S. Christopher Marble

Early Postemergence Control of Yellow Woodsorrel (Oxalis stricta) with Residual Herbicides

Abstract Three experiments were conducted to evaluate early POST control of yellow woodsorrel using PRE-applied herbicides. In experiment 1, yellow woodsorrel was seeded at two dates in a commercial pine-bark substrate and grown until reaching either the cotyledon–one-leaf (C-1L) or two- to four-leaf (2-4L) growth stage. The herbicides isoxaben, indaziflam, and dimethenamid-p were applied at these growth stages. Two rates of isoxaben and indaziflam provided yellow woodsorrel control (≥ 80% reduction in fresh weight [FW]) when applied at the C-1L stage; however, once yellow woodsorrel reached the 2-4L stage, indaziflam was the only herbicide that provided effective control at both rates tested. Experiments 2 and 3 were similar to experiment 1, except two labeled rates of dithiopyr were also evaluated. In experiment 2, all herbicides evaluated provided ≥ 90% reduction in FW of yellow woodsorrel at the C-1L stage. Although no differences in FW were observed among any of the herbicide treatments when yellow woodsorrel were treated at the 2-4L stage, control ratings indicated that indaziflam provided the most effective yellow woodsorrel control. Experiment 3 results also indicated that isoxaben, indaziflam, and dithiopyr controlled yellow woodsorrel (≥ 95% reduction in FW) when treatments were applied at the C-1L stage, whereas dimethenamid-p reduced shoot FW 70%. When yellow woodsorrel was treated after reaching the 2-4L stage, indaziflam provided the greatest control of any herbicide evaluated. Nomenclature: Dithiopyr; isoxaben; indaziflam, N-[(1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1-yl]-6-[(1RS)-1-fluoroethyl]-1,3,5-triazine-2,4-diamine); yellow woodsorrel, Oxalis stricta L. Resumen Se realizaron tres experimentos para evaluar el control POST temprano de Oxalis stricta usando herbicidas aplicados PRE. En el experimento 1, O. stricta se sembró en dos fechas en un sustrato comercial de corteza de pino y se dejó crecer hasta alcanzar los estados de desarrollo de cotiledón-una hoja (C-1L) o dos a cuatro hojas (2-4L). Los herbicidas isoxaben, indaziflam, y dimethenamid-p fueron aplicados en estos estados de desarrollo. Ambas dosis de isoxaben e indaziflam proveyeron control de O. stricta (≥80% reducción del peso fresco [FW] cuando se aplicó en el estado C-1L); sin embargo, una vez que O. stricta alcanzó el estado 2-4L, indaziflam fue el único herbicida que brindó control efectivo con ambas de las dosis evaluadas. Los experimentos 2 y 3 fueron similares al experimento 1, excepto que dos dosis de etiqueta de dithiopyr fueron también evaluadas. En el experimento 2, todo los herbicidas evaluados causaron ≥90% reducción de FW de O. stricta en el estado C-1L. Aunque no se observaron diferencias en FW entre ninguno de los tratamientos de herbicidas cuando O. stricta se trató en el estado 2-4L, las evaluaciones de control indicaron que indaziflam brindó el control más efectivo de esta maleza. Los resultados del experimento 3 indicaron que isoxaben, indaziflam, y dithiopyr controlaron O. stricta (≥95% reducción de FW) cuando los tratamientos fueron aplicados en el estado C-1L, mientras dimethenamid-p redujo el FW de la parte aérea 70%. Cuando O. stricta se trató después de alcanzar el estado 2-4L, indaziflam brindó el mayor control entre los herbicidas evaluados.

Herbicide and Mulch Interactions: A Review of the Literature and Implications for the Landscape Maintenance Industry

