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.

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.

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 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.

Abstract Background: Other tools for weed management should be considered in addition to the use of herbicides. In this context, the identification and use of allelopathic compounds deserves attention. Question: To quantify phenolic compounds and evaluate the allelopathic potential of extracts of Conyza sumatrensis on the germination of Bidens pilosa. Studied species: Conyza sumatrensis (Retz.) E.Walker, Bidens pilosa L. (Asteraceae) Study site: Palotina, state of Paraná, Brazil. Methods: The aqueous extracts were prepared with shoot and root portions of C. sumatrensis in concentrations: 0, 1, 5 and 10 %. Germination and germination speed index were evaluated. The total flavonoids and phenols of the tested extracts were also quantified. Results: With increasing concentrations of the extracts there was an increased inhibition of germination of B. pilosa and delays in the germination process. The extracts from the shoot of C. sumatrensis had a more expressive effect on seed germination when compared to the extracts obtained from the root. At concentration of 10 %, the extract from the shoot reduced in 83 % the percentage of germination. This may be related to the higher concentration of total flavonoids and phenols found. Conclusion: The allelopathic potential of C. sumatrensis plants can be considered since both shoot and root extracts inhibited and/or reduced the germination of B. pilosa.

Resumen Antecedentes: Se deben considerar otras herramientas para el manejo de malezas además del uso de herbicidas. En este contexto, la identificación y el uso de compuestos alelopáticos merece atención. Problema: Cuantificar compuestos fenólicos y evaluar el potencial alelopático de extractos de Conyza sumatrensis en la germinación de Bidens pilosa. Especies de estudio: Conyza sumatrensis (Retz.) E.Walker, Bidens pilosa L. (Asteraceae) Sitio de estudio: Palotina, estado de Paraná, Brasil. Métodos: Los extractos acuosos se prepararon con porciones de brotes y raíces de C. sumatrensis en concentraciones: 0, 1, 5 y 10 %. Se evaluaron la germinación y el índice de velocidad de germinación. También se cuantificaron los flavonoides y fenoles totales de los extractos probados. Resultados: Con el aumento de las concentraciones de los extractos hubo una mayor inhibición de la germinación de B. pilosa y retrasos en el proceso de germinación. Los extractos del brote de C. sumatrensis tuvieron un efecto más expresivo sobre la germinación de las semillas en comparación con los extractos obtenidos de la raíz. En la concentración de 10 %, el extracto del brote redujo en 83 % el porcentaje de germinación. Esto puede estar relacionado con la mayor concentración de flavonoides y fenoles totales encontrados. Conclusión: El potencial alelopático de las plantas de C. sumatrensis puede considerarse ya que tanto los extractos de brotes como los de raíz inhibieron y/o redujeron la germinación de B. pilosa.

RESUMO: Há poucas informações sobre a eficácia e seletividade de sulfonilureias, isoladas e associadas ao glifosato, na soja tolerante ao glifosato e às sulfonilureias. Assim, o presente estudo teve como objetivo avaliar a eficácia no controle de plantas daninhas e seletividade de sulfonilureias, isoladas e em associação com o glifosato, em pós-emergência (V4) de soja RR2/STS. Os experimentos foram conduzidos em áreas localizadas nos municípios de Piracicaba, São Paulo (SP), Brasil (experimento I) e Palotina, Paraná (PR), Brasil (experimento II). Os tratamentos foram compostos pela aplicação dos herbicidas sulfometurom, clorimurom, halossulfurom, etoxissulfurom e glifosato, isolados e em associação, no cultivar BMX Garra RR2/STS. O experimento I foi realizado com o foco principal na avaliação da eficácia no controle de plantas daninhas; ao passo que o experimento II se concentrou principalmente na avaliação da seletividade dos herbicidas. O delineamento experimental foi o de blocos casualizados, com quatro repetições. Foram avaliados sintomas de injúria, controle de plantas daninhas e variáveis relacionadas ao desempenho agronômico. Os dados foram submetidos à análise de variância, e as médias dos tratamentos foram comparadas pelo teste de Tukey. Sulfonilureias associadas ao glifosato foram eficazes no controle de plantas daninhas e seletivas para o cultivar de soja BMX Garra RR2/STS. A associação sulfometurom + clorimurom + glifosato apresentou potencial fitotóxico para o cultivar BMX Garra RR2/STS.

