RESUMEN La eficiencia de absorción, translocación y control satisfactorio de malezas pueden ser afectados por el lugar de aplicación del herbicida. Sin embargo, durante la recolección de cultivos previos a la soya, el corte realizado por la cosechadora en la yerba carnicera dificulta el manejo de cultivos en pre-siembra al limitar el área foliar de absorción. Se realizaron experimentos para evaluar la eficiencia del control y el potencial de translocación de saflufenacil en plantas de yerba carnicera en diferentes condiciones. El primer experimento se organizó en esquema factorial 2x10. El factor A corresponde a la integridad de la hoja y el factor B corresponde a los diferentes niveles de daño y aplicación de saflufenacil. El control de Conyza se evaluó a los 7, 14 y 21 días después del tratamiento herbicida (DAT), y el peso seco a los 21 DAT. El experimento II consistió en aplicar saflufenacil a diferentes estructuras de Conyza, donde se evaluó el porcentaje de área necrótica a 1, 3, 5 y 7 DAT. El control de Conyza obtenido fue superior al 75% en todos tratamientos usando saflufenacil, con mayor control en plantas previamente defoliadas. La aplicación de saflufenacil en plantas de 10 y 20 cm fue eficaz en todos los tratamientos. Además, saflufenacil aplicado en el tallo viejo mostró un área necrótica mayor, mientras la aplicación en el sitio del corte generó como resultado un área menos necrótica. La translocación de saflufenacil se da através del xilema y el tallo demostrando ser el elemento a través del cual se da la absorción del herbicida.

ABSTRACT Efficient herbicide absorption and translocation, and satisfactory weed control can be affected by the site of herbicide application. However, during harvesting of crops of previous soybean sowing, the cutting process made by harvesters on the fleabane may generate a difficult management in pre-sowing of the crop by limiting the leaf area of the absorption of the herbicide. Experiments were conducted to evaluate the control efficiency and translocation potential of saflufenacil in fleabane plants with different leaf and stem conditions. Experiment I was arranged in a 2x10 factorial scheme, with factor A corresponding to leaf integrity, and factor B corresponding to different levels of injury and saflufenacil application. Weed control was evaluated at 7, 14, and 21 days after herbicide treatment (DAT), and dry matter was evaluated at 21 DAT. Experiment II consisted of applying saflufenacil to different fleabane structures, where the percentage of necrotic area was evaluated at 1, 3, 5, and 7 DAT. Fleabane control was higher than 75% in all treatments with saflufenacil application, with greater control in plants previously defoliated. Saflufenacil application on 10 and 20 cm hairy fleabane plants was also efficient in all treatments. Saflufenacil application in old stem showed a larger necrotic area, while application in the site of the cutting resulted in a lower necrotic area. The main pathway for translocation of saflufenacil is via xylem and the stem proved to be the absorption element of the herbicide when leaf area is limited.

RESUMO: O objetivo deste trabalho foi avaliar a interação entre herbicidas associados ao saflufenacil para o controle de capim-arroz e a determinação do efeito dos herbicidas sobre os parâmetros fotossintéticos e de fluorescência de clorofila. O experimento foi conduzido em casa de vegetação em esquema fatorial 2x8, cujo fator A testou os biótipos resistente e suscetível; e o fator B os herbicidas: saflufenacil (70 g i.a. ha-1), clomazone (180 g i.a. ha-1), imazapyr+imazapic (73,5+24,5 g i.a. ha-1), cyhalofop (360 g i.a. ha-1), as associações desses com saflufenacil, e testemunha sem tratamento. Foi avaliado o controle aos 7, 14, 21 e 28 dias após a aplicação dos herbicidas (DAA), massa seca da parte aérea aos 28 DAA, avaliação de parâmetros fotossintéticos com analisador de gás infravermelho (IRGA) e emissão de fluorescência da clorofila a 24 e 48 horas após aplicação dos tratamentos, respectivamente, e interação dos herbicidas. A associação de saflufenacil com herbicidas testados na maior parte não modificou a resposta dos herbicidas para o controle de capim-arroz em ambos os biótipos. O biótipo resistente apresentou menor efeito negativo nos processos de fluorescência de clorofila e parâmetros de fotossíntese na associação de herbicidas com saflufenacil. O herbicida cyhalofop associado ao saflufenacil demonstra ser eficiente para o controle de capim-arroz suscetível e resistente a ALS.

ABSTRACT: The objectives of this research were to evaluate the interaction between herbicides mixed with saflufenacil for the control of barnyardgrass and to determine the effect on photosynthetic and chlorophyll fluorescence parameters. The experiment was conducted in a greenhouse in a 2x8 factorial scheme, whose factor A tested resistant and susceptible biotypes; and factor B the herbicides: saflufenacil (70 g a.i. ha-1), clomazone (180 g a.i. ha-1), imazapyr + imazapic (73.5 + 24.5 g a.i. ha-1), and cyhalofop (360 g a.i. ha-1), the mixtures of these herbicides with saflufenacil, and control without treatment. Weed control was assessed 7, 14, 21 and 28 days after herbicide application (DAA), as well as shoot dry matter at 28 DAA, photosynthetic parameters using infrared gas analyzer (IRGA), and emission of chlorophyll a fluorescence after 24 and 28 hours of application of treatments, respectively, and interaction of herbicides. Combination of saflufenacil with the herbicides tested in general did not change the response of both barnyardgrass biotypes to the herbicides used. The resistant biotype showed a lower negative effect on chlorophyll fluorescence and photosynthesis parameters in the combination of herbicides with saflufenacil. The herbicide cyhalofop was effective for the control of ALS-susceptible and resistant barnyardgrass.