Abstract Use of organic mulch is one of the most common methods of weed control in landscape planting beds and provides other benefits, including improved soil characteristics, increased growth of ornamental plants, and enhanced property aesthetics. In the landscape maintenance industry, it is common to apply mulch and herbicides concurrently to landscape beds to provide long-term, broad-spectrum weed control. It is known that herbicides behave differently when applied to different soil types and organic materials; however, research is lacking concerning which herbicides are most effective with different mulch materials in the landscape. Determining the most effective herbicide–mulch combinations could potentially improve weed control, reduce labor costs from hand weeding, and mitigate negative environmental impacts resulting from off-site herbicide movement. The objective of this paper is to review the research that has been conducted pertaining to various mulch–herbicide combinations in the landscape and in other areas of agricultural production while also identifying key knowledge gaps that should be addressed in future research. Review of the literature suggests satisfactory weed control can be achieved with high mulch depths (≥ 7 cm) regardless of herbicide use, and herbicide–mulch interactions become more pronounced as mulch depth decreases. Additionally, future research is needed to determine which herbicides are best suited for different mulch types to improve weed control and potentially reduce environmental impacts, including herbicide leaching and runoff into urban and suburban waterbodies. Resumen El uso de coberturas orgánicas es uno de los métodos más comunes para el control de malezas en camas de siembra en paisajismo y brinda otros beneficios incluyendo el mejoramiento de las características del suelo, el aumento del crecimiento de plantas ornamentales, y mejores propiedades estéticas. En la industria de mantenimiento de paisajes, es común aplicar coberturas y herbicidas concurrentemente a camas de siembra para brindar un control de malezas más duradero y de amplio espectro. Es sabido que los herbicidas se comportan de forma diferente cuando se aplican a diferentes tipos de suelos y materiales orgánicos. Sin embargo, hay un faltante de información acerca de cuáles herbicidas son más efectivos dependiendo de los materiales para cobertura para paisajes. El determinar la combinación herbicida-cobertura más efectiva podría potencialmente mejorar el control de malezas, reducir los costos de deshierba manual, y mitigar los impactos negativos en el ambiente producto del movimiento no deseado de herbicidas. El objetivo de este artículo es revisar la investigación que se ha realizado relacionada a varias combinaciones cobertura-herbicida en paisajes y en otras áreas de producción agrícola, y a la vez identificar faltantes clave en información que podrían ser el tema de investigaciones futuras. La revisión de literatura sugiere que el control satisfactorio de malezas puede ser alcanzado con coberturas profundas (≥ 7 cm) sin importar el uso de herbicidas, y que las interacciones herbicida-cobertura se vuelven más pronunciadas a medida que la profundidad de la cobertura disminuye. Adicionalmente, se necesitan investigaciones para determinar cuáles herbicidas son los más adecuados para diferentes tipos de coberturas, para así mejorar el control de malezas y potencialmente reducir impactos ambientales, los cuales incluyen lixiviación y escorrentía de herbicidas a cuerpos de agua en zonas urbanas y suburbanas.

Impact of Application Rate, Timing, and Indaziflam Formulation on Early Postemergence Control of Oxalis stricta

Although primarily used as an effective PRE herbicide, indaziflam has been shown to provide early POST control of some weeds commonly found in nursery production. Previous investigation on the early POST efficacy of indaziflam focused on the liquid formulation, and the ability of the granular formulation to provide early POST weed control is unknown. Nursery trials were conducted to evaluate early POST control of oxalis using two formulations of indaziflam. Oxalis seeds were surface sown to nursery containers at two separate dates and grown until they reached the two- to four-leaf stage (2-4L) and six- to eight-leaf stage. Both growth stages were treated with indaziflam at 12.6, 25.1, 50.2, and 100.4 g ai ha−1 using either a granular (G) or liquid (SC) formulation. A chemical control treatment (glyphosate) and a nontreated control were also included for comparison. The SC formulation provided > 90% control of both oxalis growth stages at all four rates and was similar to glyphosate. The G formulation at 12.6 and 25.1 g ha−1 only provided marginal control, but overall performed similarly to the SC formulation at the 50.2 and 100.4 g ha−1 rate in most experiments. In contrast to the SC formulation, the G formulation is labeled for use over the top of container-grown nursery crops. Results of this research indicate that in areas where oxalis is the primary weed of concern, the G formulation of indaziflam could be applied to control small oxalis up to the 2-4L stage at the currently labeled rate (50.2 g ha−1). Nomenclature: Indaziflam; glyphosate; Oxalis stricta L. Aunque se usa principalmente como un herbicida PRE efectivo, indaziflam ha mostrado poder brindar control POST temprano de varias especies de malezas comúnmente encontradas en la producción de almácigas en viveros. Investigación previa sobre la eficacia de indaziflam en POST temprano se enfocó en la formulación líquida, pero se desconoce la habilidad de la formulación granular de brindar control POST temprano de malezas. Se realizaron experimentos en vivero para evaluar el control POST temprano de Oxalis usando dos formulaciones de indaziflam. Semillas de Oxalis fueron sembradas en la superficie de contenedores en dos fechas separadas y las plantas fueron crecidas hasta alcanzar los estadios de dos a cuatro hojas (2-4L) y seis a ocho hojas. Ambos estadios de crecimiento fueron tratados con indaziflam a 12.6, 25.1, 50.2, y 100.4 g ai ha−1 usando, ya fuese la formulación granular (G) o líquida (SC). También se incluyó un tratamiento testigo químico (glyphosate) y un testigo sin tratamiento para fines de comparación. La formulación SC brindó >90% de control de Oxalis en ambos estadios de crecimiento con las cuatro dosis y este control fue similar al de glyphosate. La formulación G a 12.6 y 25.1 g ha−1 solamente brindó un control marginal, pero su desempeño general fue similar a la formulación SC a dosis de 50.2 y 100.4 g ha−1 en la mayoría de los experimentos. En contraste con la formulación SC, la formulación G está registrada para uso en cultivos de vivero aplicada sobre plantas crecidas en contenedores. Los resultados de esta investigación indican que en áreas donde Oxalis es la principal maleza, la formulación G de indaziflam podría ser aplicada para el control de plantas de Oxalis pequeñas hasta el estadio de 2-4 L a la dosis de etiqueta actual (50.2 g ha−1).