ABSTRACT: There is little information on the efficacy and selectivity of sulfonylureas, isolated and in association with glyphosate, in glyphosate and sulfonylurea-tolerant soybeans. Thus, the present study aims to evaluate the efficacy of weed control and selectivity of sulfonylureas, isolated and in association with glyphosate, at post-emergence (V4) of RR2/STS soybean. The experiments were conducted in the in areas located in Piracicaba City, São Paulo State (SP), Brazil (experiment I) and Palotina City, Paraná State (PR), Brazil (experiment II). Treatments were composed of application of the herbicides sulfometuron, chlorimuron, halosulfuron, ethoxysulfuron and glyphosate, isolated and in association, in the BMX Garra RR2/STS cultivar. Experiment I was conducted focusing on the evaluation of the efficacy of weed control; whereas experiment II focused mainly on the evaluation of herbicide selectivity. The experimental design was the randomized complete block, with four replications. Crop injury, weed control, and variables related to agronomic performance were evaluated. Data were submitted to analysis of variance, and the means of the treatments were compared with the Tukey test. Sulfonylureas in association with glyphosate were effective in weed control and selective for the BMX Garra RR2/STS soybean cultivar. The sulfometuron + chlorimuron + glyphosate association presented phytotoxic potential for the BMX Garra RR2/STS cultivar.

ABSTRACT. Fleabane (Conyza spp.) is an important weed in grain production systems and is currently one of the most problematic weeds in Brazil. An important factor related to weeds such as fleabane is the characteristic of herbicide-resistant biotypes developed under selection pressure, with multiple resistance previously detected for Conyza spp. Thus, the aim of this study was to demonstrate the multiple resistance of Conyza sumatrensis to the herbicides paraquat, glyphosate, and chlorimuron. From the F2 seeds of biotypes with suspected resistance to paraquat, glyphosate, and chlorimuron, dose-response greenhouse experiments were conducted for the three herbicides. Herbicides were applied when the plants had 6-8 leaves that were at a height of 8 cm. At the end of the evaluations, 28 days after application, multiple resistance to paraquat, glyphosate, and chlorimuron was observed, with resistance factors (RF50) for the control of 7.43, 3.58, and 14.35 and for the reduction of dry mass of 2.65, 2.79, and 11.31, respectively. All the established criteria for demonstrating new cases of weed resistance were met; thus, the first case worldwide of a Conyza species with resistance to herbicides with three different mechanisms of action was confirmed.

RESUMO: A planta daninha Conyza spp. está entre as principais encontradas em todo o mundo. Devido a sua agressividade, como elevada produção e dispersão de sementes e os crescentes relatos de biótipos resistentes ao glyphosate, paraquat e outros herbicidas, faz-se necessário o uso de diferentes ferramentas de manejo. Assim, o objetivo deste estudo foi avaliar a eficácia de herbicidas com aplicação sequencial de glufosinate em pré-semeadura da soja, no controle de Conyza spp. com indicativo de resistência ao paraquat. O estudo foi realizado em campo nos municípios de Assis Chateaubriand e Palotina, estado do Paraná (PR), Brasil, na safra 2018/19. O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições. Os tratamentos foram compostos pela aplicação de glyphosate, 2,4-D, saflufenacil, glufosinate, saflufenacil/imazethapyr, diclosulam, paraquat/diuron, paraquat e imazethapyr/flumioxazin, em diferentes combinações em pré-semeadura da soja. Foram avaliados controle de Conyza spp., sintomas de injúria nas plantas de soja e variáveis relacionadas ao desempenho agronômico (altura de plantas e produtividade). Todos os tratamentos mostraram-se seletivos a soja. Visualizou-se maiores sintomas de injúria quando se tinha a presença do herbicida diclosulam, mas não resultou em danos ao desempenho agronômico da soja. De forma geral os níveis de controle foram altos para os tratamentos utilizados, em exceção para os tratamentos com paraquat na área que apresentava maior frequência de Conyza spp. com indicativo de resistência a este herbicida, e para o tratamento com imazethapyr/flumioxazin nas duas áreas. Estes resultados de controle enfatizam a importância do glufosinate neste sistema de manejo e demostram resultados promissores para saflufenacil/imazethapyr.

