Gerald M. Henry

PRE and POST Control of Annual Bluegrass (Poa annua) with Indaziflam

Abstract Indaziflam controls annual grassy weeds by inhibiting cellulose biosynthesis. Research was conducted from 2008 to 2011 in Tennessee, Texas, and Georgia evaluating the efficacy of indaziflam for PRE and POST control of annual bluegrass in bermudagrass turf. In Texas, indaziflam at 30, 40, 50, and 60 g ai ha−1 applied PRE provided 93 to 100% annual bluegrass control through 28 wk after treatment. When applied PRE at 80 g ai ha−1 and at 4, 8, and 12 wk after PRE (WAP), indaziflam controlled annual bluegrass 67 to 100% 32 wk after initial treatment (WAIT) in Tennessee; however, reduced efficacy was observed with 12 WAP treatments in a single year of a 2-yr study. Similarly, annual bluegrass control with PRE applications or with 4 and 8 WAP applications of indaziflam at 35 and 52.5 g ai ha−1 ranged from 88 to 100% at 30 WAIT in Tennessee. In Georgia, these rates of indaziflam applied PRE and 4 WAP controlled annual bluegrass 96 to 100% on all evaluation dates and resulted in 97 to 100% reduction in plant counts relative to the untreated control at 30 WAIT. When applied 8 WAP, the 35 and 52.5 g ai ha−1 rates of indaziflam controlled annual bluegrass only 51 to 71% at 30 WAIT in Georgia. Although increasing the application rate of indaziflam treatments 8 WAP provided greater annual bluegrass control, each rate provided significantly lower control when applied 8 WAP compared with PRE or at 4 WAP. No bermudagrass injury was observed in this research. Results suggest indaziflam provides effective PRE and early POST control of annual bluegrass in bermudagrass turf. However, additional research is needed to determine the effects of plant size and maturity on indaziflam efficacy for POST annual bluegrass control. Nomenclature: Annual bluegrass, Poa annua L.; bermudagrass, Cynodon dactylon (L.) Pers.

Methiozolin efficacy for annual bluegrass (Poa annua) control on sand- and soil-based creeping bentgrass putting greens.

Abstract Methiozolin is a new isoxazoline herbicide being investigated for selective POST annual bluegrass control in creeping bentgrass putting greens. Glasshouse and field research was conducted from 2010 to 2012 in Tennessee and Texas to evaluate annual bluegrass control efficacy with methiozolin. Application placement experiments in the glasshouse illustrated that root absorption was required for POST annual bluegrass control with methiozolin at 1,000 g ai ha−1. Soil-plus-foliar and soil-only applications of methiozolin reduced annual bluegrass biomass greater than treatments applied foliar-only. Field experiments evaluated annual bluegrass control efficacy with two application rates (500 and 1,000 g ha−1) and six application regimes (October, November, December, October followed by [fb] November, November fb December, and October fb November fb December) on sand- and soil-based putting greens. Annual bluegrass control with methiozolin at 1,000 g ha−1 on sand-based greens ranged from 70 to 72% compared to 87 to 89% on soil-based greens. Treatment at 500 g ha−1 controlled annual bluegrass 57 to 64% on sand-based greens compared to 72 to 80% on soil-based greens. Most sequential methiozolin application regimes controlled annual bluegrass more than single applications. On sand-based greens, sequential application programs controlled annual bluegrass 70 to 79% compared to 85 to 92% on soil-based greens. Responses indicate that methiozolin is a root-absorbed herbicide with efficacy for selective control of annual bluegrass in both sand- and soil-based creeping bentgrass putting greens. Nomenclature: Methiozolin [5-(2,6-difluorobenzyl) oxymethyl-5-methyl-3-(3methylthiophen-2-yl)-1,2-isoxazoline]; annual bluegrass, Poa annua L.; creeping bentgrass, Agrostis stolonifera L. Resumen Methiozolin es un herbicida isoxazoline nuevo que está siendo investigado para el control selectivo POST de Poa annua en “putting greens” del césped Agrostis stolonifera. Se realizaron investigaciones de invernadero y de campo desde 2010 a 2012, en Tennessee y Texas, para evaluar la eficacia de methiozolin en el control de P. annua. En el invernadero, experimentos de localización de la aplicación ilustraron que la absorción por la raíz fue requerida para el control POST de P. annua con methiozolin a 1,000 g ai ha−1. Aplicaciones de methiozolin al suelo y al follaje o solamente al suelo redujeron la biomasa de P. annua más que los tratamientos con aplicaciones solamente foliares. Los experimentos de campo evaluaron la eficacia en el control de P. annua con dos dosis de aplicación (500 y 1,000 g ha−1) y seis regímenes de aplicación (Octubre, Noviembre, Diciembre, Octubre seguido de (fb) Noviembre, Noviembre fb Diciembre, y Octubre fb Noviembre fb Diciembre) en putting greens en arena y en suelo. El control de P. annua con methiozolin a 1,000 g ha−1 en greens en arena varió entre 70 y 72% comparado con 87 a 89% en greens en suelo. Los tratamientos con 500 g ha−1 controlaron P. annua 57 a 64% en greens en arena, comparados con 72 a 80% en greens en suelo. La mayoría de los regímenes secuenciales de aplicación de methiozolin controlaron P. annua más que las aplicaciones individuales. En greens en arena, los programas de aplicaciones secuenciales controlaron P. annua 70 a 79% comparados con 85 a 92% en greens en suelo. Las respuestas indican que methiozolin es un herbicida absorbido por la raíz con eficacia para el control selectivo de P. annua en putting greens de A. stolonifera tanto en arena como en suelo.

