Matthew D. Jeffries

Arsenic Retention in Foliage and Soil after Monosodium Methyl Arsenate (MSMA) Application to Turfgrass.

Monosodium methyl arsenate (MSMA) is a commonly used herbicide for weed control in turfgrass systems. There is concern that arsenic from applied MSMA could leach to groundwater or run off into surface water, thereby threatening human and ecosystem health. The USEPA has proposed a phase-out of the herbicide but is seeking additional research about the toxicity and environmental impacts of MSMA before establishing a final ruling. Little research has systematically investigated MSMA in field-based settings; instead, risks have been inferred from isolated field measurements or model-system studies. Accordingly, the overall goal of this study was to quantify the fate of arsenic after MSMA application to a managed turfgrass system. After MSMA application to turfgrass-covered and bareground lysimeters, the majority of arsenic was retained in turfgrass foliage and soils throughout year-long experiments, with 50 to 101% of the applied arsenic recovered in turfgrass systems and 55 to 66% recovered in bareground systems. Dissolved arsenic concentrations from 76.2-cm-depth pore water in the MSMA-treated soils were consistently <2 μg L, indistinguishable from background concentrations. As measured by adsorption isotherm experiments, MSMA retention by the sandy soil from our field site was markedly less than retention by a washed sand and a clay loam. Collectively, these results suggest that under aerobic conditions, minimal arsenic leaching to groundwater would occur after a typical application of MSMA to turfgrass. However, repeated MSMA application may pose environmental risks. Additional work is needed to examine arsenic cycling near the soil surface and to define arsenic speciation changes under different soil conditions.

Annual Bluegrass (Poa annua) Control in Creeping Bentgrass Putting Greens with Amicarbazone and Paclobutrazol

Abstract Amicarbazone is a photosystem II–inhibiting herbicide recently registered for annual bluegrass control in established turf systems that include creeping bentgrass. However, research to date reveals potential issues with creeping bentgrass tolerance to amicarbazone. Currently, the plant-growth regulator paclobutrazol is widely adopted by turf managers for chemical annual bluegrass suppression in creeping bentgrass putting greens. Field experiments were conducted throughout North Carolina in the spring of 2010 and 2011 to assess treatment regimens that included amicarbazone (49, 65, or 92 g ai ha−1) and paclobutrazol (70, 140, or 280 g ai ha−1) applied alone, as tank-mixtures, or used in tandem, at varying rates and sequential timings for annual bluegrass control in creeping bentgrass putting greens. In general, regimens including both compounds provided greater annual bluegrass control and acceptable turfgrass tolerance compared with stand-alone applications of amicarbazone at 8 and 12 wk after initial treatment (WAIT). When comparing regimens that included amicarbazone at 49 or 65 g ha−1, creeping bentgrass tolerance was greater for the higher application rate applied less frequently. These results indicate amicarbazone usage on creeping bentgrass greens may be beneficially affected with the incorporation of paclobutrazol to treatment regimens because annual bluegrass control with the combination was equal to or greater than stand-alone amicarbazone applications, and creeping bentgrass tolerance was superior 8 and 12 WAIT. Nomenclature: Amicarbazone; paclobutrazol; annual bluegrass; Poa annua L.; creeping bentgrass; Agrostis stolonifera L. Resumen Amicarbazone es un herbicida inhibidor del fotosistema II que fue recientemente registrado para el control de Poa annua en sistemas de céspedes establecidos incluyendo Agrostis stolonifera. Sin embargo, la investigación hasta la fecha revela problemas potenciales con la tolerancia de A. stolonifera a amicarbazone. Actualmente, el regulador de crecimiento paclobutrazol es ampliamente adoptado por especialistas en céspedes para la supresión química de P. annua en putting greens de A. stolonifera. Experimentos de campo fueron realizados en North Carolina en la primavera de 2010 y 2011 para evaluar regímenes con tratamientos que incluyeron amicarbazone (49, 65, ó 92 g ai ha−1) y paclobutrazol (70, 140, ó 280 g ai ha−1), aplicados solos o en mezcla en tanque, o usados en tándem, a dosis variables y en aplicaciones secuenciales para el control de P. annua en putting greens de A. stolonifera. En general, los regímenes que incluyeron ambos compuestos brindaron un mayor control de P. annua y una tolerancia aceptable del césped en comparación con aplicaciones solas de amicarbazone a 8 y 12 semanas después del tratamiento inicial (WAIT). Cuando se compararon regímenes que incluyeron amicarbazone a 49 ó 65 g ha−1, la tolerancia del césped fue mayor cuando las dosis más altas fueron aplicadas en menor frecuencia. Estos resultados indican que el uso de amicarbazone en greens de A. stolonifera podría ser afectado beneficiosamente con la incorporación de paclobutrazol porque el control de P. annua con la combinación fue igual o mayor que las aplicaciones solas de amicarbazone, y la tolerancia del césped fue superior a 8 y 12 WAIT.

