Made available in DSpace on 2014-08-20T14:07:35Z (GMT). No. of bitstreams: 1 dissertacao_diego_severo_fraga.pdf: 981696 bytes, checksum: 8402f7a17f38638a74dfdc1e8398594d (MD5) Previous issue date: 2012-03-02 / Ryegrass is an annual cycle weed, found in virtually all winter crops, orchards and vineyards of Southern Brazil. The species is usually controlled by glyphosate, however, continued use of the product selected resistant biotypes. The managing with acetyl Coenzime A carboxylase (ACCase) enzyme inhibiting herbicides is the main alternative to control these species, which has not been satisfactory in some places, causing suspicion of being selected biotypes that are resistant to this herbicide group. The objective of this research was to evaluate the distribution of ryegrass biotypes resistant to ACCase enzyme inhibitors herbicides in Rio Grande do Sul (RS); assess by means of dose-response curves ryegrass biotypes resistant and susceptible to the herbicide fluazifop; estimate the fitness cost of susceptible and resistant biotype to fluazifop, and to investigate the competitive ability of these biotypes among themselves and with the wheat crop. Thus, seeds of ryegrass plants that survived applications of ACCase enzyme inhibitors were collected from farms in Northern RS, comprising 80 towns. The results showed that there were ryegrass resistant biotypes to the herbicide fluazifop when applied at the maximum dose of 125g a.i.ha-1 and stage specified by the manufacturer. Ryegrass biotypes have different levels of herbicide resistance, and the biotype of ryegrass TUC 11 has low-level resistance to the herbicide fluazifop. In the assessment of competitive ability and fitness cost it was found that the susceptible ryegrass and low level resistance, in general, have similar values for these variables. Wheat cultivar FUNDACEP Horizonte, in general, showed greater competitive ability than the low level resistance biotype and equivalent to the susceptible. / O azevém é uma planta daninha de ciclo anual, encontrada em praticamente todas as lavouras de inverno, em pomares e vinhedos da região Sul do Brasil. A espécie é normalmente controlada pelo herbicida glyphosate, no entanto, o uso continuado desse produto selecionou biótipos resistentes. O manejo com herbicidas inibidores da enzima acetil Coenzima A carboxilase (ACCase) é a principal alternativa para o controle dessas espécies, o qual não tem sido satisfatório em alguns locais, provocando a suspeita de que estejam sendo selecionados biótipos resistentes a este grupo de herbicidas. Assim, o objetivo da pesquisa foi avaliar a distribuição dos biótipos de azevém resistentes aos herbicidas inibidores da enzima ACCase no Rio Grande do Sul (RS); avaliar, por meio de curvas de dose-resposta, biótipos de azevém resistente e suscetível ao herbicida fluazifop; estimar o valor adaptativo de biótipo suscetível e resistente ao fluazifop; e, investigar a habilidade competitiva desses biótipos entre si e com a cultura do trigo. Para isso, sementes de plantas de azevém que sobreviveram a aplicações de inibidores da enzima ACCase foram coletadas em lavouras na região norte do RS, totalizando 80 municípios. Os resultados demonstraram que existem biótipos de azevém resistentes ao herbicida fluazifop quando aplicado na dose máxima de 125g i.a.ha-1 e estádio indicado pelo fabricante. Os biótipos de azevém apresentam diferentes níveis de resistência ao herbicida, sendo que o biótipo de azevém TUC 11 apresenta resistência de nível baixo ao herbicida fluazifop. Na avaliação de habilidade competitiva e valor adaptativo verificou-se que os biótipos de azevém suscetível e com resistência de nível baixo, em geral, apresentam valores similares para estas variáveis. A cultura do trigo, cultivar FUNDACEP Horizonte, em geral, apresentou maior habilidade competitiva que o biótipo com nível baixo de resistência e equivalente ao suscetível.

