Chemical control of signalgrass for establishing Tanzania-grass

Herbicides have been used to control Brachiaria grass in pastures established or in formation given their practicality, however their efficiency is questionable due to the lack of specific graminicides for different forage species. Therefore, the goal of this study was to evaluate the efficiency of glyphosate and fluazifop-p-butyl in the control of Brachiaria decumbens (signalgrass) and the intoxication levels of Panicum maximum cv. Tanzania (Tanzania quinea grass) in pasture establishment. The experiments were designed in randomized blocks, in a 2 × 5 × 4 factorial arrangement of two herbicides (fluazifop-p-butyl and glyphosate), five doses equivalent to the commercial dosage of each herbicide (0.25; 0.50; 1.00; 1.50; 200), and four evaluation times after herbicide application (15, 21, 30 and 45 days). There was interaction between doses and evaluation times. The dose 1.5 L ha-1 fluazifop-p-butyl provides efficient control of signalgrass, however, leads to high intoxication in Tanzania guinea grass. Glyphosate is efficient in the control of signalgrass even at the lowest dose (90 g ha-1 ), however, it causes high intoxication in Tanzania guinea grass, preventing its use in developing pastures. It can be concluded that fluazifop-p-butyl and glyphosate herbicides are not recommended for the control of B. decumbens, cv. Basilisk in developing pastures of Tanzania guinea grass.(AU)

Chemical control of signalgrass for establishing Tanzania-grass

Herbicides have been used to control Brachiaria grass in pastures established or in formation given their practicality, however their efficiency is questionable due to the lack of specific graminicides for different forage species. Therefore, the goal of this study was to evaluate the efficiency of glyphosate and fluazifop-p-butyl in the control of Brachiaria decumbens (signalgrass) and the intoxication levels of Panicum maximum cv. Tanzania (Tanzania quinea grass) in pasture establishment. The experiments were designed in randomized blocks, in a 2 × 5 × 4 factorial arrangement of two herbicides (fluazifop-p-butyl and glyphosate), five doses equivalent to the commercial dosage of each herbicide (0.25; 0.50; 1.00; 1.50; 200), and four evaluation times after herbicide application (15, 21, 30 and 45 days). There was interaction between doses and evaluation times. The dose 1.5 L ha-1 fluazifop-p-butyl provides efficient control of signalgrass, however, leads to high intoxication in Tanzania guinea grass. Glyphosate is efficient in the control of signalgrass even at the lowest dose (90 g ha-1 ), however, it causes high intoxication in Tanzania guinea grass, preventing its use in developing pastures. It can be concluded that fluazifop-p-butyl and glyphosate herbicides are not recommended for the control of B. decumbens, cv. Basilisk in developing pastures of Tanzania guinea grass.

Chemical control of signalgrass in alfalfa crops / Controle químico do capim-braquiária em cultivo de alfafa

The use of herbicides to control grass in Medicago sativa (alfalfa) pastures is still incipient. Therefore, the objective of this study was to evaluate the efficiency of fluazifop-p-butyl in the control of Brachiaria decumbens (signalgrass) in alfalfa. Thus, randomized block design was used, with seven doses of fluazifop-p-butyl (0, 25, 50, 100, 200, 300, 400 g ha-1), and four replications. Herbicide application was performed when the plants had about 20 cm height. Chlorophyll fluorescence, control of signalgrass and alfalfa toxicity were evaluated at 7, 15 e 30 days after application (DAA) and, at 45 DAA and 45 days after cut (DAC), both species were cut and tiller density, as well as branches and dry matter of forage species, were determined. Fluazifop-p-butyl does not affect the integrity of the photosynthetic apparatus of alfalfa plants, due to high tolerance to this mechanism of action presented by dicotyledonous species. However, signalgrass had physiological variables negatively affected by the herbicide, indicating the presence of physiological stress, even at the lowest doses of the product. The dose of 50 g ha-1 of fluazifop-p-butyl is effective in controlling signalgrass, without causing physiological and growth damage in alfalfa plants.(AU)

