ABSTRACT Second-generation glyphosate-tolerant maize (Roundup Ready 2, RR2) is characterised by the expression of the cp4epsps gene. Despite some studies suggesting possible undesirable effects from the application of glyphosate in RR2 maize, other reports have demonstrated glyphosate selectivity for RR2 plants, with minor damage symptoms, if any, and with no negative effects on the chlorophyll indices. The aim of this study was to evaluate the effect of different types of glyphosate management, formulations and rates of application on chlorophyll indices and the agronomic performance of an RR2 maize genotype expressing the cp4epsps gene. Five experiments were conducted in a full factorial design (2 x 5 x 5) to evaluate two types of management, two formulations and five rates of glyphosate. Damage symptoms, chlorophyll indices and variables related to agronomic performance (plant height, stem diameter, yield and 100-grain weight) were evaluated. Similar crop responses were found for each of the glyphosate formulations (potassium salt and isopropylamine salt) and types of management (single application and sequential application) under test, indicating that the use of glyphosate-based commercial products affords flexibility in terms of formulation and frequency of application. Glyphosate formulated as potassium salt or isopropylamine salt and applied to RR2 maize either in a single application (full rate) or in two sequential applications (each at half rate) has a similar effect and may therefore be used without distinction. However, it is important to consider the rate of application since high rates of glyphosate (especially greater than 1,440 g ae ha-1) may affect the development and production of RR2 maize.

Abstract The aim was to investigate the differences between maize hybrids for their agronomic yield and their agro-energy potential. The study was conducted in Palotina and Assis Chateaubriand, Paraná, Brazil. The treatments were composed of 10 maize hybrids (DKB290 [non-GMO], DKB315, DKB340, DKB290, Formula, Defender, Status, 2B810, 30F53, BG7330), which were evaluated for grain moisture and yield, starch content, total soluble solids content, ethanol content in the juice and ethanol yield. The important factors for the result are related to grain yield and the quality of the harvested grains, and agronomic performance of these hybrids may differ according to each crop year. Hybrid 30F53 stood out positively for all variables. Hybrid DKB315 showed the highest ethanol yield and high grain yield, and insignificant grain quality was not enough to result in a decline in ethanol yield.

Resumen El objetivo de este estudio fue evaluar la eficacia de los herbicidas aplicados secuencial mente para controlar Conyza sumatrensis, una de las malezas más ampliamente distribuidas en todo el mundo, en la pre siembra de soja. El estudio se realizó en condiciones de campo en el estado de Paraná, Brasil, en la campaña 2018-2019. El experimento consistió en un diseño de bloques al azar con cuatro repeticiones, con 12 tratamientos compuestos por diferentes mezclas de herbicidas aplicados antes de la siembra. Se evaluó el control de C. sumatrensis, daño a plantas de soya y variables relacionadas con el comportamiento agronómico. Los niveles de control fueron altos para todos los tratamientos, excepto para el que estaba libre de saflufenacil en cualquiera de las dos aplicaciones. Estos resultados resaltan la importancia de saflufenacil en el control de C. sumatrensis y son prometedores para el uso de saflufenacil/imazethapyr cuando se considera el sistema y otras malezas. Todos los tratamientos estudiados fueron selectivos a la soja, que mostró mayores valores de daño en presencia de diclosulam; sin embargo, esto no comprometió el comportamiento agronómico de la soja.

Abstract The aim of this study was to evaluate the efficacy of sequentially applied herbicides to control Conyza sumatrensis, one of the most widely distributed weeds worldwide, in soybean pre-sowing burndown. The study was conducted under field conditions in the state of Paraná, Brazil, at 2018-2019 growing season. The experiment consisted of a randomized block design with four replicates, with 12 treatments consisting of different herbicide mixtures applied before sowing. Control of C. sumatrensis, injury to soybean plants, and variables related to agronomic performance were evaluated. The control levels were high for all treatments, except for the one that was free of saflufenacil in either of the two applications. These results highlight the importance of saflufenacil in the control of C. sumatrensis and show promise for the use of saflufenacil/imazethapyr when considering the system and other weeds. All studied treatments were selective to soybean, which showed higher injury values in the presence of diclosulam; however, this did not compromise the agronomic performance of soybean.