In the fall of 2011, a study was initiated at the Western Kentucky University Farm in Bowling Green, Kentucky on a Crider silt loam (Typic Paleudalf). The objective of this study was to determine cultivar, mowing height, and herbicide effects on bermudagrass, Cynodon dactylon [L.] Pers., suppression in tall fescue, Schedonorus arundinaceus [Schreb.] Dumort., nom. cons. The experimental design was a split plot design with whole plots consisting of varying mowing heights and split plots consisting of different herbicide treatments with three replications. Two separate experiments were conducted. The tall fescue variety ‘KY 31’ was utilized for one study and the turf type cultivar ‘Bullseye’ was utilized in the other. In the fall of 2011, glyphosate (Roundup Pro) was applied to selected plots at the rate of 0.36 kg ae/ha. ‘KY 31’ and ‘Bullseye’ tall fescues were sown into an existing mixed stand of common and hybrid bermudagrass at 342 kg pls/ha. Mowing heights were maintained at 7.62 cm, 10.16 cm, and 12.70 cm. In the spring of 2012, treatments containing fenoxaprop (Acclaim Extra), mesotrione (Tenacity), and fluazifop (Fusilade II) were applied to selected plots at the rates of 0.07 kg ai/ha, 0.48 kg ai/ha, and 0.24 kg ai/ha respectively. A non-ionic surfactant at 0.25% (v/v) was utilized in treatments containing mesotrione and fluazifop. Three weeks later these treatments were applied a second time. Data were collected visually on turf quality, tall fescue cover, broadleaf weed cover, and bermudagrass cover. The study was repeated in 2012 – 2013. Fluazifop and glyphosate + fluazifop resulted in significantly lower turf quality than all other treatments up until ten weeks after initial treatment. Treatments containing fluazifop significantly reduced tall fescue cover but also significantly suppressed bermudagrass cover the greatest. However, these treatments also resulted in the greatest amount of broadleaf weed cover. High mowing heights may play a role in achieving high turf quality ratings and better broadleaf weed and bermudagrass suppression in forage type tall fescue than in turf type tall fescue.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-06-23T11:53:56Z No. of bitstreams: 1 texto completo.pdf: 439400 bytes, checksum: bdb2f56918fe165df7cddb4d2776eeed (MD5) / Made available in DSpace on 2017-06-23T11:53:56Z (GMT). No. of bitstreams: 1 texto completo.pdf: 439400 bytes, checksum: bdb2f56918fe165df7cddb4d2776eeed (MD5) Previous issue date: 2005-10-21 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / A demanda por informações sobre o impacto causado por herbicidas de médio efeito residual no solo motivou o estudo de indicadores microbiológicos que possibilitassem medir o distúrbio provocado à microbiota do solo após a aplicação desses produtos para o controle de plantas daninhas, dando ênfase à cultura do feijoeiro. Dessa forma, foram conduzidos três experimentos com o objetivo geral de verificar o impacto provocado pelos herbicidas fomesafen e fluazifop-p-butil, isolados ou em mistura pré-formulada, largamente utilizados no manejo das plantas daninhas na cultura do feijoeiro, sobre a atividade dos microrganismos do solo. No primeiro experimento, realizado em campo, ao longo do cultivo do feijoeiro, em dois sistemas de plantio – convencional (SPC) e direto (SPD) – avaliaram-se, após a aplicação dos herbicidas mencionados, a respiração basal da microbiota do solo, o carbono da biomassa microbiana (CBM), o quociente microbiano (qMIC), o quociente metabólico (qCO2), a porcentagem de colonização de raízes do feijoeiro por fungos micorrízicos e, ao final do ciclo, o rendimento de grãos. No segundo experimento, a partir de amostras de solo representando SPC e SPD, verificou-se, em laboratório, o efeito da adição de diferentes concentrações dos mesmos herbicidas, isolados e em mistura pré-formulada, sobre a respiração basal da microbiota do solo, CBM e qCO2. No último experimento, avaliou-se o crescimento das estirpes de Rhizobium tropici BR 322 e BR 520, utilizadas como inoculantes na cultura do feijoeiro no Brasil, em meio de cultura, adicionado dos principais herbicidas utilizados ao longo do ciclo do feijoeiro (bentazon, s-metolachlor, imazamox e paraquat, além do fluazifop-p-butil e do fomesafen). De maneira geral, os indicadores microbiológicos avaliados ao longo do ciclo do feijoeiro se mostraram sensíveis à ação dos diferentes herbicidas testados, além de demonstrarem o menor impacto negativo do SPD sobre a microbiota do solo em comparação ao SPC. O qCO2 que estima a eficiência da microbiota do solo em utilizar o carbono da matéria orgânica, evidenciou que a aplicação dos herbicidas testados causou maior impacto negativo quando sobre o solo do SPC. Com o aumento da concentração do fomesafen, observou-se diminuição da microbiota do solo, sendo mais prejudicial