Management considerations to minimize environmental impacts of arsenic following monosodium methylarsenate (MSMA) applications to turfgrass.

Monosodium methylarsenate (MSMA) is an organic arsenical herbicide currently utilized in turfgrass and cotton systems. In recent years, concerns over adverse impacts of arsenic (As) from MSMA applications have emerged; however, little research has been conducted in controlled field experiments using typical management practices. To address this knowledge gap, a field lysimeter experiment was conducted during 2012-2013 to determine the fate of As following MSMA applications to a bareground and an established turfgrass system. Arsenic concentrations in soil, porewater, and aboveground vegetation, were measured through one yr after treatment. Aboveground vegetation As concentration was increased compared to nontreated through 120 d after initial treatment (DAIT). In both systems, increased soil As concentrations were observed at 0-4 cm at 30 and 120 DAIT and 0-8 cm at 60 and 365 DAIT, suggesting that As was bound in shallow soil depths. Porewater As concentrations in MSMA-treated lysimeters from a 30-cm depth (22.0-83.8 μg L(-1)) were greater than those at 76-cm depth (0.4-5.1 μg L(-1)). These results were combined with previous research to devise management considerations in systems where MSMA is utilized. MSMA should not be applied if rainfall is forecasted within 7 DAIT and/or in areas with shallow water tables. Further, disposing of MSMA-treated turfgrass aboveground vegetation in a confined area - a common management practice for turfgrass clippings - may be of concern due to As release to surface water or groundwater as the vegetation decomposes. Finally, long-term MSMA use may cause soil As accumulation and thus downward migration of As over time; therefore, MSMA should be used in rotation with other herbicides.

Mitigation Practices to Effectively Overseed into Indaziflam-Treated Turfgrass Areas