Abstract Agronomic science, like others in contemporary times, is marked by great achievements, technological bias, social importance and very prolific. However, the theoretical framework relevant to the philosophical reflection on agronomic science and its implications is scarce. In this sense, philosophical attention to its construction, scientific production and impacts on the creation of a philosophy of agronomy is justified. The objective of the present work was to analyze agronomic research and its generation of knowledge and technology, from the perspective of the philosophy of science. A bibliographic review was carried out based on a qualitative research work, through research in relevant literature, establishing an approximation with the objectives in a descriptive, interpretive, and critical way. The research axis was the theory of knowledge, in which epistemologically agronomy is predominantly empiricist, suffered positivist influences and can be relativized, not being autonomous and exempt. Scientific production in the agronomic area is the result of time and meets human demands, following the trends of society and being influenced by epistemological currents, in which the philosophy of agronomy can be built, which presents enormous challenges.

Resumo A ciência agronómica, como outras na contemporaneidade, é marcada por grandes conquistas, viés tecnológico, importância social e muito prolífica. No entanto, é carente o marco teórico pertinente à reflexão filosófica sobre a ciência agronómica e suas implicações. Nesse sentido, justifica-se atenção filosófica à sua construção, produção científico e impactos, na criação de uma filosofia da agronomia. O objetivo do presente trabalho foi analisar a pesquisa agronómica e sua geração de conhecimento e tecnologia, sob a ótica da filosofia da ciência. Foi conduzida uma revisão bibliográfica a partir de um trabalho de investigação qualitativa, por meio de pesquisa em literatura pertinente, estabelecendo uma aproximação com os objetivos de modo descritivo, interpretativo e crítico. O eixo de pesquisa foi à teoria do conhecimento, em que epistemologicamente a agronomia é preponderantemente empirista, sofreu influências positivistas e pode ser relativizada, não sendo autônoma e isenta. A produção científica na área agronómica é fruto do tempo e atende demandas humanas, seguindo as tendências da sociedade e sofrendo influência das correntes epistemológicas, no qual pode ser construída a filosofia da agronomia, que apresenta enormes desafios.

Resumen El objetivo del presente estudio fue investigar la posible influencia de la alelopatía de los extractos acuosos de cultivos forrajeros, aislados o en consorcio, sobre rendimiento fisiológico de las semillas de soja [Glycine max (L.) Merr.] y de maíz (Zea mays L.), además de su fitotoxicidad en la hierba Bidens pilosa L. Se prepararon extractos acuosos a una concen tración del 5%. Los estudios con soja y maíz se llevaron a cabo humedeciendo los papeles de germinación correspondientes a los diferentes tratamientos y se realizaron dentro de los estándares de las Reglas de Análisis de Semillas de Brasil. Estudios con los extractos en las semillas de B. pilosa se llevaron a cabo en una cámara de tipo B.O.D. Se colocaron cincuenta semillas de malezas en caja gerbox conteniendo papel de filtro humedecido con los diferentes tratamientos en cinco repeticiones. El agua destilada se utilizó como control en todas las pruebas. Los extractos de Avena strigosa y Raphanus sativus L., cultivados tanto en forma aislada como en consorcio, aumentaron el porcentaje de germinación de semillas (%G) y la longitud de las plántulas de soja. Asimismo, los extractos de Pennisetum glaucum (L.) R.Br. y Crotalaria spectabilis Roth, cultivados aislados y en consorcio, proporcionaron ganancias en el %G de maíz. Además, todos los extractos evaluados suprimieron la germi nación y redujeron la velocidad del índice de germinación de la maleza en comparación con el control, siendo el extracto de R. sativus el que más redujo el % G de B. pilosa.

Abstract The aim of the present study was to investigate the potential allelopathic effects of isolated or intercropped aqueous forage extracts on the physiological performance of soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) seeds, as well as their phytotoxicity to the weed species Bidens pilosa L. Aqueous extracts were prepared at a concentration of 5%, and the tests with soy and corn were conducted by wetting the germination papers with different treatments and performing procedures within the standards of the Brazilian Rules of Seed Analysis. Tests with the cover plant extracts on the seeds of B. pilosa used BOD-type repetitions. Fifty weed seeds were placed in a gerbox with filter paper moistened with the different treatments with five repetitions. Distilled water was used as the control in all tests. Extracts of Avena strigosa Schreb and Raphanus sativus L. (radish), cultivated individually and in combination, increased the seed germination percentage (%G) and the length of soybean seedlings. Similarly, extracts of Pennisetum glaucum (L.) R.Br and Crotalaria spectabilis Roth, in individual and combined cultivation, provided gains in corn %G. Furthermore, all tested extracts suppressed germination and decreased the speed of the germination index of the hairy beggarticks when compared to the control, with the radish extract showing the greater reduction effect on the %G of the weed plant B. pilosa.