Response of Miscanthus × giganteus and Miscanthus sinensis to postemergence herbicides.

Abstract Studies were conducted under greenhouse conditions at Michigan State University and Texas Tech University to investigate the tolerance of Miscanthus × giganteus and Miscanthus sinensis to POST herbicides. Miscanthus sinensis and M. × giganteus were treated with 10 and 18 POST herbicide treatments, respectively. Plants were evaluated for injury as well as dry aboveground and belowground biomass production 28 days after treatment. Imazethapyr at 0.069 kg ai ha−1 caused 5% injury to M. sinensis, which was greater than the nontreated check. Imazethapyr, imazamox at 0.044 kg ai ha−1, and rimsulfuron at 0.017 kg ai ha−1 reduced aboveground biomass of M. sinensis compared with the nontreated check. Dicamba at 0.56 kg ai ha−1 and halosulfuron at 0.035 kg ai ha−1 resulted in M. sinensis aboveground biomass similar to the nontreated check. Injury exhibited by M. × giganteus was greater than the nontreated check with glyphosate at 0.84 kg ae ha−1 (54%), foramsulfuron at 0.037 kg ai ha−1 (32%), nicosulfuron at 0.035 kg ai ha−1 (28%), and imazamox at 0.044 kg ai ha−1 (10%). These treatments also yielded the lowest aboveground biomass values. The results of this study demonstrate that M. sinensis is more tolerant of the POST herbicides tested here than M.×x. giganteus. Several herbicide options may be available for weed management in M. sinensis and M. × giganteus stands following additional field trials to validate initial findings. Nomenclature: Aminopyralid; dicamba; foramsulfuron; glyphosate; halosulfuron; imazamox; imazethapyr; nicosulfuron; rimsulfuron; Miscanthus sinensis; Miscanthus × giganteus.

The genetic and phenotypic variability of interspecific hybrid bermudagrasses (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) used on golf course putting greens