Indaziflam is a PRE herbicide for annual broadleaf and grass control in turfgrass systems and requires a 40-wk minimum interval between application and overseeding perennial ryegrass. Currently, activated-charcoal application is recommended to reduce that interval; however, preliminary evaluations determined activated charcoal alone was not a robust mitigation practice for successful establishment during perennial ryegrass overseeding. Field research was conducted in North Carolina and Tennessee to evaluate various mitigation practices to effectively overseed perennial ryegrass into indaziflam-treated turfgrass areas. Immediately following indaziflam application (53 g ai ha−1), two scenarios were created by delivering 0 or 0.3 cm H2O before mitigation practice. Irrigated plots were air-dried before conducting mitigation practices. Evaluated mitigation practices included scalping (0.6 cm cut height; debris removed), verticutting (1.25 cm depth; debris removed), and activated-charcoal application (167 kg ha−1 applied as an aqueous slurry in 3,180 L ha−1), evaluated individually and in each two-way combination in the order scalp followed by (fb) activated charcoal, scalp fb verticut, or verticut fb activated charcoal. Twenty-four hours after mitigation practice completion, perennial ryegrass was seeded (976 kg ha−1) and maintained as a golf course fairway. Overall, perennial ryegrass cover was reduced ≥ 93% at 8 and 20 wk after treatment (WAT) when no mitigation practices were performed. Stand-alone mitigation practices variably improved perennial ryegrass establishment; however, no practice provided acceptable results for end users. Combining mitigation practices improved overseeding establishment, most notably by adding activated charcoal application or verticutting to scalping before irrigation. Across experimental runs and locations, scalp fb activated-charcoal application before irrigation reduced perennial ryegrass cover 22 to 27% at 20 WAT. Results from this research suggest mitigation practices in addition to the currently recommended activated-charcoal application should be performed by turfgrass managers to improve perennial ryegrass overseeding establishment in indaziflam-treated turfgrass areas. Nomenclature: Indaziflam; bermudagrass, Cynodon dactylon (L.) Pers.; hybrid bermudagrass × African dogstooth grass, Cynodon dactylon (L.) × Cynodon transvaalensis Burtt Davy; perennial ryegrass, Lolium perenne L. Indaziflam es un herbicida PRE para el control de gramíneas anuales en sistemas de céspedes y que requiere un intervalo mínimo de 40 semanas entre la aplicación y la siembra de Lolium perenne sobre césped bermuda establecido. Actualmente, la aplicación de carbón activado está recomendada para reducir este intervalo; sin embargo, evaluaciones preliminares permitieron determinar que el carbón activado solo no fue una práctica robusta para el establecimiento exitoso durante la siembra de L. perenne sobre césped establecido. Se realizó una investigación de campo en North Carolina y Tennessee para evaluar varias práctica de mitigación, para poder sembrar efectivamente L. perenne en áreas de césped tratadas con indaziflam. Inmediatamente después de la aplicación de indaziflam (53 g ai ha−1), se crearon dos escenarios aplicando 0 ó 0.3 cm H2O antes de la práctica de mitigación. Las parcelas irrigadas se dejaron secar al aire antes de realizar las prácticas de mitigación. Las prácticas de mitigación evaluadas incluyeron la remoción de la mayoría del tejido foliar (scalp; corte a 0.6 cm de altura y remoción de residuos), corte vertical (verticut; corte a 1.25 cm de profundidad y remoción de residuos), y la aplicación de carbón activado (167 kg ha−1 aplicado como una suspensión acuosa en 3,180 L ha−1), evaluados individualmente y en cada una de las posibles combinaciones en pares, en el orden de scalp seguido por (fb) carbón activado, scalp fb verticut, o verticut fb carbón activado. Veinticuatro horas después de terminar la práctica de mitigación, se sembró L. perenne (976 kg ha−1) y el área se mantuvo como fairway de un campo de golf. En general, la cobertura de L. perenne se redujo ≥93% entre 8 y 20 semanas después del tratamiento (WAT) cuando no había práctica de mitigación. Las prácticas de mitigación consideradas en forma independiente, mejoraron el establecimiento de L. perenne en forma variable. Sin embargo, ninguna práctica brindó resultados aceptables para los usuarios finales. El combinar las prácticas de mitigación mejoró el establecimiento de L. perenne, y esto fue más notable al agregar la aplicación de carbón activado o verticut a áreas con scalp antes del riego. Al analizar en forma conjunta las corridas experimentales y las localidades, scalp fb carbón activado antes del riego redujo la cobertura de L. perenne 22 a 27% a 20 WAT. Los resultados de esta investigación sugieren que las prácticas de mitigación, además de las aplicaciones de carbón activado, actualmente recomendadas, deberían ser implementadas por profesionales de manejo de césped para mejorar el proceso de establecimiento en áreas de césped tratadas con indaziflam.

Factors Influencing Dislodgeable 2, 4-D Plant Residues from Hybrid Bermudagrass (Cynodon dactylon L. x C. transvaalensis) Athletic Fields.