ABSTRACT Glyphosate, glufosinate, and atrazine do not affect the growth and development of glyphosate and glufosinate-tolerant (RR2/ LL) maize; however, the results are less consolidated for these herbicides applied in mixtures. The aim of the present study was to evaluate the effects of post-emergent application of glyphosate, glufosinate, and atrazine, alone and in mixtures, on the growth and development of the RR2/LL maize. The treatments consisted of the application of glyphosate (1080 g of acid equivalent [ae] ha-1), glufosinate (500 g of active ingredient [ai] ha-1), atrazine (2000 g [ai] ha-1), glyphosate + glufosinate, glyphosate + atrazine, glufosinate + atrazine, glyphosate + glufosinate + atrazine, and the control (without application). The experiment was carried out in two locations under greenhouse conditions with different maize hybrids. Crop injury and variables of the agronomic performance (height, stem diameter, chlorophyll indexes, fresh and dry weight of shoot, root dry weight, and total dry weight) were evaluated. Herbicides applied alone or in binary mixtures did not cause major damage. However, the application of the three associated herbicides in some situations might result in detrimental effects on the development of the RR2/LL maize.

RESUMEN Glifosato, glufosinato y atrazina no afectan el crecimiento y desarrollo de las plantas de maíz tolerantes a glifosato y a glufosinato (RR2/LL); sin embargo, los resultados están menos consolidados para estos herbicidas aplicados en mezclas. El objetivo del presente estudio fue evaluar los efectos de la aplicación post-emergente de glifosato, glufosinato y atrazina, solos y en mezclas, sobre el crecimiento y desarrollo del maíz RR2/LL. Los tratamientos se formaron por aplicación de gli-fosato (1080 g de ácido equivalente [ae] ha-1), glufosinato (500 g de ingrediente activo [ia] ha-1), atrazina (2000 g [ai] ha-1), glifosato + glufosinato, glifosato + atrazina, glufosinato + atrazina, glifosato + glufosinato + atrazina, además del testigo (sin aplicación). El experimento se llevó a cabo en dos localidades, en condiciones de invernadero, con diferentes híbridos de maíz. Se evaluó la fitotoxicidad al cultivo y variables relacionadas con el crecimiento del mismo (altura, diámetro del tallo, índices de clorofila, masa fresca y seca de la parte aérea, masa seca de las raíces, masa seca total). Los herbicidas aplicados solos o en mezclas binarias, no causaron danos importantes. Sin embargo, la aplicación de los tres herbicidas en asociación en algunas situaciones puede resultar en efectos perjudiciales sobre el desarrollo del maíz RR2/LL.

ABSTRACT The use of glufosinate may have different effects on maize, with greater symptoms of injury for technologies with lower expression of the pat gene. As tolerance may vary with technology, it is important to investigate the selectivity of glufosinate in maize hybrids with the pat gene (resistant to insects). The objective of this study was to evaluate the selectivity of glufosinate rates applied in post-emergence, in insect-resistant transgenic maize with the pat gene. The experiment was carried out in Palotina, state of Paraná, Brazil, in 2020. A randomized block design with a factorial scheme (9x4) was used. The treatments were 9 maize hybrids and 4 glufosinate rates (0, 500, 700 and 1,000 g of active ingredient [ai] ha-1). Injury symptoms, plant height, 1,000-grain mass and yield were evaluated. The results showed that injury increases with increasing glufosinate rates. For plant height and 1,000-grain mass, a significant effect was detected only for hybrids, while there was no effect on yield, even at the highest rates. Glufosinate was selective for insect-resistant maize hybrids with the pat gene, up to the rate of 1,000 g ai ha-1, presenting initial injuries and some differences between maize hybrids. However, there was no impact on yield.