AbstractMain conclusionSome interspecific hybrid bermudagrass cultivars used on golf course putting greens are genetically unstable, which has caused phenotypically different off-type grasses to occur in production nurseries and putting surfaces. Management practices to reduce the occurrence of off-type grasses in putting green surfaces and the effect they can have on putting quality and performance need to be researched until genetically stable cultivars are developed. Golf course putting green surfaces in subtropical and tropical climates are typically planted with an interspecific hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy), because of the superior putting quality and performance of these cultivars. ‘Tifgreen’ was one of the first interspecific hybrids developed for putting green use in lieu of common bermudagrass. However, off-type grasses began appearing in established Tifgreen stands soon after commercial release. Off-type grasses are those with different morphology and performance when compared to the surrounding, desirable cultivar. Off-types have the potential to decrease surface uniformity, which negatively affects putting surface quality. However, several unique off-types from Tifgreen have been selected as commercial cultivars, the first being ‘Tifdwarf’; then ‘Floradwarf’, ‘MS-Supreme’, ‘Pee Dee-102’, and ‘TL-2’, identified later. The cultivars ‘Champion Dwarf’, ‘P-18’, ‘RJT’, and ‘Emerald Dwarf’ were subsequently selected as off-types in Tifdwarf. The naturally occurring off-types and cultivars that have been identified within the Tifgreen family have widely differing phenotypes; however, they are reported to be genetically similar, supporting the hypothesis that their occurrence is a result of somatic mutations. Genetic instability in currently available commercial cultivars is likely to lead to the continued presence of off-types in production nurseries and putting greens. Additional research is needed to understand the nature of genetic instability in Tifgreen-derived cultivars and how to manage its consequences to develop new cultivars, but also strategies for eradication of off-types in pedigree nursery production and end-site putting greens.

Spatiotemporal variation of site-specific management units on natural turfgrass sports fields during dry down

Site-specific management units (SSMUs) are fundamental for the implementation of Precision Turfgrass Management. Short-term spatiotemporal variations of soil compaction and turfgrass vigor may be dynamic during a dry down period on natural turfgrass sports fields. This is due to the inverse relationship between soil compaction and soil moisture/drought stress, which may impact SSMU delineation and identification of site-specific deficient areas within a field. The spatiotemporal change of soil moisture, soil compaction, and turfgrass vigor SSMUs [as measured by volumetric water content (VWC), penetration resistance, and normalized difference vegetative index (NDVI)] were evaluated three times during a dry down from rainfall on native soil and sand capped natural turfgrass sports fields. The relationship of penetration resistance and NDVI with VWC was strongest and only significant on the native soil field during the dry down period. In general, as the fields dried, the magnitude of VWC SSMUs and NDVI SSMUs decreased, while the magnitude of penetration resistance SSMUs increased. This phenomenon was more drastic on the native soil field. Significant changes in spatial distributions were observed for VWC SSMUs and penetration resistance SSMUs on the native soil field; however, minimal changes were reported on the sand capped field. The spatial distributions of NDVI SSMUs were minimal on both fields. It is concluded that short-term spatiotemporal variations of SSMUs on sports fields during a dry down can be significant and considerations should be made prior to sampling based on the objective.

Sulfentrazone and Carfentrazone Accelerate Broadleaf Weed Control with Metsulfuron

Abstract Ground ivy and khakiweed are troublesome broadleaf weeds of warm-season turfgrass. Field studies were conducted in Tennessee (TN) and Texas (TX) from 2008 to 2010 to evaluate the efficacy of sulfentrazone plus metsulfuron and carfentrazone plus metsulfuron tank mixtures compared with metsulfuron alone for control of ground ivy and khakiweed. In TN, sulfentrazone plus metsulfuron and carfentrazone plus metsulfuron provided accelerated control of ground ivy compared with metsulfuron alone. Over a 2-yr period, ground ivy control with metsulfuron at 10, 21, and 42 g ai ha−1 ranged from 0 to 5% 7 d after treatment (DAT) and 12 to 60% 14 DAT. Ground ivy control with mixtures of sulfentrazone plus metsulfuron ranged from 40 to 72% 7 DAT and 87 to 100% 14 DAT. Similarly, carfentrazone plus metsulfuron controlled ground ivy 5 to 32% 7 DAT and 23 to 93% 14 DAT. In TX, carfentrazone plus metsulfuron and sulfentrazone plus metsulfuron controlled khakiweed greater than metsulfuron alone 7 and 14 DAT as well. Few differences in ground ivy and khakiweed control were detected 56 DAT because metsulfuron applied alone at 21 g ai ha−1 controlled both weeds > 77%, similar to each mixture. These data indicate that when applied in mixtures, sulfentrazone and carfentrazone accelerate ground ivy and khakiweed control with metsulfuron but do not affect long-term efficacy. Nomenclature: Carfentrazone; metsulfuron; sulfentrazone; ground ivy, Glechoma hederacea L.; khakiweed; Alternanthera pungens Kunth.