Research to date has confirmed 2,4-D residues may dislodge from turfgrass; however, experiments have not been conducted on hybrid bermudagrass (Cynodon dactylon L. x C. transvaalensis), the most common athletic field turfgrass in subtropical climates. More specifically, previous research has not investigated the effect of post-application irrigation on dislodgeable 2,4-D residues from hybrid bermudagrass and across turfgrass species, research has been nondescript regarding sample time within a d (TWD) or conducted in the afternoon when the turfgrass canopy is dry, possibly underestimating potential for dislodgement. The effect of irrigation and TWD on 2,4-D dislodgeability was investigated. Dislodgeable 2,4-D amine was reduced > 300% following irrigation. From 2 to 7 d after treatment (DAT), ≤ 0.5% of applied 2,4-D was dislodged from irrigated turfgrass, while ≤ 2.3% of applied 2,4-D was dislodged when not irrigated. 2,4-D dislodgeability decreased as TWD increased. Dislodgeable 2,4-D residues declined to < 0.1% of the applied at 1 DAT– 13:00, and increased to 1 to 3% of the applied 2 DAT– 5:00, suggesting 2,4-D re-suspended on treated turfgrass vegetation overnight. In conclusion, irrigating treated turfgrass reduced dislodgeable 2,4-D. 2,4-D dislodgeability increased as TWD decreased, which was attributed to non-precipitation climatic conditions favoring turfgrass canopy wetness. This research will improve turfgrass management practices and research designed to minimize human 2,4-D exposure.

Comparing Dislodgeable 2,4-D Residues across Athletic Field Turfgrass Species and Time.

2,4-dimethylamine salt (2,4-D) is an herbicide commonly applied on athletic fields for broadleaf weed control that can dislodge from treated turfgrass. Dislodge potential is affected by numerous factors, including turfgrass canopy conditions. Building on previous research confirming herbicide-turfgrass dynamics can vary widely between species, field research was initiated in 2014 and 2015 in Raleigh, NC, USA to quantify dislodgeable 2,4-D residues from dormant hybrid bermudagrass (Cynodon dactylon L. x C. transvaalensis) and hybrid bermudagrass overseeded with perennial ryegrass (Lolium perenne L.), which are common athletic field playing surfaces in subtropical climates. Additionally, dislodgeable 2,4-D was compared at AM (7:00 eastern standard time) and PM (14:00) sample timings within a day. Samples collected from perennial ryegrass consistently resulted in greater 2,4-D dislodgment immediately after application (9.4 to 9.9% of applied) compared to dormant hybrid bermudagrass (2.3 to 2.9%), as well as at all AM compared to PM timings from 1 to 3 d after treatment (DAT; 0.4 to 6.3% compared to 0.1 to 0.8%). Dislodgeable 2,4-D did not differ across turfgrass species at PM sample collections, with ≤ 0.1% of the 2,4-D applied dislodged from 1 to 6 DAT, and 2,4-D detection did not occur at 12 and 24 DAT. In conclusion, dislodgeable 2,4-D from treated turfgrass can vary between species and over short time-scales within a day. This information should be taken into account in human exposure risk assessments, as well as by turfgrass managers and athletic field event coordinators to minimize 2,4-D exposure.

Persistence and Bioavailability of Aminocyclopyrachlor and Clopyralid in Turfgrass Clippings: Recycling Clippings for Additional Weed Control

Abstract The synthetic auxin herbicides, aminocyclopyrachlor and clopyralid, control dicotyledonous weeds in turf. Clippings of turfgrass treated with synthetic auxin herbicides have injured off-target plants exposed to herbicide-laden clippings. Labels of aminocyclopyrachlor and clopyralid recommend that clippings of treated turfgrass remain on the turf following a mowing event. Alternative uses for synthetic auxin-treated turfgrass clippings are needed because large quantities of clippings on the turf surface interfere with the functionality and aesthetics of golf courses, athletic fields, and residential turf. A white clover bioassay was conducted to determine the persistence and bioavailability of aminocyclopyrachlor and clopyralid in turfgrass clippings. Aminocyclopyrachlor and clopyralid were each applied at 79 g ae ha−1 to mature tall fescue at 56, 28, 14, 7, 3.5, and 1.75 d before clipping collection (DBCC). Clippings were collected, and the treated clippings were recycled onto adjacent white clover plots to determine herbicidal persistence and potential for additional weed control. Clippings of tall fescue treated with aminocyclopyrachlor produced a nonlinear regression pattern of response on white clover. Calculated values for 50% response (GR50) for visual control, for normalized difference vegetative index (NDVI), and for reduction in harvested biomass were 20.5, 17.3, and 18.7 DBCC, respectively, 8 wk after clippings were applied. Clippings of tall fescue treated with clopyralid did not demonstrate a significant pattern for white clover control, presumably because clopyralid was applied at a less-than-label rate. The persistence and bioavailability of synthetic auxin herbicides in clippings harvested from previously treated turfgrass creates the opportunity to recycle clippings for additional weed control. Nomenclature: Aminocyclopyrachlor; clopyralid; tall fescue, Lolium arundinaceum (Schreb.) S.J. Darbyshire; white clover, Trifolium repens L. ‘Dutch’.