RESUMO Além dos herbicidas já registrados para a cultura do trigo, outros podem ser seletivos, como o saflufenacil, atrazine, mesotrione e triclopyr. Objetivou-se avaliar a seletividade de herbicidas em análise da produtividade de cultivo, isolados e em associações, aplicados em pós-emergência do trigo, no final do perfilhamento. Foram conduzidos dois experimentos utilizando-se delineamento de blocos casualizados, sendo o primeiro (E1) com 13 e o segundo (E2) com 7 tratamentos, compostos pela aplicação de 2,4-D, diclofop, iodosulfuron, clodinafop, saflufenacil, pyroxsulam, atrazine, mesotrione e triclopyr, isolados ou em associações. Foram avaliados sintomas de injúria no trigo, altura de plantas, número de espigas por planta, número de grãos por espiga, massa de 1.000 grãos e produtividade. A aplicação de diclofop e iodosulfuron foi seletiva ao trigo, com manutenção da produtividade mesmo sob as condições de estresse hídrico observadas no E1. Sob as mesmas condições, a aplicação de 2,4-D, clodinafop, saflufenacil, pyroxsulam, atrazine/ mesotrione, triclopyr ou saflufenacil + atrazine/mesotrione reduziu a produtividade do trigo, com diferentes níveis de injúria. Sob maior disponibilidade hídrica (E2), 2,4-D, clodinafop, saflufenacil, pyroxsulam e triclopyr foram seletivos ao trigo, sem efeito negativo à produtividade. A aplicação de atrazine/mesotrione apresentou elevado potencial de injúria para o cultivo e reduziu a produtividade do trigo.

ABSTRACT In addition to the herbicides already registered for the wheat crop, others may be selective, such as saflufenacil, atrazine, mesotrione and triclopyr. This study aimed to assess the selectivity of herbicides via crop yield analysis, alone and in mixtures, applied to wheat in post-emergence, at the end of tillering. Two experiments were conducted using a randomized blocks design. The first experiment (E1) involved 13 and the second one (E2) 7 treatments, consisting of the application of 2,4-D, diclofop, iodosulfuron, clodinafop, saflufenacil, pyroxsulam, atrazine, mesotrione and triclopyr, alone or in mixtures. Wheat injury symptoms, plant height, number of spikelets per plant, number of grains per spikelet, 1,000-grain weight and yield were assessed. The application of diclofop and iodosulfuron was selective to the wheat, maintaining yield even under the water stress conditions observed in E1. Under the same conditions, applying 2,4-D, clodinafop, saflufenacil, pyroxsulam, atrazine/mesotrione, triclopyr or saflufenacil + atrazine/mesotrione reduced the wheat yield, with different injury levels. Under greater water availability (E2), 2,4-D, clodinafop, saflufenacil, pyroxsulam and triclopyr were selective to the wheat, with no negative effect on yield. The application of atrazine/mesotrione showed a high injury potential for the crop and reduced the wheat yield.

RESUMO As associações de glufosinate com nicosulfuron, entre outros herbicidas, são promissoras no controle de plantas daninhas em pós-emergência do milho. Contudo alguns desses herbicidas podem causar injúrias e causar outros efeitos indesejáveis ao milho, assim é preciso se investigar a seletividade para o cultivo. Objetivou-se avaliar a seletividade de glufosinate, nicosulfuron e associações, em análise do desempenho agronômico do cultivo, para a aplicação em pós-emergência de híbridos de milho com gene pat. Dois experimentos foram conduzidos no estado do Paraná, Brasil, safra 2019/2020, em arranjo fatorial 2 x 8 (exp. I) e 2 x 4 (exp. II). Dois híbridos (FS505 PWU e FS715 PWU), oito níveis para o fator herbicida no experimento I (glufosinate, halosulfuron e glufosinate em associações com halosulfuron, nicosulfuron, atrazine, tembotrione ou mesotrione, além da testemunha sem aplicação) e quatro níveis para herbicidas no experimento II (nicosulfuron em duas formulações, mesotrione, além da testemunha) foram utilizados. Injúria nas plantas de milho e variáveis relacionadas ao desempenho agronômico foram avaliadas. Embora os herbicidas não tenham influenciado a produtividade, pode-se inferir que FS505 é mais sensível ao nicosulfuron e mesotrione que FS715, uma vez que a injúria observada foi maior que os observados em FS715. A aplicação em pós-emergência de glufosinate, nicosulfuron e associações é seletiva para os híbridos FS505 PWU e FS715 PWU (com gene pat). Apesar das injúrias, mais pronunciadas no híbrido FS505 PWU, não se observa impacto negativo sob a produtividade e outras variáveis de desempenho agronômico.

