Peter J. Dittmar

Effect of PRE and POST-Directed Herbicides for Season-Long Nutsedge (Cyperus spp.) Control in Bell Pepper

Abstract Fomesafen and imazosulfuron are two recently registered herbicides for use in Florida bell pepper. Field studies were conducted in 2012 and 2013 to evaluate PRE, POST-directed (POST-DIR), and PRE followed by (fb) POST-DIR control programs utilizing these new herbicides for nutsedge control in Florida bell pepper. PRE treatments included: S-metolachlor at 0.71 and 1.07 kg ai ha−1, fomesafen at 0.28 and 0.42 kg ai ha−1, S-metolachlor at 0.71 kg ha−1 + fomesafen 0.28 kg ha−1, and S-metolachlor at 1.07 kg ha−1 + fomesafen at 0.42 kg ha−1. POST-DIR treatments included imazosulfuron at 0.21 and 0.34 kg ai ha−1. PRE fb POST-DIR treatments included S-metolachlor at 0.71 or 1.07 kg ha−1 fb imazosulfuron at 0.21 kg ha−1 and fomesafen at 0.28 or 0.42 kg ha−1 fb imazosulfuron at 0.21 kg ha−1. Nutsedge control in both years at 28 d after planting was similar among all PRE treatments providing ≤ 60% control. The addition of imazosulfuron POST-DIR following S-metolachlor or fomesafen PRE provided greater control compared to S-metolachlor or fomesafen alone 14, 21, and 28 d after the POST-DIR application. Plots treated with S-metolachlor resulted in lower marketable weight and marketable fruit count compared to fomesafen in 2012; however, this was not observed in 2013. The results for these studies indicate the importance of a PRE fb POST-DIR herbicide for nutsedge control and that fomesafen or S-metolachlor PRE fb imazosulfuron POST-DIR provides growers with a viable tool capable of achieving season-long control of nutsedge in bell pepper. Nomenclature: Fomesafen; imazosulfuron; S-metolachlor; nutsedge, Cyperus spp.; bell pepper, Capsicum annuum L. Resumen Fomesafen e imazosulfuron son dos herbicidas recientemente registrados para uso en pimentón en Florida. Se realizaron estudios de campo en 2012 y 2013 para evaluar programas de control PRE, POST-dirigido (POST-DIR), y PRE seguido por (fb) POST-DIR utilizando estos nuevos herbicidas para el control de Cyperus spp. en pimentón en Florida. Los tratamientos PRE incluyeron: S-metolachlor a 0.71 y 1.07 kg ai ha−1, fomesafen a 0.28 y 0.42 kg ai ha−1, S-metolachlor a 0.71 kg ha−1 + fomesafen 0.28 kg ha−1, y S-metolachlor a 1.07 kg ha−1 + fomesafen 0.42 kg ha−1. Los tratamientos POST-DIR incluyeron imazosulfuron a 0.21 y 0.34 kg ai ha−1. Los tratamientos PRE fb POST-DIR incluyeron S-metolachlor a 0.71 ó 1.07 kg ha−1 fb imazosulfuron a 0.21 kg ha−1, y fomesafen a 0.28 ó 0.42 kg ha−1 fb imazosulfuron a 0.21 kg ha−1. El control de Cyperus spp. en ambos años a 28 d después de la siembra fue similar entre todos los tratamientos PRE siendo ≤ 60% de control. El agregar imazosulfuron POST-DIR después de S-metolachlor o de fomesafen PRE brindó mayor control al compararse con S-metolachlor o fomesafen solos 14, 21, y 28 d después de la aplicación POST-DIR. Los lotes tratados con S-metolachlor resultaron en menor peso y número de fruto comercializable al compararse con fomesafen en 2012, sin embargo esto no se observó en 2013. Los resultados de estos estudios indican la importancia de herbicidas PRE fb POST-DIR para el control de Cyperus spp. y que fomesafen o S-metolachlor PRE fb imazosulfuron POST-DIR brindan a los productores una herramienta viable capaz de alcanzar control de Cyperus spp. a lo largo de toda la temporada de crecimiento del pimentón.