Effect of Soil Organic Matter Content and Volumetric Water Content on ‘Tifway 419’ Hybrid Bermudagrass Growth Following Indaziflam Applications

Indaziflam is a cellulose biosynthesis–inhibiting herbicide for PRE annual weed control in turfgrass systems. Since indaziflams 2010 U.S. registration, sporadic cases of hybrid bermudagrass injury have been reported; however, causes are not well understood. Field research was conducted from 2013 to 2015 on sandy soil to elucidate the effects of soil organic matter content (SOMC) and soil volumetric water content (SVWC) on plant growth following indaziflam application on established or root-compromised (5 cm long) hybrid bermudagrass. The effect of SOMC was evaluated at two levels, 1.4 (low) and 5.5% (high) w/w at the soil surface (0 to 2.5 cm depth), whereas SVWC was evaluated PRE (2 wk before) and POST (6 wk after) indaziflam application at two levels (low or high). Indaziflam was applied (50 or 100 g ai ha−1) at fall-only, fall-plus-spring, and spring-only timings. Regardless of application timing or SVWC, indaziflam applied at 50 g ha−1 to high SOMC did not cause > 10% visual cover reduction on established or root-compromised hybrid bermudagrass. Indaziflam applied to hybrid bermudagrass on low SOMC exacerbated adverse growth effects, most notably when root systems were compromised before application. Overall, PRE indaziflam application SVWC did not affect hybrid bermudagrass growth. Within low SOMC, low POST indaziflam application SVWC caused less visual hybrid bermudagrass cover reduction than did high POST indaziflam application SVWC, whereas both fall-plus-spring and spring-only application timings caused similarly greater reductions than fall-only indaziflam application. Data from this research will aid turfgrass managers to effectively use indaziflam without adversely affecting hybrid bermudagrass growth. Nomenclature: Indaziflam; hybrid bermudagrass, Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davey ‘Tifway 419’. Indaziflam es un herbicida inhibidor de la biosíntesis de cellulose para el control PRE de malezas anuales en sistemas de céspedes. Desde el registro de indaziflam en Estados Unidos en 2010, se han reportado casos esporádicos de daño en el césped bermuda híbrido, aunque las causas no se conocen bien. Entre 2013 y 2015, se realizó una investigación de campo en un suelo arenoso, para elucidar los efectos del contenido de materia orgánica del suelo (SOMC) y el contenido volumétrico de agua del suelo (SVWC) sobre el crecimiento vegetal después de la aplicación de indaziflam a un césped bermuda híbrido establecido o con un sistema radicular comprometido (5 cm de largo). El efecto de SOMC fue evaluado a dos niveles, 1.4 (bajo) y 5.5% (alto) peso/peso, en la superficie del suelo (0 a 2.5 cm de profundidad), mientras que SVWC fue evaluado antes (2 semanas antes) y después (6 semanas después) de la aplicación de indaziflam a dos niveles (bajo o alto). Indaziflam fue aplicado (50 ó 100 g ai ha−1) solamente en el otoño, el otoño más la primavera, y solamente la primavera. Sin importar el momento de aplicación o SVWC, indaziflam aplicado a 50 g ha−1 a alto SOMC no causó >10% de reducción en la cobertura estimada visualmente en césped bermuda híbrido establecido o con raíces comprometidas. Indaziflam aplicado a césped bermuda híbrido con bajo SOMC exacerbó los efectos adversos en el crecimiento, más notablemente cuando los sistemas radiculares estuvieron comprometidos antes de la aplicación. En general, la aplicación PRE de indaziflam según SVWC no afectó el crecimiento del césped bermuda híbrido. Con bajo SOMC, la aplicación de indaziflam POST con bajo SVWC causó menos reducción en la cobertura estimada visualmente del césped bermuda híbrido que la aplicación POST de indaziflam con alto SVWC, mientras que los momentos de aplicación en el otoño más la primavera y solamente en la primavera causaron mayores reducciones (similares entre ellos) que la aplicación solamente en el otoño. Los datos de esta investigación ayudarán a los profesionales en céspedes para usar efectivamente indaziflam sin afectar adversamente el crecimiento del césped bermuda híbrido.

