean. Gross profit margins and benefit/cost ratios were higher in HR soybean than in conventional soybean, although price premiums for conventional soybean can help compensate for increased herbicide costs.

Globally, rationalizing and converting each drop of irrigation water into food is a crucial act in agricultural production, particularly with climatic change concerns. Thus, the current study seeks to find an integral practice between irrigation pattern and weed control for saving the irrigation water in peanut fields with improving the nutritional value of the seeds. In sandy loam soil, under two irrigation regimes (75 and 100% of crop evapotranspiration—ETc75 and ETc100, respectively), the responses of peanut pod yield and quality (seed oil, N, P, and K contents) and water use efficiency to six weed control treatments (bentazon, clethodim, bentazon + hoeing once,clethodim + hoeing once, hoeing twice and unweeded) were evaluated. The obtained data of 2016 and 2017 seasons illustrated that whether using ETc75 or ETc100, hoeing twice showed the highest efficiency of weed control in peanut. Reduction in yield was diminished from 15.1–16.9% in unweeded plots to 9.0–9.7% in weeded ones. Controlling weeds led to a decrease in their efficiency for exploiting the applied water. That decrease amounted to 64.4 and 64.3% reductions with ETc100 as well as 66.9 and 64.4% reductions with ETc75 in the 1st and 2nd seasons, respectively. Peanut plants consumed less water under ETc75 than ETc100 to produce one kilogram of pods by about 17.9% in weeded plots (mean of applied weeded treatments) as well as 10.1% in weedy conditions. Also, ETc75 plus weeded practices raised the benefit/cost by 52.3% compared to unweeded one. In conclusion, the interactional impact of irrigation and weed control proved that peanut plants can be irrigated as much as 75% of evapotranspiration under water shortage conditions with hoeing twice or herbicide use. Selecting the appropriate weed control practice is a vital act for water saving and keeping productivity, quality and returns of peanut cultivation in arid regions.

Volunteer corn is often overlooked as a weed in soybean. To aid in management decisions, this study determined soybean yield loss attributed to volunteer corn and efficacy of various herbicides at several rates and timings. A hyperbolic equation estimated (R2 = 0.88) incremental yield loss (I) of 39.7% at low density when maximum yield loss (A) was constrained to 71%, the highest yield loss observed in these trials, revealing a more competitive plant than many common midwestern weedy species. Clethodim applied at 51 g ai ha−1 at V4 soybean resulted in > 90% volunteer corn control with < 5% soybean yield loss, whereas if applied at 12.7 g ai ha−1 volunteer corn control was 15%, but soybean yield was 50% greater than the nontreated control. On the basis of these data, the partial volunteer corn control improved soybean yield. Timing of glufosinate application influenced volunteer corn control. Glufosinate applied to 15-cm-tall corn resulted in 33% control, whereas applications to 36- to 91-cm corn resulted in > 70% control. Glufosinate combined with grass herbicides improved control to > 85%, with concomitant yield increases. Results demonstrated that volunteer corn substantially reduced soybean yield at low densities and yield increased when volunteer corn was controlled with various herbicides. On the basis of these results, and current soybean grain and herbicide prices, soybean yield gains from volunteer corn control could increase net return by > $150 ha−1. Nomenclature: Clethodim; glufosinate; glyphosate; quizalofop; corn, Zea mays L.; soybean, Glycine max (L.) Merr. El maíz voluntario es frecuentemente ignorado como una maleza en campos de soja. Para ayudar a la toma de decisiones de manejo, este estudio determinó la pérdida de rendimiento atribuida al maíz voluntario y la eficacia de varios herbicidas a varias dosis y momentos de aplicación. Una ecuación hiperbólica estimó (R2 = 0.88) pérdidas de rendimiento incrementales (I) de 39.7% a densidades bajas cuando la pérdida máxima de rendimiento se limitó a 71%, la cual fue la pérdida de rendimiento más alta observada en estos ensayos, lo que reveló que el maíz voluntario es una planta más competitiva que muchas especies de malezas comúnmente observadas en el medio oeste. Clethodim aplicado a 51 g ai ha−1 durante el estadio V4 de la soja resultó en >90% de control de maíz voluntario con <5% de pérdidas en el rendimiento de la soja, mientras que si se aplicó a 12.7 g ai ha−1 el control del maíz voluntario fue 15%, pero el rendimiento de la soja fue 50% mayor que el de control sin tratamiento. Con base en estos datos, el control parcial del maíz voluntario mejoró el rendimiento de la soja. El momento de aplicación de glufosinate influyó en el control del maíz voluntario. Glufosinate aplicado a plantas de maíz de 15 cm de altura resultó en 33% de control, mientras que aplicaciones a maíz de 36 a 91 cm de altura resultó en >70% de control. Glufosinate combinado con herbicidas para gramíneas mejoraron el control a >85%, con incrementos concomitantes de rendimiento. Los resultados demostraron que el maíz voluntario redujo sustancialmente el rendimiento de la soja a bajas densidades y el rendimiento incrementó cuando el maíz voluntario fue controlado con varios herbicidas. Con base en estos resultados y los precios actuales de grano de soja y de herbicidas, las ganancias en el rendimiento de la soja producto del control del maíz voluntario pudo incrementar la rentabilidad neta en >$150 ha−1.