Effect of Drip-Applied Herbicides on Yellow Nutsedge (Cyperus esculentus) in Plasticulture

Abstract Greenhouse and field studies were conducted to determine the effect of halosulfuron, imazosulfuron, and trifloxysulfuron applied through drip irrigation on yellow nutsedge. In greenhouse studies, yellow nutsedge control by halosulfuron, imazosulfuron, and trifloxysulfuron was greater (69 to 91%) than the nontreated control (0%). Yellow nutsedge treated with halosulfuron POST had a lower photosynthetic rate (0.6 to 22.6 µmol m−2 s−1) at 4, 7, and 14 d after treatment than the nontreated control (3.3 to 26.2 µmol m−2 s−1). Yellow nutsedge treated with trifloxysulfuron had lower photosynthetic rate and stomatal conductance than the nontreated plants. In field studies at Clinton, NC, yellow nutsedge density increased from treatment (day 0) to 56 d after treatment in all treatments. Increase in yellow nutsedge density was 72 and 95% in drip-applied halosulfuron and imazosulfuron treatments compared with yellow nutsedge density increases of 876% for the same period in the nontreated plots. Yellow nutsedge density increased 69 and 57% at Clinton and Kinston, NC, respectively, in the drip-applied 15 g ha−1 trifloxysulfuron treatment compared with 876% in the nontreated control. In field studies at Clinton and Kinston, NC, suppression of yellow nutsedge emergence in POST and drip-applied herbicide treatments was similar. Emergence of yellow nutsedge was similar in the imazosulfuron POST and the nontreated yellow nutsedge. Based on these studies, drip-applied herbicides may be beneficial as a part of a yellow nutsedge control program, but additional measures, such as a POST herbicide, would be needed for effective control. Drip-applied herbicides may give growers an option for herbicide application after drip irrigation tape and polyethylene mulch have been installed in the current vegetable crops. This application method would also allow herbicide treatment under plastic mulch used for multicropping systems. Nomenclature: Halosulfuron; imazosulfuron; trifloxysulfuron; yellow nutsedge, Cyperus esculentus L.