Effect of Selective Amicarbazone Placement on Annual Bluegrass (Poa annua) and Creeping Bentgrass Growth

Abstract Growth chamber experiments were conducted to assess the effects of foliage-only, soil-only, and foliage-plus-soil placements of amicarbazone on annual bluegrass and creeping bentgrass growth. Evaluated herbicide treatments included amicarbazone at 49 or 147 g ai ha−1, as well as bispyribac-sodium at 74 g ai ha−1 for comparative purposes. Data from this research agree with previous reports of amicarbazone plant uptake. Amicarbazone is absorbed via above- and belowground pathways; however, plant growth is inhibited more by root uptake. Compared to foliage-only amicarbazone placement, soil-only placement more than doubled reductions in aboveground biomass and root mass 56 d after treatment (DAT), whereas no differences were detected between placements including soil contact. Across all evaluated parameters in this research, amicarbazone (49 g ha−1) impacted creeping bentgrass growth similarly to bispyribac-sodium, whereas annual bluegrass growth was inhibited more by amicarbazone, suggesting it provides a more efficacious chemical option for end-user applications. Nomenclature: Amicarbazone; bispyribac-sodium; annual bluegrass; Poa annua L. var. annua; creeping bentgrass; Agrostis stolonifera L. ‘Penn A1’. Resumen Se realizaron experimentos en cámaras de crecimiento para evaluar los efectos de aplicar amicarbazone solamente en el follaje, solamente en el suelo y en el follaje más el suelo, sobre el crecimiento de Poa annua y Agrostis stolonifera. Los tratamientos de herbicidas evaluados incluyeron amicarbazone a 49 ó 147 g ai ha−1, y bispyribac-sodium a 74 g ai ha−1 para fines de comparación. Los datos de esta investigación concordaron con reportes previos sobre la absorción de amicarbazone, porque este compuesto es absorbido por vías por encima y debajo del suelo. Sin embargo, el crecimiento vegetal es inhibido más cuando la absorción se da por la raíz. Al compararse con la localización foliar del amicarbazone, la localización solamente en el suelo redujo la biomasa aérea y de raíz en más del doble a 56 días después del tratamiento (DAT), mientras que no se detectaron diferencias entre tratamientos que incluyeron contacto con el suelo. A lo largo de todos los parámetros evaluados en esta investigación, amicarbazone (49 g ha−1) impactó el crecimiento de A. stolonifera en forma similar a bispyribac-sodium, mientras que el crecimiento de P. annua fue inhibido más por amicarbazone, lo que sugiere que este herbicida provee una opción química eficaz de control para los usuarios.