ABSTRACT Combinations of glufosinate with nicosulfuron, among other post-emergent herbicides, are promising for weed control in maize. However, some of these herbicides can cause injury and have other undesirable effects on the maize, so it is necessary to investigate their selectivity for cultivation. The aim of this study was to evaluate the selectivity of glufosinate, nicosulfuron and combinations, by analysing the agronomic performance of the crop for post-emergent application in maize hybrids with the pat gene. Two experiments were conducted in the state of Paraná, Brazil, during the 2019/2020 season, in a 2 x 8 (exp. I) and 2 x 4 (exp. II) factorial scheme. Two hybrids were used (FS505 PWU and FS715 PWU), with eight levels for the factor herbicide in experiment I (glufosinate, halosulfuron and glufosinate in combination with halosulfuron, nicosulfuron, atrazine, tembotrione or mesotrione, in addition to the control with no application) and four levels of herbicide in experiment II (nicosulfuron in two formulations, mesotrione, and the control). Injury to the maize plants and variables related to agronomic performance were evaluated. Although the herbicides had no effect on yield, it can be inferred that FS505 is more sensitive to nicosulfuron and mesotrione than is FS715, since the injury was greater than seen in FS715. The post-emergent application of glufosinate, nicosulfuron and combinations is selective for the FS505 PWU and FS715 PWU hybrids (with the pat gene). Despite injury, which was more pronounced in the FS505 PWU hybrid, there was no negative impact on yield or on other the variables of agronomic performance.

ABSTRACT Sumatran fleabane (Conyza sumatrensis [Retz.] E. Walker) can be found in many different agricultural environments and impact different crops, such as soybeans and corn. It is believed that the application of burndown and preemergence herbicides in the off-season are effective in controlling Sumatran fleabane in soybean crops. The objective was to evaluate the effectiveness of burndown and preemergence herbicides in the off-season, with one or two applications, in the control of Sumatran fleabane in soybean cultivation. Five field experiments were conducted in Maripá, state of Paraná (PR), Brazil. The treatments consisted of the application of burndown herbicides in combinations with preemergence ones, with one or two applications. Control of Sumatran fleabane and soybean yield were evaluated. With the set of experiments, it is highlighted that the strategy combining more applications, with different herbicides, burndown and preemergence, is more promising in the control of Sumatran fleabane. When comparing synthetic auxins, dicamba and triclopyr stand out. For sequential application, worse performance was observed for diquat. Combinations between burndown and preemergence herbicides were effective in controlling Sumatran fleabane, for pre sowing application in soybean. With emphasis on managements with sequential applications of saflufenacil with glufosinate or glyphosate. The strategy combining more applications, with different herbicides, burndown and preemergence herbicides, is more promising in the control of Sumatran fleabane.

Resumen Los herbicidas inhibidores de la ALS en combinación con inhibidores de la ACCase pueden ser utilizados como alternativa al glifosato en el control de malezas en soya RR2/STS. En el presente estudio se evalúa la eficacia de herbicidas inhibidores de la ALS, en asociación con haloxyfop, en el control de malezas para aplicación en post-emergencia (V4) de soya RR/STS. El experimento se realiza en la campaña 2017/18 en Piracicaba, Sao Paulo (SP), Brasil. Se utiliza el cultivar BMX Garra RR2/STS y los tratamientos fueron compuestos por la aplicación de herbicidas inhibidores de la ALS en asociación con haloxyfop. El diseño experimental fue de bloques al azar, con cuatro repeticiones. Se evaluaron control y masa seca de malezas, nivel de daño en las plantas de soya y productividad. Los datos fueron sometidos al análisis de varianza y las medias de los tratamientos fueron comparados por el test de Tukey. Se observaron síntomas visuales de daño en las plantas de soja, principalmente para aplicación de nicosulfuron y nicosulfuron + cloransulam. La productividad fue mayor en todos los tratamientos con herbicidas en comparación con el control sin deshierbe manual. Las asociaciones entre herbicidas inhibidores de la ALS y haloxyfop aplicadas en post emergencia (V4) del cultivar de soya BMX Garra RR2/STS fueron eficaces en el control de malezas.