Tolerance of Tomato to Herbicides Applied through Drip Irrigation

Abstract Greenhouse and field studies were conducted to determine tolerance of tomato to halosulfuron, imazosulfuron, and trifloxysulfuron herbicides applied through drip irrigation. In greenhouse studies, PRE- and POST-applied trifloxysulfuron caused greater tomato injury (14 and 54% injury, respectively) than PRE- and POST-applied halosulfuron (5 and 26% injury, respectively) or imazosulfuron (5 and 23% injury, respectively). All herbicide treatments in the greenhouse studies caused greater injury to tomato than the nontreated. Greater tomato injury was observed in the greenhouse from herbicides applied POST than when soil applied. Tomato injury from POST-applied halosulfuron, imazosulfuron, or trifloxysulfuron followed a linear relationship, with tomato injury increasing with increasing herbicide rate. Tomato photosynthetic rate did not differ among the herbicide treatments (32.7 to 55.0 μmol m−2 s−1) and the nontreated (38.0 to 55.0 μmol m−2 s−1). At 5 to 16 days after treatment (DAT), tomato treated with imazosulfuron POST (0.26 to 0.46 cm s−1) or trifloxysulfuron POST (0.27 to 0.51 cm s−1) had lower stomatal conductance compared to the stomatal conductance of the nontreated tomato (0.65 to 0.76 cm s−1). Chlorophyll content did not differ among treatments at 0 to 6 DAT. At 7 to 12 DAT, tomato treated with imazosulfuron POST (34.0 to 40.1 SPAD) and trifloxysulfuron POST (35.0 to 41.6 SPAD) had lower chlorophyll content compared to the nontreated (39.1 to 48.1 SPAD). In 2008 and 2009 field studies, no tomato injury was observed. Herbicide, herbicide application method, and herbicide rate had no effect on tomato height (73 to 77 cm 14 DAT, 79 to 84 cm 21 DAT) and total fruit yield (62,722 to 80,328 kg ha−1). Nomenclature: Halosulfuron; imazosulfuron; trifloxysulfuron; tomato; Solanum lycopersicum L. Resumen Se realizaron estudios de invernadero y de campo para determinar la tolerancia del tomate a halosulfuron, imazosulfuron y trifloxysulfuron aplicados a travõs de un sistema de riego por goteo. En los estudios de invernadero, trifloxysulfuron aplicado PRE y POST causõ más dańo al tomate (14 y 54%, respectivamente) que halosulfuron aplicado PRE y POST (5 y 26%, respectivamente) o imazosulfuron (5 y 23%, respectivamente). En los estudios de invernadero, todos los tratamientos de herbicidas causaron mayor daño al tomate que el testigo no-tratado. En el invernadero cuando se aplicaron los herbicidas POST, se observõ un mayor daño que cuando se aplicaron al suelo. El daño al tomate causado por halosulfuron, imazosulfuron o trifloxysulfuron aplicados POST siguiõ una relaciõn lineal, incrementándose el daño al tomate conforme incrementõ la dosis del herbicida. La tasa fotosintõtica del tomate no difiriõ entre los tratamientos de herbicidas (32.7 a 55.0 mol m-2 s-1) y el testigo no-tratado (38.0 a 55.0 mol m-2 s-1). De 5 a 16 dúas despuõs del tratamiento (DAT), el tomate tratado con imazosulfuron POST (0.26 a 0.46 cm s-1) o trifloxysulfuron (0.27 a 0.52 cm s-1) tuvo una menor conductancia estomática comparado con el tomate no-tratado (0.65 a 0.76 cm s-1). El contenido de clorofila no difiriõ entre tratamientos de 0 a 6 DAT. De 7 a 12 DAT, el tomate tratado con imazosulfuron POST (34.0 a 40.1 SPAD) and trifloxysulfuron (35.0 a 41.6 SPAD) tuvo un menor contenido de clorofila comparado con el testigo no-tratado (39.1 a 48.1 SPAD). En los estudios de campo en 2008 y 2009, no se observõ ningún daño al tomate. El herbicida, el mõtodo de aplicaciõn del herbicida y la dosis del herbicida no tuvieron efecto sobre la altura del tomate (73 a 77 cm 14 DAT, 79 a 84 cm 21 DAT) y el rendimiento total de fruto (62,722 a 80,328 kg ha-1).