Herbicide Inputs and Mowing Affect Vaseygrass (Paspalum urvillei) Control

Vaseygrass is an invasive, perennial C4-grass commonly found on roadsides in areas with poorly drained soils. Due to its upright growth habit and seedhead production, vaseygrass can impair motorist sightlines and subsequently, require increased management inputs to maintain vegetation at an acceptable height. Two field experiments were conducted from 2012 to 2015 on North Carolina roadsides to evaluate the effect of mowing and mowing timing with respect to applications of various herbicides on vaseygrass control. Both experiments evaluated clethodim (280 g ai ha−1), foramsulfuron+halosulfuron+thiencarbazone-methyl (44+69+22 g ai ha−1), imazapic (140 g ai ha−1), metsulfuron+nicosulfuron (16+59 g ai ha−1), and sulfosulfuron (105 g ai ha−1) with a nonionic surfactant at 0.25% v/v. Experiment one focused on the effect of mowing (routinely mowed or nonmowed) and herbicide application timing (fall-only, fall-plus-spring, or spring-only), while experiment two focused on pre-herbicide application mowing intervals (6, 4, 3, 2, 1, or 0 wk before treatment [WBT]). From experiment one, routine mowing reduced vaseygrass cover in nontreated plots 55% at 52 wk after fall treatment (WAFT), suggesting this cultural practice should be employed where possible. Additionally, routine mowing and herbicide application season affected herbicide efficacy. Treatments providing >70% vaseygrass cover reduction at 52 WAFT included routinely mowed fall-only clethodim and fall-plus-spring imazapic, and fall-plus-spring metsulfuron+nicosulfuron across mowing regimens. Within clethodim, mowing vaseygrass 2 or 1 WBT resulted in the lowest cover at 40 (1 to 2%) and 52 (4 to 6%) wk after treatment (WAT) compared to other intervals, which aligns with current label vegetation height at treatment recommendation. Vaseygrass persisted across all treatments evaluated through 52 WAT, suggesting eradication of this species will require inputs over multiple growing seasons. Nomenclature: Clethodim; foramsulfuron; halosulfuron; imazapic; metsulfuron; nicosulfuron; sulfosulfuron; thiencarbazone; vaseygrass, Paspalum urvillei Steud. Paspalum urvillei es una gramínea C4 perenne invasiva que se encuentra comúnmente a las orillas de caminos y en áreas con suelos con poco drenaje. Debido a su hábito de crecimiento vertical y producción de espigas, P. urvillei puede limitar la visibilidad de vehículos y subsecuentemente incrementar los insumos de manejo para mantener la vegetación a una altura aceptable. Se realizaron dos experimentos de campo desde 2012 a 2015 en orillas de caminos en North Carolina para evaluar los efectos de la chapia y el momento de chapia con respecto a las aplicaciones de varios herbicidas sobre el control de P. urvillei. Ambos experimentos evaluaron clethodim (280 g ai ha−1), foramsulfuron+halosulfuron+thiencarbazone-methyl (44+69+22 g ai ha−1), imazapic (140 g ai ha−1), metsulfuron+nicosulfuron (16+59 g ai ha−1), y sulfosulfuron (105 g ai ha−1) con un surfactante no iónico a 0,25% v/v. El experimento uno se enfocó en el efecto de la chapia (chapia rutinaria o sin chapia) y el momento de aplicación de herbicidas (sólo otoño, otoño más primavera, o sólo primavera), mientras que el experimento dos se enfocó en el intervalo entre la chapia y la aplicación de herbicidas (6, 4, 3, 2, 1, ó 0 semanas antes del tratamiento [WBT]). En el experimento uno, la chapia rutinaria redujo 55%la cobertura de P. urvillei en parcelas sin tratamiento con herbicidas a 52 semanas después del tratamiento de otoño (WAFT), sugiriendo que esta práctica cultural debería ser empleada cuando sea posible. Adicionalmente, la chapia rutinaria y la temporada de aplicación de herbicida afectaron la eficacia del herbicida. Los tratamientos que proveyeron >70% de reducción en la cobertura de P. urvillei a 52 WAFT incluyeron chapia rutinaria y clethodim sólo en el otoño e imazapic en el otoño más la primavera, y metsulfuron+nicosulfuron en el otoño más la primavera para todos los regímenes de chapia. Dentro de los tratamientos con clethodim, la chapia 2 ó 1 WBT resultó en la menor cobertura a 40 (1 a 2%) y 52 (4 a 6%) semanas después del tratamiento (WAT) al compararse con otros intervalos, lo que se alinea con la actual recomendación de la etiqueta de tratamiento según la altura de la vegetación. P. urvillei persistió en todos los tratamientos evaluados hasta 52 WAT, lo que sugiere que la erradicación de esta especie requerirá insumos a lo largo de múltiples temporadas de crecimiento.