Gurinderbir S. Chahal

Influence of Glyphosate or Glufosinate Combinations with Growth Regulator Herbicides and Other Agrochemicals in Controlling Glyphosate-Resistant Weeds

Abstract With the forthcoming release of the 2,4-D- and dicamba-resistance traits stacked with either glyphosate or glufosinate resistance, the use of 2,4-D or dicamba alone or in tank mix with glyphosate or glufosinate likely will increase the control of glyphosate-resistant weeds in soybean. There also is an increasing trend among soybean growers to apply POST herbicides in combination with fungicides, insecticides, and fertilizers to reduce trips over the field. Greenhouse experiments were conducted during 2011 and 2012 to evaluate glyphosate or glufosinate applications with growth regulator herbicides and other agrochemicals for the control of glyphosate-resistant horseweed and glyphosate-resistant common lambsquarters. In most cases, glyphosate or glufosinate application with 2,4-D or dicamba provided 80% or more control of glyphosate-resistant horseweed and glyphosate-resistant common lambsquarters. These studies demonstrate that performance of glufosinate alone and with agrochemicals was poor on glyphosate-resistant common lambsquarters. However, no differences in glyphosate-resistant common lambsquarters biomass were noted among treatments including glufosinate alone, glufosinate plus growth regulator herbicides, and glufosinate plus growth regulator herbicides plus agrochemicals. The agrochemicals lambda-cyhalothrin, manganese, and pyraclostrobin did not affect weed control by glyphosate or glufosinate combinations with growth regulator herbicides. Visible soybean injury was noted at 1 wk after treatment (WAT) only when glufosinate was applied with lambda-cyhalothrin or pyraclostrobin but no differences in visible injury were seen with these combinations at 3 WAT. Nomenclature: 2,4-D; dicamba; glufosinate; glyphosate; lambda-cyhalothrin; manganese; pyraclostrobin; common lambsquarters, Chenopodium album L.; horseweed, Conyza canadensis (L.) Cronq.; soybean, Glycine max (L.) Merr. Resumen Con la próxima liberación de cultivos con resistencia a 2,4-D y dicamba en combinación con resistencia a glyphosate o glufosinate, es probable que el uso de 2,4-D o dicamba solos o en mezclas en tanque con glyphosate o glufosinate incrementará el control de malezas resistentes a glyphosate en soya. También, hay un tendencia creciente de que los productores apliquen herbicidas POST en combinación con fungicidas, insecticidas y fertilizantes para reducir el número de pases de aplicación en campo. Se realizaron experimentos de invernadero durante 2011 y 2012 para evaluar aplicaciones de glyphosate o glufosinate con herbicidas reguladores de crecimiento y otros agroquímicos, para el control de Conyza canadensis y Chenopodium album resistentes a glyphosate. En la mayoría de los casos, las aplicaciones de glyphosate o glufosinate con 2,4-D o dicamba brindaron 80% de control o más de C. canadensis y C. album resistentes a glyphosate. Estos estudios demostraron que el desempeño de glufosinate solo y con agroquímicos fue pobre sobre C. album resistente a glyphosate. Sin embargo, no se notaron diferencias en la biomasa de C. album resistente a glyphosate entre tratamientos incluyendo a glufosinate solo, glufosinate más herbicidas reguladores de crecimiento y glufosinate más herbicidas reguladores de crecimiento más agroquímicos. Los agroquímicos lambda-cyhalothrin, manganese y pyroclostrobin no afectaron el control de malezas al combinar glyphosate o glufosinate con herbicidas reguladores de crecimiento. El daño visible en la soya se notó a 1 semana después del tratamiento (WAT) solamente cuando glufosinate fue aplicado con lambda-cyhalothrin o pyraclostrobin, pero no se observaron diferencias en daño con estas combinaciones a 3 WAT.