Response of Glyphosate-Resistant and Glyphosate-Susceptible Bentgrass (Agrostis spp.) to Postemergence Herbicides1

Studies were conducted in the summer and fall of 2001 in North Brunswick, NJ, and Marion County, Oregon, to evaluate the response of glyphosate-resistant and glyphosate-susceptible creeping bentgrass hybrids, colonial bentgrass, redtop, and dryland bentgrass grown as individual plants to postemergence (POST) herbicides. Glyphosate at 1.7 kg ae/ha, glufosinate at 1.7 kg ai/ha, fluazifop-P at 0.3 and 0.4 kg ai/ha, clethodim at 0.3 kg ai/ha, sethoxydim at 0.5 kg ai/ha, and a combination of glyphosate and fluazifop-P were applied 6 wk after planting. Glyphosate provided almost complete control of all susceptible bentgrass species at 4 weeks after treatment (WAT). Glufosinate provided 95% or greater control of all bentgrass species at 4 WAT, but regrowth was observed on all species in the summer experiment in Oregon. Fluazifop-P, clethodim, and sethoxydim provided slower control of bentgrass species, which ranged from 38 to 94% at 4 WAT, depending on species, herbicide, and experimental location. By 8 WAT, fluazifop-P at 0.4 kg/ha applied alone or in combination with glyphosate showed the highest levels of control (>90%) across all bentgrass species. Studies were also conducted in 2002 in the spring and summer in North Carolina to evaluate the response of a mature stand of glyphosate-susceptible ‘Penncross’ creeping bentgrass to POST herbicides. Two applications of glyphosate at 1.7 kg/ha were required to achieve 98% bentgrass control at 8 WAT. Fluazifop-P at 0.4 kg/ha, clethodim at 0.3 kg/ha, and sethoxydim at 0.4 kg/ha exhibited herbicidal activity, but two applications were required to reach (>82%) control of bentgrass at 8 WAT. Two sequential applications of clethodim or the combination of glyphosate and fluazifop-P provided 98% control of bentgrass at 8 WAT. Of the other herbicide treatments evaluated, only atrazine and sulfosulfuron provided (>80%) control at 8 WAT. The results of these studies demonstrate that fluazifop-P, clethodim, and sethoxydim have substantial herbicide activity on bentgrass species and may be viable alternatives to glyphosate for control of glyphosate-resistant creeping bentgrass and related bentgrass species in areas where they are not wanted. Glufosinate, atrazine, and sulfosulfuron also exhibited substantial herbicidal activity on bentgrass, and further research with these herbicides is warranted. Nomenclature: Atrazine; clethodim; glufosinate; glyphosate; fluazifop-P; sethoxydim; sulfometuron; sulfosulfuron; colonial bentgrass, Agrostis tenuis Sibth. #3 AGSTE ‘SR 7100’; creeping bentgrass, Agrostis stolonifera L. # AGSST ‘Backspin’, ‘Crenshaw’, ‘Penn A-4’, ‘Penncross’, ‘RR368’, ‘RS368’; dryland bentgrass, Agrostis castellana Boiss. and Reut. # AGSCT ‘Trust’; redtop, Agrostis gigantea Roth # AGSGI ‘Streaker’. Additional index words: Glyphosate resistance, imazaquin, isoxaflutole, metribuzin, MSMA, rimsulfuron. Abbreviations: ACCase, acetyl-CoA carboxylase; EPSP, 5-enolpyruvylshikimate-3-phosphate synthase; WAT, weeks after treatment.

Does variability within natural turfgrass sports fields influence ground-derived injuries?

