Ryan S. Henry

Influence of Herbicide Active Ingredient, Nozzle Type, Orifice Size, Spray Pressure, and Carrier Volume Rate on Spray Droplet Size Characteristics

Abstract Recent concerns regarding herbicide spray drift, its subsequent effect on the surrounding environment, and herbicide efficacy have prompted applicators to focus on methods to reduce off-target movement of herbicides. Herbicide applications are complex processes, and as such, few studies have been conducted that consider multiple variables that affect the droplet spectrum of herbicide sprays. The objective of this study was to evaluate the effects of nozzle type, orifice size, herbicide active ingredient, pressure, and carrier volume on the droplet spectra of the herbicide spray. Droplet spectrum data were collected on 720 combinations of spray-application variables, which included six spray solutions (five herbicides and water alone), four carrier volumes, five nozzles, two orifice sizes, and three operating pressures. The laboratory study was conducted using a Sympatec laser diffraction instrument to determine the droplet spectrum characteristics of each treatment combination. When averaged over each main effect, nozzle type had the greatest effect on droplet size. Droplet size rankings for nozzles, ranked smallest to largest using volume median diameter (Dv0.5) values, were the XR, TT, AIXR, AI, and TTI nozzle with 176% change in Dv0.5 values from the XR to the TTI nozzle. On average, increasing the nozzle orifice size from a 11003 orifice to a 11005 increased the Dv0.5 values 8%. When compared with the water treatment, cloransulam (FirstRate) did not change the Dv0.5 value. Clethodim (Select Max), glyphosate (Roundup PowerMax), lactofen (Cobra), and glufosinate (Ignite) all reduced the Dv0.5 value 5, 11, 11, and 18%, respectively, when compared with water averaged over the other variables. Increasing the pressure of AIXR, TT, TTI, and XR nozzles from 138 to 276 kPa and the AI nozzle from 276 to 414 kPa decreased the Dv0.5 value 25%. Increasing the pressure from 276 to 414 kPa and from 414 to 552 kPa for the same nozzle group and AI nozzle decreased the Dv0.5 value 14%. Carrier volume had the least effect on the Dv0.5 value. Increasing the carrier volume from 47 to 187 L ha−1 increased the Dv0.5 value 5%, indicating that droplet size of the herbicides tested were not highly dependent on delivery volume. The effect on droplet size of the variables examined in this study from greatest effect to least effect were nozzle, operating pressure, herbicide, nozzle orifice size, and carrier volume. Nomenclature: Clethodim; cloransulam; glufosinate; glyphosate; lactofen. Resumen Recientemente ha habido preocupación por la deriva producto de la aplicación de herbicidas, su subsecuente efecto en el ambiente de los alrededores, y la eficacia del herbicida, lo que ha obligado a los aplicadores a enfocarse en métodos para reducir el movimiento de herbicidas a zonas fuera del objetivo deseado. Las aplicaciones de herbicidas son procesos complejos, y como tales, se han realizado pocos estudios que consideren múltiples variables que afectan el espectro de gotas producto de la aspersión del herbicida. Los objetivos de este estudio fueron elucidar los efectos del tipo de boquilla, el tamaño del orificio, el ingrediente activo del herbicida, la presión, y el volumen de aplicación sobre el espectro de gotas de la aspersión del herbicida. Los datos del espectro de gotas fueron colectados para 720 combinaciones de variables de aplicación-aspersión, las cuales incluyeron seis soluciones de aspersión (cinco herbicidas y agua sola), cuatro volúmenes de aplicación, cinco boquillas, dos tamaños de orificio, y tres presiones de operación. El estudio de laboratorio fue realizado usando un instrumento Sympactec de difracción láser para determinar las características del espectro de gotas para cada combinación de tratamientos. Al promediar los resultados por efecto principal, el tipo de boquilla tuvo el mayor efecto en el tamaño de gota. El ranking de tamaño de gota para boquillas, de más pequeña a más grande, usando valores de diámetro medio (Dv0.5), fue XR, TT, AIXR, AI, y TTI con 176% de cambio en los valores de Dv0.5. En promedio, el incrementar el tamaño del orificio de la boquilla de un orificio 11003 a uno 11005 aumentó los valores Dv0.5 en 8%. Cuando se comparó con el tratamiento con agua, cloransulam (FirstRate) no cambió el valor de Dv0.5. Clethodim (Select Max), glyphosate (Roundup PowerMax), lactofen (Cobra), y glufosinate (Ignite) redujeron los valores de Dv0.5 en 5, 11, 11, y 18%, respectivamente, cuando se compararon con agua al promediarse sobre las otras variables. El incrementar la presión de las boquillas AIXR, TT, TTI, y XR de 138 a 276 kPa y la boquilla AI de 276 a 414 kPa disminuyó el valor de Dv0.5 en 25%. El aumentar la presión de 276 a 414 kPa y de 414 a 552 kPa para el mismo grupo de boquillas y la boquilla AI disminuyó Dv0.5 en 14%. El volumen de aplicación tuvo el menor efecto en el valor de Dv0.5. Al aumentar el volumen de aplicación de 47 a 187 L ha−1 se incrementó el valor de Dv0.5 en 5%, indicando que el tamaño de gota de los herbicidas evaluados no fue altamente dependiente del volumen de aplicación. El efecto sobre el tamaño de gota de las variables examinadas en este estudio de mayor a menor efecto fue: boquilla, presión de operación, herbicida, tamaño del orificio de la boquilla, y el volumen de aplicación.