Abstract It is believed that ALS inhibitor herbicides in combination with ACCase inhibitors can be used as an alternative to glyphosate in weed control in RR2/STS soybeans. In the present study, the efficacy of ALS inhibitor herbicides, in combination with haloxyfop, is evaluated in the control of weeds for post- emergence application (V4) of RR/STS soybeans. The experiment is carried out in the 2017/18 season in Piracicaba, Sao Paulo (SP), Brazil. The cultivar BMX Garra RR2/STS is used, and the treatments were composed by the application of ALS inhibitor herbicides in association with haloxyfop. The experimental design was a randomized block with four replications. Were evaluated control and dry mass of weeds, symptoms of injury in soybean plants and yield. The data were submitted to analysis of variance and the means of the treatments were compared by the Tukey test. Visual symptoms of injury were observed in soybean plants, mainly for the application of nicosulfuron and nicosulfuron + cloransulam. Soybean yield was higher in all herbicide treatments compared to the control without weeding. Associations between ALS inhibitor herbicides and haloxyfop applied post-emergence (V4) of soybean cultivar BMX Garra RR2/ STS were effective in weed control.

RESUMEN El pasto amargo (Digitaria insularis) es una de las principales malezas en el cultivo de soya. Para controlar su crecimiento, se requiere un aumento de las tasas de herbicida para simplificar su manejo al ser una planta con alta capacidad vegetativa y producción de semillas. Esto implica seleccionar los biotipos de Digitaria insularis resistentes a herbicidas Sin embargo, aún existe cierta información contrastante que considera el antagonismo de los herbicidas auxínicos sintéticos en las mezclas con inhibidores de ACCase y glifosato, para el control de malezas resistentes o tolerantes a los herbicidas. El estudio tuvo como objetivo evaluar el control de D. insularis con mezclas de herbicidas aplicados en la pre-emergencia y pos-emergencia del cultivo de soya y se verificó el posible antagonismo entre los herbicidas inhibidores de ACCase con auxinas sintéticas y otros latifolicidas. El experimento se realizó en Palotina, Paraná, (Brasil) y Corpus Christi, Canindeyú (Paraguay). Los tratamientos consistieron en mezclas de glifosato, inhibidores de ACCase (cletodim, haloxifop) y latifolicidas (2,4-D, triclopir, dicamba, carfentrazona, saflufenacil, clorimurón). Se utilizó un diseño de bloques al azar. El control de arvenses fue satisfactorio sólo en Palotina después de la aplicación secuencial en pos-emergencia. Allí se observó un control efectivo de D. insularis en la pre-emergencia, para algunas mezclas que presentaron glifosato+ACCase+carfentrazona, saflufenacil o clorimurón. Se observó antagonismo para todas las auxinas sintéticas en ambas ubicaciones. En Corpus Christi las mezclas de herbicidas no fueron efectivas, incluso con la aplicación de glifosato+cletodim en la pos-emergencia de soya. Aunque se obtuvo un control ineficaz para tratamientos compuestos con auxinas sintéticas, la aplicación en post-emergencia de soya aumentó el nivel de control, con resultados finales satisfactorios para todos los tratamientos.

ABSTRACT Sourgrass (Digitaria insularis) is one of the main weeds in the soybean crop. In order to control its growth, an increase of herbicide rates is required to simplify its management as it a plant with high vegetative capacity and seed production. It implies to select the herbicide-resistent Digitaria insularis biotypes. Nevertheless, some information is still contrasting the antagonist of synthetic auxinic herbicides, associated with glyphosate and ACCase inhibitors mixtures, for the control of weeds resistant or tolerant to herbicides. This study aimed to evaluate the D. insularis control, with a mixture of herbicides applied in soybean pre-emergence, with sequential application in soybean post-emergence, and to check possible antagonism between ACCase inhibitors herbicides with synthetic auxins and other latifolicides. The experiment was conducted in Palotina, Paraná (Brazil) and Corpus Christi, Canindeyú, (Paraguay.) The treatments consisted of associations of glyphosate, ACCase inhibitors (clethodim, haloxyfop), and latifolicides (2,4-D, triclopyr, dicamba, carfentrazone, saflufenacil, chlorimuron). A randomized block design was used. Only in Palotina, the weed control was satisfactory after sequential application in post-emergence. An antagonism for all synthetic auxins was observed with glyphosate+clethodim or haloxyfop mixtures, in both locations. As a result, in Palotina an efficacious control of perennial D. insularis was found in pre-emergence burndown for some mixtures such as glyphosate+ACCase inhibitor added to carfentrazone, saflufenacil, or chlorimuron. Antagonism was observed for all synthetic auxins, in both locations. In Corpus Christi, the herbicide associations were not effective, even with the post-emergence application in soybean of glyphosate+clethodim. With ineffective control for treatments composed with synthetic auxins, the post-emergence application in soybean increased the weed control with satisfactory final controls for all treatments.