Preemergence and Postemergence Control of Artilleryweed (Pilea microphylla) in Container Nurseries and Landscapes

Artilleryweed is an annual or short-lived perennial weed that is becoming increasingly problematic in nurseries and landscapes in tropical and subtropical environments. Currently, no herbicide recommendations exist for management of artilleryweed. Objectives of this trial were to evaluate PRE and POST herbicides for efficacy on artilleryweed. All studies were conducted in Apopka, FL in a shaded greenhouse. Herbicides evaluated for POST control included diquat, dimethenamid-P, flumioxazin, glufosinate, glyphosate, indaziflam, oxadiazon, pelargonic acid, sulfentrazone and sulfosulfuron applied at their highest labelled rates to mature (10 to 12 cm height) artilleryweed. For PRE experiments, pots were overseeded with artilleryweed seed and treated with dimethenamid-P, indaziflam, isoxaben, oxadiazon, oxyfluorfen + prodiamine, oxyfluorfen + pendimethalin, pendimethalin, pendimethalin + dimethenamid-P, prodiamine, prodiamine + isoxaben, S-metolachlor, or trifluralin + isoxaben. When assessing both initial fresh weight and regrowth, flumioxazin and glufosinate provided the most consistent POST control when applied at the highest labelled rate, although regrowth did occur following application with glufosinate. All PRE herbicides evaluated provided over 90% control of artilleryweed with the exception of isoxaben and trifluralin + isoxaben. Results indicate that several effective options exist for artilleryweed management, but more effective control will likely be achieved when herbicides are applied PRE. Nomenclature: Dimethenamid-P; diquat; flumioxazin; glufosinate; glyphosate; indaziflam; isoxaben; oxadiazon; oxyfluorfen; pelargonic acid; pendimethalin; prodiamine; S-metolachlor; sulfentrazone; sulfosulfuron; trifluralin; artilleryweed, Pilea microphylla (L.) Liebm.

Species and Media Effects on Soil Carbon Dynamics in the Landscape.

Three woody shrub species [cleyera (Ternstroemia gymnanthera Thunb. ‘Conthery’), Indian hawthorn (Rhaphiolepis indica L.) and loropetalum (Loropetalum chinensis Oliv.‘Ruby’)] were container-grown for one growing season in 2008 using either pinebark (industry standard), clean chip residual or WholeTree (derived by-products from the forestry industry) as potting substrates and then transplanted into the landscape in 2008. An Automated Carbon Efflux System was used to continually monitor soil CO2 efflux from December 2010 through November 2011 in each species and substrate combination. Changes in soil carbon (C) levels as a result of potting substrate were assessed through soil sampling in 2009 and 2011 and plant biomass was determined at study conclusion. Results showed that soil CO2-C efflux was similar among all species and substrates, with few main effects of species or substrate observed throughout the study. Soil analysis showed that plots with pinebark contained higher levels of soil C in both 2009 and 2011, suggesting that pinebark decomposes slower than clean chip residual or WholeTree and consequently has greater C storage potential than the two alternative substrates. Results showed a net C gain for all species and substrate combinations; however, plants grown in pinebark had greater C sequestration potential.