ABSTRACT: Conyza spp. is among the main weeds reported worldwide. Due to its aggressiveness, such as high seed production and dispersion, and the growing reports of biotypes resistant to glyphosate, paraquat, and other herbicides, different control practices are required. Thus, this study aimed to evaluate the efficacy of herbicides with sequential application of glufosinate in soybean pre-sowing for control of Conyza spp. with indicative of resistant to paraquat. The study was carried out in the field, at Assis Chateaubriand and Palotina, state of Paraná, Brazil, in the 2018/19 season. The experiments were conducted in a randomized block design with four replications. The treatments consisted in application of glyphosate, 2,4-D, saflufenacil, glufosinate, saflufenacil/imazethapyr, diclosulam, paraquat/diuron, paraquat and imazethapyr/flumioxazin, at different combinations, in soybean pre-sowing. Control of Conyza spp., crop injury to soybean plants and variables related to agronomic performance (plant height and yield) were evaluated. All treatments were selective for soybean, which showed stronger crop injury in the presence of diclosulam herbicide, but this did not compromise soybean agronomic performance. In general, control levels were high for the treatments used. Except for paraquat treatments, in the area with the highest frequency of Conyza spp. with indicative of resistant to paraquat, and imazethapyr/flumioxazin treatment in both areas. These control results emphasized the importance of glufosinate in this management system and showed promising results for saflufenacil/imazethapyr.

A utilização de altas doses de glyphosate, mesmo na tecnologia tolerante (RR) pode causar injúrias nas plantas, conhecido como efeito “Yellow flashing”, que é caracterizado por um amarelecimento das folhas apicais, podendo levar à perda de produtividade. O presente estudo objetivou avaliar técnicas visando a atenuação do efeito de doses de glyphosate em cultivares tolerantes de soja (RR e RR2). Os ensaios foram conduzidos em estufa nos anos 2015/2016 e 2016/2017, em Palotina, região oeste do Paraná em um arranjo inteiramente casualizado. O primeiro ensaio foi conduzido em arranjo fatorial 3x8 (produtos x cultivares) com quatro repetições utilizando misturas de glyphosate com regulador de crescimento, um composto de aminoácidos e uma fonte de manganês, e no segundo um esquema fatorial 6x3 (produtos x cultivares) utilizando glyphosate, um regulador de crescimento, uma fonte de manganês isolados e o glyphosate associado aos demais produtos, além de um tratamento controle sem aplicação. Foram avaliados visualmente a fitotoxicidade, índice de clorofila, massa seca de parte aérea e de raiz. Observou-se uma diferença de resposta para as cultivares devido a características de cada genótipo. Não foram observadas diferenças entre os produtos. A cultivar ‘M6210’ apresentou-se maior sintoma de fitointoxicação enquanto a cultivar ‘BMX Ponta’ apresentou maior tolerância. Para o segundo ensaio não foi observado efeito fitotóxico.

The use of high rates of glyphosate, even if tolerant (RR) technology, can cause leaf insults, such as the yellow flashing effect, which is characterized by a yellowing of the leaves, which can lead to loss of yield. The present study aimed to increase doses of glyphosate in tolerant soybean. Tests were conducted in greenhouse 2015/2016 and 2016/2017, in Palotina, western region of Paraná in a completely randomized arrangement. The first assay was conducted in a 3x8 factorial set (products x cultivars) with four replicates mixed with glyphosate with growth regulator, one compound of amino acids and one source of manganese, and in the second a factorial scheme 6x3 (products x cultivars) using glyphosate, a growth regulator, a source of manganese and the glyphosate associated to the other products, besides a control without application. A phytotoxicity, chlorophyll index, shoot dry mass and root mass were evaluated visually. A variation of response to cultivar was observed due to characteristics of each genotype. The differences between the products were not observed. A cultivar ‘M6210’ presented greater symptom of crop injury while cultivating ‘BMX Ponta’, presenting greater tolerance. No phytotoxic effect was observed for the test.