908 resultados para Herbicidas - Toxicologia


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Under conservation tillage systems is critical to maintaining plant residues from previous crops on the soil surface. A technique called Hormesis aims to increase the amount of straw and also cause a delay in straw decomposition. Therefore, this study aimed to evaluate the agronomic characteristics of corn under no-tillage system subjected to Hormesis. The experiment was carried out at UNESP campus in the city of Botucatu, SP . The experimental was design in completely randomized blocks. The treatments based on the technique of Hormesis were : control (no application) , sub Gliphosate low dosage (12.5 g.ai.ha - 1 ) , sub Gliphosate average dosage (25 g. ai.ha - 1 ) , sub Gliphosate high dose (50 g. ai.ha -1 ), 2,4-D under low dose (100 g. ai.ha -1 ), 2,4-D sub average dosage (200 g. ai.ha -1 ) 2,4- D under high dosage (300 g. ai.ha -1 ) sub Verdict low dose (0.625 g. ai.ha -1 ) sub Verdict average dosage (1.25 g. ai.ha -1 ) , sub Verdict high dosage (2.5 g. ai.ha - 1 ) . In addition, the following characteristics were evaluated: plant height, first ear growth, stem diameter , ear length , number of rows per cob, cob diameter , , percentage of grains on the cob , mass of plant dry matter, and yield. The results showed that all the treatments showed no statistical difference, the maize was not affected with sub doses of herbicides applications under the field and weather conditions in which the experiment was conducted.

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The objective was to evaluate the influence of intervals without rain after the application of mixtures of carfentrazone-ethyl and glyphosate in the effectiveness of control on Commelina benghalensis. The experimental design was completely randomized with 11 treatments, with two rates of the mixture carfentrazone + glyphosate, 30 + 960 (with sequential application at 21 DAA of the mixture 20 + 960 g ha-1) and 50 + 960 g ha-1 of a.i. and five intervals of precipitation 0, 3, 6, 12 and 24 hours after application (HAA), with four repetitions, being an absolute check. The mixture was applied in post-emergence, then was carried out simulations of rain in the predetermined intervals. Were assessed the effectiveness of visual control (0 to 100 %) at 7, 14, 21, 28, 35 and 42 DAA. The results were compared by t test, with 10 % level of probability. It was observed that the application of the herbicides carfentrazone + glyphosate in the evaluated rates and even in the sequential application did not have control of C. benghalensis. The results with the second application are greater than the single application, and the best absorption of the mixture carfentrazone + glyphosate by C. benghalensis when there is a bigger interval between application and rainfall occurrence, and is necessary a minimum interval of 6 HAA for intermediate control of C. benghalensis.

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The aim of this study was to correlate the chemical control efficacy in post-emergence of Brachiaria decumbens Stapf. (signal grass) and Brachiaria plantaginea Hitchc. (alexandergrass) through ACCase-inhibitor enzyme herbicide application in function of the stage of development of the plant in order to contribute to the chemical management of these weed species. B. decumbens and B. plantaginea were sown in plastic pots filled with soil and kept in a greenhouse. For chemical control evaluation, the following herbicides were tested (g ha-1): fluazifop-p-butyl at 150, haloxyfop-methyl at 50, and sethoxydim at 230. The herbicides were applied in all three plant development phases: stage 1 (plants presenting 4-6 leaves at 15 days after emergence), stage 2 (plants presenting 3-4 tillers at 23 days after emergence), and stage 3 (adult plants in the beginning of flowering at 48 days after emergence). Evaluations were done at 4, 7, 10, 14, 17, 21, 24, and 28 days after herbicide application. The developmental stage of the two Brachiaria species was instrumental in the efficiency of the control provided by different herbicides. Sethoxydim was the most efficient herbicide in controlling Brachiaria species in the three evaluated development stages.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The aim of this study was to evaluate the efficacy of glyphosate and 2,4-D alone and in combination, in the control of Commelina villosa. We studied two methodologies for evaluating herbicide absorption in eight time intervals for washing (simulating rainfall after application) and cutting of leaves (simulating abortion as a defense strategy): 2, 4, 6, 8, 12, 24 and 48 hours after herbicide application, and a treatment without washing or cutting the leaves in a completely randomized design with four replications in a 3 x 7 + 1 factorial design (three herbicides x seven periods – hours after application). Herbicides and doses tested were: glyphosate (1,440 g ha-1), 2,4-D (720 g ha-1) and a mixture of glyphosate + 2,4-D (1,080 + 720 g ha-1). The simulation of rain interfered negatively in the plant control with glyphosate. The control with the herbicide 2,4-D was affected only for the period of 2 hours. Periods of rain simulation did not influence the control of plants with a mixture of glyphosate + 2,4-D. For the study with the cutting of treated leaves, all treatments regardless of the period of cutting the leaves were influenced negatively in terms of plant control, the plants showing regrowth when treated with 2,4-D alone.

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Marchantia polymorpha develops under environmental conditions of high relative humidity and shading. As this habitat is the usually used in nurseries for the growth of seedlings of native tree species that species grows very quickly among developing tree seedlings and causes severe losses. This study was undertaken viewing more efficient either physical or chemical methods for the control of M. polymorpha. Two experiments were conducted under greenhouse conditions. In the first acetic acid (10, 20, and 40% of concentration), oxygenated water (50 and 100%) and the herbicides glyphosate (1,680 g AI ha) and fomesafen (375 g AI ha-1 ) were applied to the seedlings. In the second, the treatments consisted of soil previously submitted to a temperature of 105 °C for 48 hours, soil submitted to solarization in black plastic and in transparent plastic bags for 30 days, preemergence application of diuron (1,750 g AI ha-1 ) and trifluralina (1,575 g AI ha-1 ). The visual evaluations of the methods were performed 7, 14, 21, and 28 days after the application (DAA) and at 60 and 120 DAA, respectively, for the first and the second experiment. Only diuron and trifluralina resulted in a 100% control of M. polymorpha 120 DAA.

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Pós-graduação em Agronomia (Produção Vegetal) - FCAV

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The action of man has led, over the years, major impacts on the environment, especially in aquatic ecosystems, leading to an impairment of water quality, considered one of the essential factors for the maintenance of vital functions and consequently the life of the planet. Among the activities considered a risk for the environment are linked to pollution from many sources and even entire watersheds, whether by industrial waste, sewage, or for substances used in agriculture, such as pesticides, herbicides and fertilizers. The (2,4-D) 2,4- dichlorophenoxyacetic acid is used worldwide, and the fact that its genotoxicity is proven by several studies and by its long persistence in soil, which enables the leaching and percolation of compounds affecting water bodies, toxicity studies are relevant and justifiable. Thus, this study aimed to evaluate the toxicity of 2,4-D by examining the liver of the fish Oreochromis niloticus exposed to different dilutions. Portions of liver were collected and fixed for histological and histochemical techniques to detect total proteins, polysaccharides and lipids. lipids. Treatment with 2,4-D herbicide apparently did not alter the lipid profiles, the accumulation of polysaccharides, and the presence of total proteins. The 2.5 and 5.0% were lethal to fish. These mortalities are probably of high toxic and cytotoxic potential of 2,4-D herbicide results. Several histopathological changes were found, such as: loss of cytoplasmic integrity, loss of cell limit, nuclear deformation, vacuolated cytoplasm, tissue disorganization and hydropic degeneration. Statistically significant changes were: hydropic degeneration and vacuolated cytoplasm. It is concluded, therefore, that the qualitative morphological analysis is an important method for observing changes in liver toxicology studies. As the O. niloticus species is an efficient biological indicator of water pollution by 2,4-D

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)