Performance of Postemergence Herbicides Applied at Different Carrier Volume Rates

Abstract POST weed control in soybean in the United States is difficult because weed resistance to herbicides has become more prominent. Herbicide applicators have grown accustomed to low carrier volume rates that are typical with glyphosate applications. These low carrier volumes are efficient for glyphosate applications and allow applicators to treat a large number of hectares in a timely manner. Alternative modes of action can require greater carrier volumes to effectively control weeds. Glyphosate, glufosinate, lactofen, fluazifop-P, and 2,4-D were evaluated in field and greenhouse studies using 47, 70, 94, 140, 187, and 281 L ha−1 carrier volumes. Spray droplet size spectra for each herbicide and carrier volume combination were also measured and used to determine their impact on herbicide efficacy. Glyphosate efficacy was maximized using 70 to 94 L ha−1 carrier volumes using droplets classified as medium. Glufosinate efficacy was maximized at 140 L ha−1 and decreased as droplet diameter decreased. For 2,4-D applications, efficacy increased when using carrier volumes equal to or greater than 94 L ha−1. Lactofen was most responsive to changes in carrier volume and performed best when applied in carrier volumes of at least 187 L ha−1. Carrier volume had little impact on fluazifop-P efficacy in this study and efficacy decreased when used on taller plants. Based on these data, applicators should use greater carrier volumes when using contact herbicides in order to maximize herbicide efficacy. Nomenclature: 2,4-D; Glufosinate; glyphosate; fluazifop-P; lactofen. Resumen El control de malezas POST en soya en los Estados Unidos es difícil porque la resistencia a herbicidas de las malezas se ha hecho más prominente. Los aplicadores de herbicidas se han acostumbrado a usar bajos volúmenes de aplicación que son típicos en aplicaciones con glyphosate. Estos bajos volúmenes de aplicación son eficientes para aplicaciones con glyphosate y permiten a los aplicadores tratar un gran número de hectáreas en poco tiempo. Modos de acción alternativos pueden requerir mayores volúmenes de aplicación para controlar malezas efectivamente. Glyphosate, glufosinate, lactofen, fluazifop-P, y 2,4-D fueron evaluados en estudios de campo y de invernadero usando volúmenes de aplicación de 47, 70, 94, 140, 187, y 281 L ha−1. Se midió el espectro de tamaño de gota de aspersión para cada combinación de herbicida y volumen de aplicación y se determinó su impacto en la eficacia del herbicida. La eficacia de glyphosate se maximizó usando volúmenes de 70 a 94 L ha−1 y gotas clasificadas como medianas. La eficacia de glufosinate se maximizó a 140 L ha−1 y disminuyó al reducirse el diámetro de gota. Para las aplicaciones de 2,4-D, la eficacia incrementó cuando se usaron volúmenes iguales o mayores a 94 L ha−1. Lactofen respondió más a los cambios en volumen de aplicación y se desempeñó mejor cuando fue aplicado con volúmenes de al menos 187 L ha−1. El volumen de aplicación tuvo poco impacto sobre la eficacia de fluazifop-P en este estudio y la eficacia disminuyó cuando se usó en plantas más altas. Con base en estos datos, los aplicadores deberían usar mayores volúmenes de aplicación cuando se usan herbicidas de contacto con el objetivo de maximizar la eficacia de los herbicidas.