The Effect of Cations and Ammonium Sulfate on the Efficacy of Dicamba and 2,4-D

Abstract Dicamba or 2,4-D will be used POST for the control of weeds in soybean when dicamba- or 2,4-D-resistant soybean are commercialized. The active ingredients of both herbicides are weak acids in solution and may bind to cations present from hard water used as herbicide carrier or from foliar fertilizers added to spray solutions. The objectives of this research were (1) to determine if the efficacy of dicamba or 2,4-D are influenced by divalent cations, namely calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn), in the spray solution, and (2) to determine if adding ammonium sulfate (AMS) to the spray solution can overcome antagonism. The factorial study included five cation solutions (deionized water [dH2O], Ca at 590 mg L−1, Mg at 630 mg L−1, Mn at 4.97 L ha−1, and Zn at 2.33 L ha−1), two herbicide treatments (dicamba or 2,4-D), and two water conditioner treatments (without or with AMS at 20.37 g L−1). Treatments were applied to common lambsquarters, horseweed, and redroot pigweed. Control of horseweed and redroot pigweed increased when AMS was added to the 2,4-D treatments, irrespective of cation solution. Control of common lambsquarters was increased when AMS was added to 2,4-D for only the Ca and Mn cation solution. In contrast to the results obtained with 2,4-D, control of horseweed with dicamba was not influenced by cation solution. Tank-mixing AMS with dicamba increased control of both redroot pigweed and common lambsquarters in the dH2O, Mg, and Mn solutions. Nomenclature: 2,4-D; dicamba; common lambsquarters, Chenopodium album L. CHEAL; horseweed, Conyza canadensis (L.) Cronq. ERICA; redroot pigweed, Amaranthus retroflexus L. AMARE. Resumen Dicamba o 2,4-D serán usados POST para el control de malezas en soya cuando se comercialice la soya resistente a dicamba o 2,4-D. Los ingredientes activos de ambos herbicidas son ácidos débiles en solución los cuales pueden adherirse a cationes provenientes de aguas pesadas usadas como medio de acarreo del herbicida o de fertilizantes foliares agregados a las soluciones de aplicación. Los objetivos de esta investigación fueron (1) determinar si la eficacia de dicamba o 2,4-D es influenciada por cationes divalentes, específicamente calcium (Ca), magnesium (Mg), manganese (Mn), y zinc (Zn), en la solución de aplicación, y (2) determinar si agregar ammonium sulfate (AMS) a la solución de aplicación puede eliminar los antagonismos. El estudio factorial incluyó cinco soluciones de cationes (agua desionizada [dH2O], Ca a 590 mg L−1, Mg a 630 mg L−1, Mn a 4.97 L ha−1, y Zn a 2.33 L ha−1), dos tratamientos de herbicidas (dicamba o 2,4-D), y dos tratamientos de acondicionamiento de aguas (sin o con AMS a 20.37 g L−1). Los tratamientos fueron aplicados a Chenopodium album, Conyza canadensis y Amaranthus retroflexus. El control de C. canadensis y de A. retroflexus incrementó cuando AMS fue agregado a los tratamientos de 2,4-D sin importar la solución de cationes. El control de C. album se incrementó cuando AMS fue agregado a 2,4-D pero solamente para las soluciones de los cationes Ca y Mn. En contraste con los resultados obtenidos con 2,4-D, el control de C. canadensis con dicamba no se vio influenciado por la solución de cationes. El mezclar en tanque AMS con dicamba incrementó el control de A. retroflexus y C. album en dH2O y soluciones de Mg y Mn.

Efficacy of Various Corn Herbicides Applied Preplant Incorporated and Preemergence

Abstract Field studies were conducted in central Missouri and central Kansas to evaluate the crop tolerance and efficacy of various combinations of atrazine, flufenacet + isoxaflutole, flumetsulam + clopyralid, isoxaflutole, and S-metolachlor applied PPI or PRE in conventional-till corn. Application technique did not influence crop injury in Kansas. In Missouri, greater crop injury was observed with treatments containing isoxaflutole when applied PPI vs. PRE. Application technique influenced giant foxtail, ivyleaf morningglory, large crabgrass, Palmer amaranth, and common waterhemp control. In dry years, control of these weeds was usually either same or greater with PPI than it was with PRE treatments. In years with average to above average precipitation, isoxaflutole provided greater control as a PRE application than as a PPI application. Palmer amaranth and common waterhemp control was usually greater with atrazine, isoxaflutole, and S-metolachlor applied PRE than it was applied PPI. Differences in control of all weeds between PPI and PRE applications were less obvious with two or three herbicides compared with treatments with a single herbicide. In general, the corn yield was greater with most of the treatments having two, three, or four herbicides than it was with treatments having a single herbicide, which was due to better weed control with the tank-mixtreatments. Nomenclature: Atrazine; clopyralid; flufenacet; flumetsulam; isoxaflutole; S-metolachlor; common waterhemp, Amaranthus rudis Sauer AMATA; giant foxtail, Setaria faberi Herrm. SETFA; ivyleaf morningglory, Ipomoea hederacea Jacq. IPOHE; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; corn, Zea mays L.