Clopyralid Dose Response for Two Black Medic (Medicago lupulina) Growth Stages

Black medic is a troublesome weed in commercial strawberry fields in Florida. It emerges during crop establishment from the planting holes punched in plastic mulches that are installed on raised beds. Clopyralid is registered for posttransplant applications at 140 to 280 g ae ha−1 but growers typically report suppression, not control. An outdoor potted experiment was designed to model the black medic dose-response curve and determine the effect of plant size at application on control. Two plant sizes were selected: designated small (0.5- to 1-cm stem length) and large (3- to 6-cm stem length). Dose-response curves were generated using a log-logistic four-parameter model. At 22 d after treatment (DAT), there was a significant interaction between clopyralid rate and black medic growth stage on both epinasty (P = 0.0022) and chlorosis (P = 0.0055). The effective dosage to induce 90% (ED90) epinasty were 249.5 and 398.3 g ha−1 for the small and large growth stages, respectively. The ED90 for chlorosis was 748.2 for the small growth stage, whereas the estimated value for the large was outside the measured range. For necrosis there was no significant effect of growth stage, and the ED90 was 1,856.3 g ha−1. The aboveground dry biomass ED90 for the small growth stage was 197.3 g ha−1, and the estimated ED90 value for the large was not within the measured range. Results indicate that clopyralid adequately controls black medic when applied at maximum label rates when stems were 0.5 to 1 cm long but not when plants were larger. Poor efficacy typically observed in commercial fields is likely due to black medic plant size or lack of herbicide coverage via shielding by strawberry plants. Nomenclature: Clopyralid; black medic, Medicago lupulina L. MEDLU. Medicago lupulina es una maleza problemática en campos comerciales de fresa en Florida. Esta maleza emerge durante el establecimiento del cultivo en los huecos hechos para el cultivo en la cobertura plástica sobre las camas de siembra. Clopyralid esta registrado para aplicaciones pos-trasplante a 140 a 280 g ae ha−1, pero los productores típicamente reportan supresión y no control de esta maleza. Se diseñó un experimento al aire libre en potes para modelar la curva de respuesta a dosis de M. lupulina, estimar la dosis de clopyralid requerida para alcanzar 90% de control, y determinar el efecto sobre el control del tamaño de planta al momento de la aplicación. Se seleccionaron dos tamaños de planta designados: pequeño (0.5 a 1 cm de longitud del tallo) y grande (3 a 6 cm de longitud del tallo). Las curvas de respuesta a dosis fueron generadas usando un modelo log-logístico de cuatro parámetros. A 22 d después del tratamiento (DAT), hubo una interacción significativa entre la dosis de clopyralid y el estadio de crecimiento de M. lupulina con respecto a epinastia (P = 0.0022) y clorosis (P = 0.0055). La dosis efectiva para inducir 90% (ED90) de epinastia fue 249.5 y 398.3 g ha−1 para los estadios pequeño y grande, respectivamente. La ED90 para clorosis fue 748.2 para el estadio pequeño, mientras que el valor estimado para el grande estuvo fuera del rango estudiado. Para necrosis, no hubo un efecto significativo del estadio de crecimiento, y la ED90 fue 1,856.3 g ha−1. La ED90 para biomasa aérea seca para el estadio pequeño fue 197.3 g ha−1, y el valor estimado de ED90 para el estadio grande no estuvo dentro del rango medido. Los resultados indican que clopyralid controla adecuadamente M. lupulina cuando se aplica a las dosis máximas de la etiqueta a tallos de 0.5 a 1 cm de longitud, pero no cuando las plantas son más grandes. La pobre eficacia típicamente observada en campos comerciales se debe probablemente al tamaño de planta de M lupulina o a una cobertura del herbicida limitada producto de la interferencia de las plantas de fresa.

Effects of Postemergence and Postemergence-Directed Halosulfuron on Triploid Watermelon (Citrullus Lanatus)

Studies were conducted in 2006 at Clinton and Kinston, NC, to determine the influence of halosulfuron POST (over the crop plant) or POST-directed (to the crop) on growth and yield of transplanted ‘Precious Petite’ and ‘Tri-X-313’ triploid watermelon. Treatments included a nontreated control, 39 g/ha halosulfuron applied POST-directed to 25% of the plant (distal or proximal region), POST-directed to 50% of the plant (distal or proximal; Precious Petite only), and POST. Watermelon treated with halosulfuron displayed chlorotic leaves, shortened internodes, and increased stem splitting. Vines were longest in the nontreated control (Tri-X-313  =  146 cm, Precious Petite  =  206 cm) but were shortest in the POST treatment (Tri-X-313  =  88 cm, Precious Petite  =  77 cm). Halosulfuron POST to watermelon caused the greatest injury (Tri-X-313  =  64%, Precious Petite  =  67%). Halosulfuron directed to 25 or 50% (distal or proximal) of the plant caused less injury than halosulfuron applied POST. Stem splitting was greatest when halosulfuron was applied to the proximal area of the stem compared with POST-directed distal or POST. Internode shortening was greatest in treatments where halosulfuron was applied to the distal region of the stem. However, Tri-X-313 in the POST-directed 25% distal treatment produced similar total and marketable fruit weight as the nontreated control at Clinton. Fruit number did not differ among treatments for either cultivar. At Kinston, Precious Petite nontreated control and POST-directed 25% distal end treatment had greater marketable fruit weight than the POST-directed 50% proximal and POST treatments. The current halosulfuron registration allows POST application between rows or PRE. Limiting halosulfuron contact to no more than 25% of the watermelon plant will likely improve crop tolerance. Nomenclature: Halosulfuron; watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai ‘Tri-X-313’ and ‘Precious Petite’