The Impact of Spray Droplet Size on the Efficacy of 2,4-D, Atrazine, Chlorimuron-Methyl, Dicamba, Glufosinate, and Saflufenacil

Herbicide applications often do not reach their full potential because only a small amount of the active ingredients reaches the intended targets. Selecting the appropriate application parameters and equipment can allow for improved efficacy. The objective of this research was to evaluate the effect of droplet size on efficacy of six commonly used herbicides. Atrazine (1.12 kg ai ha−1), cloransulam-methyl (0.18 g ai ha−1), dicamba (0.14 kg ae ha−1), glufosinate (0.59 kg ai ha−1), saflufenacil (12.48 g ai ha−1), and 2,4-D (0.20 kg ae ha−1) were applied to seven plant species using an XR11003 nozzle at 138, 276, and 414 kPa and a AI11003 nozzle at 207, 345, and 483 kPa. Each herbicide, nozzle, and pressure combination was evaluated for droplet size spectra. Treatments were applied at 131 L ha−1 to common lambsquarters, common sunflower, shattercane, soybean, tomato, velvetleaf, and volunteer corn. Control from 2,4-D was observed to increase approximately 12% on average for all species except common lambsquarters as droplet size increased from medium to very coarse (Dv0.5 303 to 462 μm; Dv0.5 is droplet size such that 50% of spray volume is contained in droplets of equal or smaller size). Control with atrazine was near 95% for common lambsquarters, common sunflower, and soybean. Atrazine provided the greatest shattercane control using a medium (Dv0.5 325 μm) droplet, whereas the same droplet size provided the lowest tomato control. Control of common lambsquarters, shattercane, and tomato with cloransulam-methyl increased 79% when decreasing droplet size from extremely coarse to fine (Dv0.5 637 to 228 μm). Dicamba control of common lambsquarters increased 17% using a medium droplet compared with a fine droplet (Dv0.5 279 to 204 μm). Dry weight of common sunflower and soybean was reduced 21% using dicamba when using a very coarse spray compared with a fine spray classification (Dv0.5 491 to 204 μm). Common lambsquarters control using glufosinate increased 18% using a fine spray classification (Dv0.5 186 μm) compared with medium (Dv0.5 250 μm) and both very coarse droplet sizes (Dv0.5 470 and 516 μm). Conversely, tomato and velvetleaf control with glufosinate was maximized using a very coarse (Dv0.5 470 and 516 μm) or extremely coarse droplet (Dv0.5 628 μm) with increases of 11 and 25% compared with a fine spray (Dv0.5 186 μm). Saflufenacil control of volunteer corn was 38% greater using extremely coarse droplets (Dv0.5 622 μm) than fine, medium, and very coarse spray classifications (Dv0.5 257 to 514 μm). Overall, spray classifications for the herbicides evaluated play an important role in herbicide efficacy and should be tailored to the herbicide being used and the targeted weed species. Nomenclature: Atrazine; cloransulam-methyl; 2,4-D; dicamba; glufosinate; saflufenacil; common lambsquarters, Chenopodium album L.; common sunflower, Helianthus annus L.; shattercane, Sorghum bicolor (L.) Moench ssp. arundinaceum (Desv.) de Wet & Harlan; soybean, Glycine max (L.) Merr.; tomato, Solanum lycopersicum L.; velvetleaf, Abutilon theophrasti Medik.; volunteer corn, Zea mays L. Las aplicaciones de herbicidas a menudo no alcanzan su máximo potencial porque solamente una pequeña cantidad de los ingredientes activos alcanzan los objetivos deseados. El seleccionar los parámetros de aplicación y equipo apropiados puede permitir una mejora en la eficacia. El objetivo de esta investigación fue evaluar el efecto del tamaño de gota sobre la eficacia de seis herbicidas de uso común. Atrazine (1.12 kg ai ha−1), cloransulam-methyl (0.18 g ai ha−1), dicamba (0.14 kg ae ha−1), glufosinate (0.59 kg ai ha−1), saflufenacil (12.48 g ai ha−1), y 2,4-D (0.20 kg ae ha−1) fueron aplicados a siete especies de plantas usando una boquilla XR11003 a 138, 276, y 414 kPa y una boquilla AI11003 a 207, 345, y 483 kPa. Cada herbicida, boquilla, y combinación de presión fue evaluada para determinar el espectro de tamaño de gota. Los tratamientos fueron aplicados a 131 L ha−1 a Chenopodium album, girasol, Sorghum bicolor ssp. arundinaceum, soja, tomate, Abutilon theophrasti, y maíz voluntario. Se observó que el control con 2,4-D aumentó en promedio aproximadamente 12% para todas las especies, excepto para C. album, al aumentarse el tamaño de gota de medio a muy grande (Dv0.5 303 a 462 μm; Dv0.5 es el tamaño de gota al cual el 50% del volumen de aplicación es contenido en gotas de igual o menor tamaño). El control con atrazine fue cercano al 95% para C. album, girasol, y soja. Atrazine brindó el mayor control de S. bicolor usando gotas de tamaño mediano (Dv0.5 325 μm), mientras que el mismo tamaño de gota brindó el menor control de tomate. El control de C. album, S. bicolor, y tomate con cloransulam-methyl aumentó 79% cuando disminuyó el tamaño de gota de extremadamente grande a fino (Dv0.5 637 a 228 μm). El control de C. album con dicamba aumentó 17% usando gotas medianas al compararse con gotas finas (Dv0.5 279 a 204 μm). El peso seco del girasol y la soja se redujo 21% con dicamba cuando se asperjó con gotas muy grandes al compararse con la clasificación fina (Dv0.5 491 a 204 μm). El control de C. album con glufosinate aumentó 18% usando la clasificación fina de aspersión (Dv0.5 186 μm) al compararse con los tamaños de gota mediano (Dv0.5 250 μm) y las dos clasificaciones muy grande (Dv0.5 470 y 516 μm). En cambio, el control del tomate y A. theophrasti con glufosinate fue maximizado al usar gotas de tamaño muy grande (Dv0.5 470 y 516 μm) o extremadamente grande (Dv0.5 628 μm) con incrementos de 11 y 25% al compararse con la aspersión fina (Dv0.5 186 μm). El control de maíz voluntario con saflufenacil fue 38% mayor al usarse gotas extremadamente grandes (Dv0.5 622 μm) que con las clasificaciones de aspersión fina, mediana, y muy grande (Dv0.5 257 y 514 μm). En general, las clasificaciones de aspersión para los herbicidas evaluados juegan un rol importante en la eficacia del herbicida y deberían ser escogidas según el herbicida a usar y las especies de malezas que se desean controlar.