Influence of Water Quality and Coapplied Agrochemicals on Efficacy of Glyphosate

Abstract Experiments were conducted in 2008, 2009, and 2010 to determine the influence of water source as carrier and other agrochemicals on glyphosate efficacy and physicochemical compatibility. Glyphosate efficacy was not affected by most water sources, when compared with deionized water, although response was not consistent across all weed species, including cereal rye, common lambsquarters, common ragweed, goosegrass, Italian ryegrass, large crabgrass, Palmer amaranth, tall morningglory, and wheat. Control by glyphosate was not negatively affected when coapplied with cloransulam-methyl, dicamba, flumioxazin, pyrithiobac-sodium, thifensulfuron-methyl plus tribenuron-methyl, trifloxysulfuron-sodium, and 2,4-D but was affected by acifluorfen and glufosinate. Calcium, manganese, and zinc solutions consistently reduced weed control by glyphosate, whereas boron seldom affected efficacy. Compared with deionized water, Italian ryegrass control was affected by water sources when applied at seedling and jointing stages more so than at tillering and heading growth stages. Calcium, manganese, and zinc reduced control regardless of growth stage. Precipitates were not produced when glyphosate was applied with the water sources or fertilizer solutions. However, transient precipitates developed when glyphosate was coapplied with cloransulam-methyl, flumioxazin, thifensulfuron-methyl plus tribenuron-methyl, and trifloxysulfuron-sodium but not when coapplied with acifluorfen, dicamba, glufosinate, pyrithiobac-sodium, and 2,4-D. Solution pH ranged from 4.11 to 5.60 after glyphosate was added, regardless of solution pH before glyphosate addition. Nomenclature: 2,4-D; acifluorfen; boron; calcium; cloransulam-methyl; dicamba; flumioxazin; glufosinate; glyphosate; manganese; pyrithiobac-sodium; thifensulfuron-methyl plus tribenuron-methyl; trifloxysulfuron-sodium; zinc; cereal rye, Secale cereale L.; common lambsquarters, Chenopodium album L.; common ragweed, Ambrosia artemisiifolia L.; goosegrass, Eleusine indica (L.) Gaertn.; Italian ryegrass, Lolium perenne L. ssp. multiflorum (Lam.) Husnot.; large crabgrass, Digitaria sanguinalis (L.) Scop.; Palmer amaranth, Amaranthus palmeri (L.) S. Wats.; tall morningglory, Ipomoea purpurea (L.) Roth; wheat, Triticum aestivum L.

Compatibility of acephate with herbicides applied postemergence in peanut.

ABSTRACT Numerous agrochemicals can be applied in peanut to control pests. Field and laboratory experiments were conducted in North Carolina during 2009 and 2010 to determine peanut response to paraquat and tobacco thrips (Frankliniella fusca Hinds.) when acephate was applied in combination with chloroacetamide and contact herbicides. Experiments were also conducted during 2011 to determine peanut response to acephate applied alone or with paraquat when peanut was planted either without aldicarb or when aldicarb was applied in the seed furrow at planting. Visible peanut damage caused by tobacco thrips feeding was greater when chloroacetamide herbicides were applied without acephate compared with application with acephate regardless of paraquat treatment. Visible injury caused by paraquat was higher when chloroacetamide herbicides were included compared with paraquat alone in one of two years. Visible injury by paraquat was lower when applied with acephate compared to paraquat alone in one of two years. Ac...

Interactions of Clethodim and Sethoxydim with Other Pesticides

ABSTRACT A wide range of agrochemicals are applied in peanut to manage biotic and abiotic stresses. Experiments were conducted to evaluate the efficacy of clethodim and sethoxydim applied alone or with dimethenamid-P, pyraclostrobin, S-metolachlor, and 2,4-DB. When applied in combination with clethodim, pyraclostrobin often reduced goosegrass and large crabgrass control compared with clethodim only. Pyraclostrobin did not impact efficacy of sethoxydim in most instances. Dimethenamid-P and S-metolachlor did not negatively affect efficacy of clethodim and sethoxydim. The impact of 2,4-DB on efficacy of clethodim and sethoxydim was inconsistent. The magnitude of adverse impact on graminicides (clethodim and sethoxydim) performance did not exceed 19% and was caused primarily by pyraclostrobin. Conversely, increased efficacy of graminicides caused by chloroacetamide herbicides did not exceed 14%. Graminicides and chloroacetamide herbicides changed solution pH from slightly acidic to highly acidic. Several comb...