Impact of Application Time and Clopyralid Rate on Strawberry Growth and Yield

Hard-seeded, broadleaf, winter annual weeds in strawberry plasticulture production in Florida emerge in the crop holes in the plastic mulch and reduce berry yield and quality. Clopyralid is registered for POST control of broadleaf weeds, but herbicide damage has been observed in commercial fields, and preliminary observations suggest that effects vary with time of application. To address this issue, an experiment was conducted in 2012 to 2013 and 2013 to 2014 to evaluate clopyralid rate (0, 140, 280, and 560 g ae ha−1) and application time on strawberry vegetative and reproductive growth. Clopyralid applications at 280 and 560 g ae ha−1 on January 2 and 16, 2013 (yr 1) reduced leaf number per plant by 33 to 44% and increased the number of deformed leaves per plant compared with the nontreated control. This pattern was not observed in yr 2. In yr 1 and 2, two times the label rate of clopyralid (560 g ae ha−1) tended to reduce the total number of floral buds compared with the nontreated control by 12 to 17%. None of the herbicide rates or application times reduced the number of flowers per plant, marketable berries per plant, yield over time, or total yield. We conclude that clopyralid applications at the rates and application times tested in this study may cause leaf damage and may reduce leaf number in some situations but does not affect yield. Nomenclature: Clopyralid; strawberry, Fragaria × ananassa Duchesne. Malezas de hoja ancha anuales de invierno con semillas con testa dura emergen en los orificios del cultivo en la producción de fresa con coberturas plásticas en Florida, y reducen el rendimiento y la calidad de la fruta. Clopyralid está registrado para el control POST de malezas de hoja ancha, pero el daño del herbicida has sido observado en campos de producción comercial, y observaciones preliminares sugieren que los efectos varían dependiendo del momento de aplicación. Para analizar este problema, se realizó un experimento del 2012 al 2013 y del 2013 al 2014 para evaluar la dosis de clopyralid (0, 140, 280, y 560 g ae ha−1) y el momento de aplicación sobre el crecimiento vegetativo y reproductivo de la fresa. Las aplicaciones de clopyralid a 280 y 560 g ae ha−1, hechas el 2 y el 16 de Enero (primer año) redujeron el número de hojas por planta en 33 y 44% e incrementaron el número de hojas deformadas por planta al compararse con el testigo sin tratamiento. Este patrón no fue observado en el segundo año. Tanto en el primer como en el segundo año, el doble de la dosis de etiqueta de clopyralid (560 g ae ha−1) tendió a reducir el número total de brotes florales en comparación con el testigo sin tratamiento en 12 y 17%. Ninguno de las dosis del herbicida o los momentos de aplicación redujeron el número de flores por planta, las frutas comercializables por planta, el rendimiento a lo largo del tiempo, o el rendimiento total. Nosotros concluimos que las aplicaciones de clopyralid a las dosis y momentos de aplicación evaluados en este estudio podría causar daño foliar y podría reducir el número de hojas en algunas situaciones sin afectar el rendimiento.

Response of Diploid Watermelon to Imazosulfuron POST

Abstract Field trials were conducted to evaluate imazosulfuron applied POST at 0.1, 0.2, 0.3, and 0.4 kg/ha to watermelon at the two- to four-leaf stage or to vines 30.5 cm long. At 7 d after treatment (DAT), crop injury to watermelon increased linearly for both growth stages as rate increased. The least injury to watermelon observed 7 DAT was 19 and 15%, respectively, for the two- to four-leaf and 30.5-cm growth stages treated with 0.01 kg/ha imazosulfuron. The 0.4 kg/ha imazosulfuron treatment caused the greatest watermelon injury (approximately 30%) at both application timings. Yield of watermelon treated with 0.1 and 0.2 kg/ha imazosulfuron applied at the two- to four-leaf and 30.5-cm stages were similar to the nontreated check (all plots were maintained weed-free). For both application timings, yield decreased linearly as imazosulfuron rate increased. The application of imazosulfuron to watermelon at the 30.5-cm stage averaged across rates resulted in less injury at 15 DAT (16%) and greater yield (92,869 kg/ha) than watermelon treated at two- to four-leaf stage averaged across rates (29%, 83,560 kg/ha). Internal fruit quality was not affected by imazosulfuron.