Abstract Natural turfgrass sports fields exhibit within-field variations due to climatic conditions, field construction, field management, and foot traffic patterns from field usage. Variations within a field could influence the playing surface predictability and require athletes to make abrupt or frequent adjustments that lead to increased ground-derived injury occurrence. This study introduces a new methodology aimed at evaluating the potential relationship between within-field variations of turfgrass sports field properties and ground-derived athlete injuries. Collegiate Club Sport athletes self-reported ground-derived injuries over two years. Soil moisture, turfgrass quality, surface hardness, and turfgrass shear strength were quantified from their two home fields. Hot spot analysis identified significantly high (hot spots) and low (cold spots) values within the fields. Injury locations were compared to hot spot maps each month. Binomial proportion tests determined if there were differences between observed injury proportions and expected proportions. Twenty-three ground-derived injuries were reported overall. The observed injury proportions occurring in turfgrass quality cold spots [0.52 (95% CI 0.29–0.76)] and soil moisture hot spots [0.43 (95% CI 0.22–0.66)] was significantly higher than expected [0.20 (p < .001) and 0.21 (p < .05), respectively]. Most injuries in significant areas of turfgrass quality, soil moisture, and surface hardness were along edges of hot and cold spots. These results suggest a potential relationship between within-field variations and ground-derived injuries, particularly in transition areas between non-significant and significant high and low values. Future larger-scale studies can incorporate the reported methodology to validate this relationship and implement strategies that reduce ground-derived injuries.

Tolerance of Hooker's Evening Primrose (Oenothera elata) Transplants to Postemergence Herbicides

Abstract Greenhouse trials were conducted to determine Hookers evening primrose transplant tolerance to POST-applied herbicides. Herbicide treatments consisted of glyphosate at 1.68 kg ae ha−1, glufosinate at 0.84 kg ai ha−1, fenoxaprop at 0.10 kg ai ha−1, fluazifop at 0.45 kg ai ha−1 + a nonionic surfactant (NIS) at 0.25% v/v, sulfosulfuron at 0.06 kg ai ha−1 + NIS at 0.25% v/v, quinclorac at 0.42 kg ae ha−1 + methylated seed oil (MSO) at 0.5% v/v, mesotrione at 0.21 kg ai ha−1, and the combination of quinclorac + mecoprop + dicamba at 0.42 + 0.21 + 0.06 kg ae ha−1 + MSO at 0.5% v/v. Fluazifop (14%) and fenoxaprop (19%) treatments did not result in any significant phytotoxicity 7 d after treatment (DAT) compared with the nontreated check. Hookers evening primrose exhibited 26 to 37% phytotoxicity in response to quinclorac, glyphosate, or sulfosulfuron 7 DAT. Phytotoxicity ≥ 50% was observed for mesotrione, glufosinate, and the combination of quinclorac + mecoprop + dicamba 7 DAT. Phytotoxicity increased for all treatments 28 DAT. Fluazifop (21%) was the only treatment that did not exhibit phytotoxicity symptoms different from the nontreated check 28 DAT. Hookers evening primrose exhibited 31 to 40% phytotoxicity with applications of fenoxaprop, glyphosate, or glufosinate 28 DAT. Phytotoxicity was ≥ 58% with all other treatments 28 DAT. Fluazifop exhibited similar above-ground (12.4 g) and below-ground (16.4 g) biomass as the nontreated check (10.8 and 14.7 g, respectively) 28 DAT. All other treatments resulted in 1.6 to 5 g of above-ground biomass and 0.8 to 4.3 g of below-ground biomass 28 DAT. Fluazifop (24.3) and fenoxaprop (18.8) applications resulted in a plant growth index (PGI) that was not significantly different from the nontreated check (24.7) 28 DAT. A PGI ≤ 16.2 was observed for all other treatments 28 DAT. Nomenclature: Dicamba; fenoxaprop; fluazifop; glufosinate; glyphosate; mecoprop; mesotrione; quinclorac; sulfosulfuron; Hookers evening primrose, Oenothera elata Kunth OEEL Resumen Experimentos de invernadero fueron realizados para determinar la tolerancia de trasplantes de Oenothera elata a herbicidas aplicados POST. Los tratamientos de herbicidas fueron glyphosate a 1.68 kg ae ha−1, glufosinate a 0.84 kg ai ha−1, fenoxaprop a 0.10 kg ai ha−1, fluazifop a 0.45 kg ai ha−1 + surfactante no-iónico (NIS) a 0.25% v/v, sulfosulfuron a 0.06 kg ai ha−1 + NIS a 0.25% v/v, quinclorac a 0.42 kg ae ha−1 + aceite de semilla metilado (MSO) a 0.5% v/v, mesotrione a 0.21 kg ai ha−1, y la combinación de quinclorac + mecoprop + dicamba a 0.42 + 0.21 + 0.06 kg ae ha−1 + MSO a 0.5% v/v. Los tratamientos de fluazifop (14%) y fenoxaprop (19%) no resultaron en fitotoxicidad significativa 7 d después del tratamiento (DAT) en comparación con los testigos no tratados. O. elata mostró 26 a 37% de fitotoxicidad en respuesta a quinclorac, glyphosate, o sulfosulfuron 7 DAT. Fitotoxicidad ≥50% se observó con mesotrione, glufosinate, y la combinación de quinclorac + mecoprop + dicamba 7 DAT. La fitotoxicidad incrementó para todos los tratamientos 28 DAT. Fluazifop (21%) fue el único tratamiento que no mostró síntomas de fitotoxicidad diferentes al testigo no tratado 28 DAT. O. elata mostró 31 a 40% de fitotoxicidad con aplicaciones de fenoxaprop, glyphosate, o glufosinate 28 DAT. La fitotoxicidad fue ≥58% con todos los demás tratamientos 28 DAT. Fluazifop mostró biomasa aérea (12.4 g) y subterránea (16.4 g) similares al testigo no tratado (10.8 y 14.6 g, respectivamente) 28 DAT. Todos los demás tratamientos resultaron en 1.6 a 5 g de biomasa aérea y 0.8 a 4.3 g de biomasa subterránea 28 DAT. Las aplicaciones de fluazifop (24.3) y fenoxaprop (18.8) resultaron en un índice de crecimiento vegetal (PGI) que no fue significativamente diferente al testigo no tratado (24.7) 28 DAT. Un PGI ≤16.2 se observó en todos los demás tratamientos 28 DAT.