O uso de herbicidas no controle de gramíneas em pastagens de Medicago sativa (alfafa) ainda é incipiente, desse modo objetivou-se avaliar a eficiência do fluazifop-p-butil no controle de Brachiaria decumbens (capim-braquiária) em alfafa. Para tal utilizou-se o delineamento em blocos casualisados, com sete doses de fluazifop-p-butil (0, 25, 50, 100, 200, 300, 400 g ha-1), e quatro repetições. A aplicação do herbicida foi realizada quando as plantas apresentavam cerca de 20 cm de altura. Foram realizadas avaliações de fluorescência da clorofila, controle do capim-braquiária e intoxicação da alfafa aos 7, 15 e 30 dias após aplicação (DAA) e aos 45 DAA e 45 dias após o corte (DAC) ambas as espécies foram cortadas e determinadas a densidade de perfilhos e ramificações e a massa seca das espécies forrageiras. O fluazifop-p-butil não afeta a integridade do aparato fotossintético de plantas da alfafa, devido à grande tolerância a esse mecanismo de ação apresentado por espécies dicotiledôneas. O capim-braquiária teve as variáveis fisiológicas afetadas negativamente pelo herbicida, indicando a presença de estresse fisiológico, mesmo nas menores doses do produto. A dose de 50 g ha-1 de fluazifop-p-butil é eficiente no controle de capim-braquiária, sem causar danos fisiológicos e no crescimento de plantas de alfafa.(AU)

Chemical control of signalgrass in alfalfa crops / Controle químico do capim-braquiária em cultivo de alfafa

The use of herbicides to control grass in Medicago sativa (alfalfa) pastures is still incipient. Therefore, the objective of this study was to evaluate the efficiency of fluazifop-p-butyl in the control of Brachiaria decumbens (signalgrass) in alfalfa. Thus, randomized block design was used, with seven doses of fluazifop-p-butyl (0, 25, 50, 100, 200, 300, 400 g ha-1), and four replications. Herbicide application was performed when the plants had about 20 cm height. Chlorophyll fluorescence, control of signalgrass and alfalfa toxicity were evaluated at 7, 15 e 30 days after application (DAA) and, at 45 DAA and 45 days after cut (DAC), both species were cut and tiller density, as well as branches and dry matter of forage species, were determined. Fluazifop-p-butyl does not affect the integrity of the photosynthetic apparatus of alfalfa plants, due to high tolerance to this mechanism of action presented by dicotyledonous species. However, signalgrass had physiological variables negatively affected by the herbicide, indicating the presence of physiological stress, even at the lowest doses of the product. The dose of 50 g ha-1 of fluazifop-p-butyl is effective in controlling signalgrass, without causing physiological and growth damage in alfalfa plants.

O uso de herbicidas no controle de gramíneas em pastagens de Medicago sativa (alfafa) ainda é incipiente, desse modo objetivou-se avaliar a eficiência do fluazifop-p-butil no controle de Brachiaria decumbens (capim-braquiária) em alfafa. Para tal utilizou-se o delineamento em blocos casualisados, com sete doses de fluazifop-p-butil (0, 25, 50, 100, 200, 300, 400 g ha-1), e quatro repetições. A aplicação do herbicida foi realizada quando as plantas apresentavam cerca de 20 cm de altura. Foram realizadas avaliações de fluorescência da clorofila, controle do capim-braquiária e intoxicação da alfafa aos 7, 15 e 30 dias após aplicação (DAA) e aos 45 DAA e 45 dias após o corte (DAC) ambas as espécies foram cortadas e determinadas a densidade de perfilhos e ramificações e a massa seca das espécies forrageiras. O fluazifop-p-butil não afeta a integridade do aparato fotossintético de plantas da alfafa, devido à grande tolerância a esse mecanismo de ação apresentado por espécies dicotiledôneas. O capim-braquiária teve as variáveis fisiológicas afetadas negativamente pelo herbicida, indicando a presença de estresse fisiológico, mesmo nas menores doses do produto. A dose de 50 g ha-1 de fluazifop-p-butil é eficiente no controle de capim-braquiária, sem causar danos fisiológicos e no crescimento de plantas de alfafa.