Impact of Fallow Programs and Fumigants on Nutsedge (Cyperus spp.) Management in Plasticulture Tomato

Abstract With the loss of methyl bromide (MeBr) and high prices of alternatives, tomato growers are applying lower fumigant rates or adopting a reduced system. Without the broad-spectrum control provided by the complete fumigant system, a fallow weed program might be needed to avoid an increase in pest pressure with consecutive years of application of the reduced-fumigant system. Nutsedges are among the pests of interest due to their fast reproduction by underground structures and ability to spread and quickly infest a field. Field trials were conducted between February and December of 2011 in Balm, FL, to evaluate the impacts of fallow treatments, fumigants, and halosulfuron on nutsedge control. The trial design was a split–split plot with main, sub-, and subsubplots being fallow, fumigant, and herbicide treatment, respectively. Fallow treatments were spaced evenly throughout the fallow season and consisted of sequential combinations of cultivation (C) and/or glyphosate (G) applied at 2.24 kg ae ha−1; including: C, CC, G, GG, CG, GC, GCG, and NO (nontreated control). Fumigant treatments included a reduced-fumigant system of 1,3-dichloropropene plus chloropicrin 40:60 (1,3-D + pic) at 281 kg ha−1, a complete fumigant system of dimethyl disulfide plus chloropicrin 79:21 (DMDS + pic) at 545 kg ha−1, and no fumigant (NoFum). Herbicide treatments were either two POST applications of halosulfuron at 39 g ai ha−1 (Hal) or no halosulfuron (NoHal). In general, the fallow weed treatment GCG was the most effective in reducing nutsedge shoot emergence through the plastic mulch. When the reduced-fumigant system 1,3-D + pic was combined with GCG fallow treatment and halosulfuron (GCG:1,3-D + pic:Hal), no differences were found between this combination and the complete fumigant system DMDS + pic with halosulfuron and combined with CC, G, GG, CG, GC or GCG. This study shows the importance of adding a fallow weed program and halosulfuron to either a reduced or complete fumigation system to minimize the reproduction and growth of nutsedges. Nomenclature: Chloropicrin (pic); dimethyl disulfide (DMDS); glyphosate; halosulfuron; 1,3-dichloropropene (1,3-D); nutsedge, Cyperus spp.; tomato, Lycopersicon esculentum Mill. Resumen Con la pérdida de methyl bromide (MeBr) y los altos precios de las alternativas, los productores de tomate están aplicando dosis más bajas de fumigante o adoptando un sistema reducido. Sin el control de amplio espectro que se obtiene con un sistema de fumigación completo, un programa de manejo de malezas con barbecho limpio podría ser requerido para evitar el incremento en la presión de esta plaga en los años consecutivos a la aplicación del sistema de fumigación reducida. Cyperus spp. está entre las plagas de interés debido a su rápida reproducción por medio de estructuras subterráneas y su habilidad de dispersarse y rápidamente infestar un campo. Se realizaron experimentos de campo entre Febrero y Diciembre de 2011 en Balm, FL, para evaluar los impactos de tratamientos de barbecho, fumigantes, y halosulfuron sobre el control de Cyperus spp. El diseño del experimento fue parcelas divididas en dos niveles siendo el barbecho, el fumigante y el tratamiento del herbicida la parcela principal, la subparcela y la sub-subparcela, respectivamente. Los tratamientos de barbecho fueron distribuidos en forma uniforme a lo largo de la temporada de barbecho y consistieron en combinaciones secuenciales de cultivo con rastra de discos (C) y/o glyphosate (G) aplicado a 2.24 kg ae ha−1; incluyendo: C, CC, G, GG, CG, GC, GCG, y NO (testigo no tratado). Los tratamientos de fumigantes incluyeron un sistema de fumigación reducida de 1,3-dichloropropene más chloropicrin 40:60 (1,3-D + pic) a 281 kg ha−1, un sistema de fumigación completa de dimethyl disulfide más chloropicrin 79:21 (DMDS + pic) a 545 kg ha−1, y sin fumigante (NoFum). Los tratamientos de herbicidas fueron dos aplicaciones POST de halosulfuron a 39 g ai ha−1 (Hal) o sin halosulfuron (NoHal). En general, el tratamiento de barbecho GCG fue el más efectivo en reducir la emergencia de plantas de Cyperus spp. a través de la cobertura plástica. Cuando el sistema de fumigación reducida 1,3 + pic fue combinado con el tratamiento de barbecho GCG y halosulfuron (GCG:1,3-D + pic:Hal), no se encontraron diferencias entre esta combinación y el sistema de fumigación completa DMDS + pic con halosulfuron y combinado con CC, G, GG, CG, GC o GCG. Este estudio muestra la importancia de agregar un programa de barbecho y halosulfuron a sistemas de fumigación completa o reducida para minimizar la reproducción y crecimiento de Cyperus spp.