RESUMEN Juntas, Conyza bonariensis, C. canadensis y C. sumatrensis presentan 105 casos reportados de biotipos resistentes a herbicidas tales como glifosato, paraquat y los inhibidores de la acetolactato sintasa (ALS). Se cree que la aplicación de herbicidas pre-emergentes en mezclas con desecantes es efectiva para controlar Conyza spp. en el manejo pre-siembra de la soya. El objetivo de este estudio fue evaluar la eficacia de sulfentrazona/ diuron, imazetapir/flumioxazin y diclosulam, en mezcla con diquat, paraquat o glufosinato, en el control de Conyza spp. Se realizaron dos experimentos de campo en diseño de bloques al azar con cuatro repeticiones. Los tratamientos consistieron en la aplicación de herbicidas pre-emergentes en mezclas con desecantes, además del tratamiento control (sin aplicación), para un total de 10 tratamientos. El control de Conyza spp. se evaluó a los 7, 14, 21, 28 y 35 d después de la aplicación del herbicida, y se evaluaron los síntomas de daño en las plantas de soya a los 14, 21, 28 y 35 d después de la aplicación del herbicida. Los herbicidas sulfentrazona/diuron, imazetapir/flumioxazin y diclosulam en mezclas con diquat, paraquat o glufosinato, fueron efectivos para controlar Conyza spp. en la pre-siembra de la soya, destacando buenas opciones para la rotación de herbicidas antes y después de la emergencia. Las mezclas con diclosulam mostraron un mayor potencial de daño a las plantas de soya que sulfentrazona/diuron y imazetapir/flumioxazin.

ABSTRACT Together, Conyza bonariensis, C. canadensis and C. sumatrensis show 105 reported cases of biotypes resistant to herbicides like glyphosate, paraquat, and acetolactate synthase (ALS) inhibitors . The application of pre-emergent herbicides combined with burndown herbicides is believed to be effective in controlling Conyza spp. during soybean pre-sowing management. The objective of this study was to evaluate the efficacy of sulfen-trazone/diuron, imazethapyr/flumioxazin, and diclosulam in mixtures with diquat, paraquat, or glufosinate on the control of Conyza spp. Two field experiments were conducted in a randomized block design with four replicates. Treatments consisted of the application of pre-emergent plus burndown herbicides, besides the weedy control treatment (without application), for a total of 10 treatments. The control of Conyza spp. was evaluated at 7, 14, 21, 28, and 35 d after herbicide application, and symptoms of injury in soybean plants were evaluated at 14, 21, 28, and 35 d after herbicide application. The herbicides sulfentrazone/diuron, imazethapyr/flumioxazin, and diclosulam in combination with burndown herbicides diquat, paraquat, or glufosinate were effective in controlling Conyza spp. in the pre-sowing management of soybean, highlighting good options for pre- and post-emergent herbicide rotations. Mixtures with diclosulam showed a higher potential for injury to soybean plants than sulfentrazone/diuron and imazethapyr/flumioxazin.

RESUMEN Las mezclas entre herbicidas, el uso de múltiples sitios de acción y otras prácticas de manejo de malezas son necesarias para evitar otros casos de resistencia de biotipos. El objetivo de este estudio fue evaluar la eficiencia de imazapic/imazapyr y otros herbicidas en mezclas para controlar Digitaria insularis en la desecación antes de la siembra de soya. Esta investigación de campo se realizó en Umuarama, Estado de Paraná (PR), Brasil, en la cosecha de soya de 2018/19. El experimento se realizó en un diseño experimental de bloques al azar, con cuatro repeticiones y 11 tratamientos, compuestos por la aplicación de glifosato, cletodim, haloxifop, imazapic/imazapir, glufosinato, ácido 2,4-diclorofenoxiacético (2,4-D), dicamba, triclopir y saflufenacil, en mezclas. Se evaluó el control de malezas, así como el daño y el rendimiento de la soya. Se realizaron un análisis de varianza y test F, y se compararon las medias de los tratamientos con el test de Scott-Knott. Todos los tratamientos mostraron un gran control sobre la maleza y una baja tasa de daño a los cultivos mientras se mantenía el rendimiento de la soya. La aplicación de imazapic/imazapir en mezclas con otros herbicidas fue eficaz en el control de D. insularis resistente al glifosato, en desecación antes de la siembra de soya y con aplicación secuencial de haloxifop + glifosato en la etapa V3 de la soya. Este manejo químico también fue selectivo para la soya.