Purple Nutsedge (Cyperus rotundus) Control in Bermudagrass Turf with Imazosulfuron

Abstract Purple nutsedge response to various rates and timings of imazosulfuron was evaluated in 2007 and 2008 in Abilene, TX. Bermudagrass phytotoxicity never exceeded 4% throughout the duration of the trial and all bermudagrass recovered within 7 d of herbicide application. Imazosulfuron (0.56 kg ai ha−1) followed by (fb) imazosulfuron 1 wk after initial treatment (WAIT), imazosulfuron at 1.12 kg ai ha−1, and trifloxysulfuron at 0.03 kg ai ha−1 exhibited 94 to 96% control 4 WAIT. Imazosulfuron (0.56 kg ai ha−1) fb imazosulfuron 2, 3, and 4 WAIT exhibited 99% control 4 WAIT. Eight weeks later (12 WAIT), imazosulfuron (0.56 kg ai ha−1) fb imazosulfuron 3 WAIT controlled purple nutsedge 91%, whereas similar control (82 to 84%) was observed with a single application of trifloxysulfuron and imazosulfuron (0.56 kg ai ha−1) fb imazosulfuron 2 and 4 WAIT. A single application of imazosulfuron at 1.12 kg ai ha−1 and sequential treatment with imazosulfuron (0.56 kg ai ha−1) on a 1-wk interval only controlled purple nutsedge 51 to 69% 12 WAIT. Timing of sequential imazosulfuron application was identified as an important component of the purple nutsedge control program. Waiting 2, 3, or 4 WAIT for sequential imazosulfuron applications, rather than 1 WAIT, increased purple nutsedge control 31 to 40% 12 WAIT. The highest level of purple nutsedge control (91%) was observed with applications of imazosulfuron (0.56 kg ai ha−1) fb imazosulfuron 3 WAIT applied during midsummer. However, control with this treatment was statistically similar to control with a single application of trifloxysulfuron (82%). Nomenclature: Imazosulfuron (2-chloro-N-[[4,6-dimethoxy-2-pyrimidinyl-amino]carbonyl]imidazo[1,2-a]pyridine-3-sulfonamide); trifloxysulfuron; common bermudagrass, Cynodon dactylon (L.) Pers. CYNDA; purple nutsedge, Cyperus rotundus L. CYPRO.