Spray Drift from Dicamba and Glyphosate Applications in a Wind Tunnel

With the recent introductions of glyphosate- and dicamba-tolerant crops, such as soybean and cotton, there will be an increase in POST-applied tank-mixtures of these two herbicides. However, few studies have been conducted to evaluate drift from dicamba applications. This study aimed to evaluate the effects of dicamba with and without glyphosate sprayed through standard and air induction flat-fan nozzles on droplet spectrum and drift potential in a low-speed wind tunnel. Two standard (XR and TT) and two air induction (AIXR and TTI) 110015 nozzles were used. The applications were made at 276 kPa pressure in a 2.2ms-1 wind speed. Herbicide treatments evaluated included dicamba alone at 560 g ae ha-1 and dicamba + glyphosate at 560 + 1,260 g ae ha-1. The droplet spectrum was measured using a laser diffraction system. Artificial targets were used as drift collectors, positioned in a wind tunnel from 2 to 12 m downwind from the nozzle. Drift potential was determined using a fluorescent tracer added to solutions, quantified by fluorimetry. Dicamba droplet spectrum and drift depended on the association between herbicide solution and nozzle type. Dicamba alone produced coarser droplets than dicamba + glyphosate when sprayed through air induction nozzles. Drift decreased exponentially as downwind distance increased and it was reduced using air induction nozzles for both herbicide solutions. Nomenclature: Dicamba; glyphosate; cotton, Gossypium hirsutum L.; soybean, Glycine max (L.) Merr.

A Comparison of an Unhooded and Hooded Sprayer for Pesticide Drift Reduction

Management of drift from pesticide applications is important for human and environmental health concerns. It is also necessary to ensure adequate dosage of the pesticide meets the target species(s). A variety of factors can affect the drift potential of a pesticide application, including nozzle selection, solution chemistry, and application equipment. In the present study, a comparison of two ground sprayers, one with a hood and one without a hood, is made using three common ground nozzles in the US. The hooded sprayer reduced the drift potential of the pesticide application for all nozzles tested. In addition, higher spray coverage under the boom was measured when using the hooded sprayer. The results of this study indicate that incorporating a hood will lead to reduced drift potential from a pesticide application.

Herbicide Spray Penetration into Corn and Soybean Canopies Using Air-Induction Nozzles and a Drift Control Adjuvant

Abstract Drift reduction technologies aim to eliminate the smaller droplets that occur with some sprays because these small droplets can move off-target in the wind. Commonly used drift reduction technologies such as air-induction nozzles and spray additives impact on reducing off-target movement is well documented, however, the impact on herbicide penetration into an established crop canopy is not well known. This experiment evaluated the canopy penetration and efficacy of glyphosate treatments applied using four nozzle types (XR11005, AIXR11005, AITTJ11005, and TTI11005), two carrier volume rates (94 and 187 L ha-1), and glyphosate applications with and without a commercial drift reducing adjuvant. Applications were made to corn and soybean fields using glyphosate applied at 1.26 kg ae ha-1 with liquid ammonium sulfate at 5% v/v. A rhodamine dye was added (0.025% v/v) to the spray tank of each mixture as a tracer. Mylar™ cards were placed in the field above the canopy, in the middle canopy, and on the ground for corn and above and below canopy for soybean. Five cards were at each position in the canopy arranged across the crop row. The addition of a drift reducing adjuvant did not impact canopy penetration. Doubling the carrier volume increased the amount of penetration proportionally and as such the percent reduction was not different. The TTI11005 nozzle had the greatest amount of spray penetration (28%) in the soybean canopies and the XR nozzle had the greatest amount (50%) in the corn canopies. Deposition across the row, beginning in-between the row crop and ending in the row of the crop was 44, 18, and 8% for soybean and 59, 50, and 36% for corn. For both crops, more than half of the herbicide application was captured in the crop canopy. Proper nozzle selection for canopy type can increase herbicide penetration and increasing the carrier volume will increase penetration proportionally. Nomenclature: Glyphosate; corn, Zea mays L; soybean, Glycine max (L.) Merr