ABSTRACT Herbicide mixtures, use of multiple sites of action, and other weed management practices are necessary to avoid cases of biotype resistance. The aim of this study was to evaluate the efficiency of imazapic/imazapyr and other herbicides in mixtures to control Digitaria insularis at burndown before soybean sowing. This field research was conducted in Umuarama, State of Parana (PR), Brazil, in the 2018/19 soybean season. The experiment was conducted in a randomized block experimental design with four replicates and 11 treatments composed of the application of glyphosate, clethodim, haloxyfop, imazapic/ imazapyr, glufosinate, 2,4-dichlorophenoxyacetic acid (2,4-D), dicamba, triclopyr, and saflufenacil, in mixtures. Weed control was evaluated as well as soybean injury and yield. An analysis of variance and F-test were performed, and the treatment means were compared by the Scott-Knott test. All treatments showed great control over the weed and low crop injury rate while maintaining soybean yield. The application of imazapic/ imazapyr in mixtures with other herbicides was effective in controlling glyphosate-resistant D. insularis in burndown before soybean sowing and with sequential application of haloxyfop + glyphosate at V3 stage of soybean. This chemical management was also selective for soybean.

RESUMEN El metsulfurón se usa ampliamente para el manejo de malezas, sin embargo, el efecto residual en los cultivares de soja STS es desconocido. El objetivo de este trabajo fue evaluar el efecto residual del herbicida metsulfurón en los cultivares de soja BMX Garra RR2/STS y M 6410 IPRO (no-STS). El metsulfurón se aplicó a una dosis de 2,4 g i.a. ha-1, en la pre-siembra de soja. El diseño experimental fue completamente aleatorio en un esquema factorial de 2x5 con cuatro repeticiones (primer factor: dos cultivares de soja - STS y no-STS y segundo factor: 5 períodos entre la aplicación y la siembra de soja - 0, 15, 30, 45 y 60 días). A los 7, 14, 21 y 28 días después de la siembra se realizó una evaluación de emergencia de las plántulas de soja, a los 28 días, se evaluó la altura y la masa seca de la parte aérea. Los promedios de altura para el cultivar STS fueron más altos que los valores del cultivar no-STS. La masa seca promedio de las plantas de soja fue mayor en el cultivar STS a los 0, 15 y 30 días entre la aplicación y la siembra. No se observaron diferencias entre los cultivares por los periodos de 45 y 60 días, para el promedio de masa seca. El cultivar de soja BMX Garra RR2/STS fue potencialmente tolerante para la aplicación previa a la siembra del metsulfurón. El cultivar de M 6410 IPRO (no-STS) tuvo su desarrollo inicial afectado por la aplicación de metsulfurón en preemergencia; sin embargo, la aplicación de metsulfurón de 60 días fue más segura y, por lo tanto, se recomienda realizar la aplicación de herbicida en ese intervalo de tiempo.

ABSTRACT Metsulfuron is widely used for weed management; however, the residual effect on STS soybean cultivars is unknown. The objective of this work was to evaluate the residual effect of the herbicide metsulfuron on the BMX Garra RR2/STS and M 6410 IPRO (non-STS) soybean cultivars. The herbicide metsulfuron was applied at a rate of 2.4 g a.i. ha-1, in pre-planting of soybean plants. The design was completely randomized in a 2×5 factorial scheme with four replications (first factor: two soybean cultivars - STS and no-STS; second factor: five periods between metsulfuron application and soybean sowing - 0, 15, 30, 45, and 60 days). At 7, 14, 21, and 28 days after sowing (DAS), an emergency evaluation of the soybean seedlings was performed; at 28 DAS, height and dry mass of the shoot were evaluated. The height averages for the STS cultivar were higher than the values of the no-STS cultivar. The average dry mass of soybean plants was higher in the STS cultivar at 0, 15, and 30 days between application and sowing. No differences were observed between the cultivars for the periods of 45 and 60 days, for average dry mass. The BMX soybean cultivar Garra RR2/STS was potentially tolerant for the pre-sowing application of the herbicide metsulfuron. The cultivar of M 6410 IPRO (non-STS) was affected in its initial development by the metsulfuron application during the pre-emergence stage; however, the 60-day metsulfuron application was safer, and therefore, it is recommended to perform the herbicide application in that interval.