Spray Penetration into a Strawberry Canopy as Affected by Canopy Structure, Nozzle Type, and Application Volume

Strawberries, an important Florida crop, are grown on raised beds covered with plastic mulch. The plastic mulch provides good control of many weeds, but some problem species can emerge from the transplant hole during crop establishment. POST herbicide options for broadleaf weed control within the strawberry bed is limited to clopyralid, which only provides suppression. Strawberry canopy shielding may be responsible for the observed incomplete control with clopyralid application for problematic broadleaf weed species such as black medic and Carolina geranium. Two field experiments were established on mature strawberries to evaluate spray penetration through the canopy. The first examined spray penetration through the canopy of multiple strawberry cultivars at various distances from the crown. The second examined the effects of application volumes and nozzle selection on spray penetration. Cultivar selection had no effect on spray penetration through the canopy. In the first study, when applying at 281 L ha-1, the area around the planting hole (0 to 5 cm from the crown) had 8% coverage below the canopy while the area below the canopy edge (10 to 15 cm from the crown) had 27% coverage. In the second study, increasing the application volume from 187 to 375 L ha-1 increased coverage by 81%. Increasing the application volume from 375 to 740 L ha-1 increased coverage 33% with maximal coverage of 53% at 740 L ha-1. Nozzle type (standard even flat spray tip, Drift Guard, or TwinJet nozzles) did not affect coverage or deposition volume below the canopy. Overall, mature strawberry canopies demonstrated similar spray droplet penetration across cultivars with increased penetration with increased distance from the crown. Penetration increased with increasing application volume, but the nozzle types used in this experiment did not affect penetration. Additional research is needed to better define the effect of application volume on herbicide efficacy. Nomenclature: Strawberry, Fragaria × ananassa (Weston) Duchesne ex Rozier

Application Timing Influences Purple Nutsedge (Cyperus rotundus) and Yellow Nutsedge (Cyperus esculentus) Susceptibility to EPTC and Fomesafen

Purple and yellow nutsedge are problematic weeds in Florida small fruit and vegetable production. EPTC and fomesafen are PRE herbicides that suppress both nutsedge species, but field application in Florida has shown control to be erratic. Greenhouse experiments were conducted in Gainesville, FL, from May to August 2014 and in Wimauma, FL, from March to May 2015 to investigate susceptibility of purple and yellow nutsedge to EPTC and fomesafen applications. Treatments included EPTC at 2.91 kg ai ha−1 and fomesafen at 0.42 kg ai ha−1 at 0, 3, 6, 9, 12, and 15 d after planting (DAP) tubers, plus a nontreated control. EPTC and fomesafen applications averaged across timings decreased purple and yellow nutsedge emergence, shoot height, leaf number, and shoot mass compared to the nontreated control. Herbicide applications 0 DAP reduced purple nutsedge emergence greater than 65% compared to the nontreated control and caused at least 74% injury 4 wk after planting. Herbicide applications 0 DAP decreased yellow nutsedge emergence and shoot mass compared to the nontreated control by at least 86 and 93%, respectively. Applications of EPTC and fomesafen have the ability to suppress short-term purple and yellow nutsedge growth. Applications made at or prior to tuber sprouting maximize herbicide efficacy. Nomenclature: EPTC; fomesafen; purple nutsedge, Cyperus rotundus L.; yellow nutsedge, Cyperus esculentus L.