The Effect of Adjuvants at High Spray Pressures for Aerial Applications

Controlling droplet size is a critical part of making any successful agrochemical spray application. This is particularly true for higher-speed aerial applications where secondary atomization from air shear becomes the most dominant factor driving spray droplet size. Previous research has shown that higher spray pressures can result in larger droplet-sized sprays by increasing the exit velocity of the spray liquid from the nozzles, which in turn decreases the differential velocity between the spray liquid and surrounding airstream, reducing secondary breakup. This work explores the effects of higher-than-normal spray pressures on two typical aerial application nozzles in the presence of a formulated herbicide spray solution, with and without additional adjuvants. Generally, the spray solution effects followed trends seen in previous studies, with crop oil-containing adjuvants resulting in the largest droplet-sized sprays and the silicones and polymers the smallest. Increasing spray pressure increased droplet size across all combinations of nozzle, airspeed, and spray solution, without exception. The most promising results from this work showed that for typical high-end application airspeeds, increasing spray pressure from the lowest to highest pressures tested generally resulted in spray classifications increasing at least one Manuscript received October 22, 2015; accepted for publication May 18, 2016. U.S. Department of Agriculture, Agricultural Research Service, 3103 F&B Rd., College Station, TX 77845 University of Nebraska, Pesticide Application Technology Research and Extension Lab, 402 W. State Farm Rd., North Platte, NE 69101 ASTM 36th Symposium on Pesticide Formulation and Delivery Systems: Emerging Trends Building on a Solid Foundation on October 27–29, 2015 in Tampa, Florida. Copyright VC 2016 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. PESTICIDE FORMULATION AND DELIVERY SYSTEMS: 36TH VOLUME 133 STP 1595, 2016 / available online at www.astm.org / doi: 10.1520/STP159520150086 size coarser. The results from this work demonstrate that larger, faster-flying agricultural aircraft can adopt current methods, with potentially minor equipment adjustments, to generate medium and larger spray qualities and to allow for more efficient applications while meeting agrochemical product label requirements.

Physical and Biological Effects of Modified Polysorbate 20

Three experimental polyoxyethylene sorbitan monolaurate derivatives were synthesized with molecular fingerprinting techniques applied to experimental materials, confirming the target compounds had been produced. Chemical property measurements were compiled that aligned with theoretical predictions and physical property measurements confirmed their intentional differences yielded the anticipated changes in surfactant behavior. Imidacloprid uptake data confirmed penetration of leaf cuticles was enhanced in the presence of polyoxyethylene sorbitan monolaurates with several experimental materials providing uptake equivalent to reference material. Select materials were included in field and greenhouse trials where observations included good biological response with a range of individual herbicides as well as improved control of volunteer glyphosate tolerant corn with mixtures of glyphosate and clethodim over the control nonionic surfactant adjuvant when applied as a tank-added adjuvant. Antagonism of annual grass control was not observed. Manuscript received December 15, 2013; accepted for publication December 16, 2014; published online February 24, 2015. Croda Inc., New Castle, DE 19720. Southern Illinois Univ., Carbondale, IL 62901. Univ. of Nebraska at Lincoln, North Platte, NE 68588. ASTM 34th Symposium on Pesticide Formulation and Delivery Systems: Translating Basic Science into Products on Oct. 22–24, 2013 in Jacksonville, FL. Copyright VC 2015 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. PESTICIDE FORMULATION AND DELIVERY SYSTEMS: 34TH VOLUME, TRANSLATING BASIC SCIENCE INTO PRODUCTS 76 STP 1579, 2015 / available online at www.astm.org / doi: 10.1520/STP157920130188