na mistura comercial. A partir dos resultados da tolerância das estirpes de rizóbio aos herbicidas, verificou-se que o paraquat promoveu maior inibição do crescimento, seguido pelo fomesafen. Entre as estirpes, BR 520 apresentou maior tolerância à maioria dos herbicidas testados. / The search for information about the impact caused by herbicide on soil motivated the study of microbiological indicators that could measure the harm caused to soil microbiota after the application of products to control weeds, mainly in the common bean crop. Thus, three experiments were conducted in order to verify the impact caused by fomesafen and fluazifop-p-butyl herbicide, isolated or in a commercial mixture on soil microbial activity. The first experiment was conducted under no-till (NTS) and conventional-till (CTS) systems. After herbicide application, the soil was evaluated measuring basal respiration of soil microbiota, microbial biomass carbon (MBC), microbial quotient (qMIC), metabolic quotient (qCO2), root colonization by mycorrhizal fungi and grain yield at the end of the cycle. In the second experiment, conducted in the laboratory, the effect of adding different concentrations of the same herbicide on basal respiration of soil microbiota, MBC and qCO2 was evaluated. The growth of Rhizobium tropici BR 322 and BR 520 was evaluated in the last experiment, by adding the herbicides (bentazon, metolachlor, imazamox and paraquat, plus the fluazifop-p-butil and fomesafen). Microbiological indicators were sensitive to the tested herbicides, besides showing the efficiency of NTS in comparison to CTS. The qCO2 showed that herbicide application caused higher negative impact in CTS. With increasing fomesafen concentrations, soil microbiota decreased, being in commercial mixture, paraquat provided higher growth inhibition, followed by fomesafen. The Rhizobium tropici strains BR 520 showed higher tolerance to most of tested herbicides.

No description available.

A series of experiments was carried out on cultivated oat (Avena sativa L. cv Amuri) to examine the efficacies of fluazifop-butyl and glyphosate against water stressed plants, plants grown in low and high nitrogen and plants treated with gibberellic acid (GA₃). Avena sativa L. was used as a test plant and on completion of the experiments, further studies were carried out on the weed species wild oat (Avena fatua L.). In the laboratory, plants maintained at wilting point for five days before and nine days after spraying and treated with fluazifop-butyl (0.5 kg a.i./ha) appeared healthy 32 days after herbicide application, while plants supplied with water throughout the experiment were completely chlorotic/necrotic and had main stem detachment from within the leaf sheaths. In the field, plants maintained unirrigated until 14 days after spraying with fluazifop-butyl (0.25 kg a.i./ha) or glyphosate (0.18 kg a.i./ha) showed greater tolerance to the herbicides than plants irrigated regularly. Values for seed head yield for water stressed and irrigated plants, 45 days after applying fluazifop-butyl, were 66 g and zero g dryweight/m² respectively. Comparable values for glyphosate treated plants were 65 g and 25 g dryweight/m². Radiolabel studies indicated that in comparision with well watered plants, water stressed plants absorbed 20% less applied ¹⁴C-glyphosate. In addition, the proportion of absorbed ¹⁴C-glyphosate translocated from the treated leaf was 15% less under water stress conditions. Uptake of ¹⁴C-fluazifop-butyl was similar under well watered and water stress conditions and was 30-40% of that applied. The proportion of absorbed ¹⁴C-activity which was transported was very low, but was greater under well watered conditions (7.6%) than under water stress conditions (4.4%). Under well watered conditions in the laboratory and field, fluazifop-butyl (0.25 kg a.i./ha) and glyphosate (0.18 kg a.i./ha) were less toxic at low nitrogen than high nitrogen. For example, 34 days after spraying with fluazifop-butyl under laboratory conditions total plant dry weight was 1.51 g and 0.56 g at 1.0 mol/m³ and 10 mol/m³ applied nitrate respectively. As with soil water content, soil nitrogen content had no effect on uptake of fluazifop-butyl. However, the proportion of absorbed fluazifop-butyl which was translocated out of the treated lamina was greater under high nitrogen conditions (26.1 %) than under low nitrogen conditions (9.3%). Under laboratory conditions, addition of 200 µg GA₃to the leaf sheaths two days prior to spraying with fluazifop-butyl or glyphosate increased the efficacy of both herbicides at low nitrogen. Similarly, under field conditions application of GA₃ (0.21 kg/ha) two days prior to spraying with glyphosate increased the performance of the herbicide against Avena sativa L. growing in a nitrogen depleted soil. At harvest, seed head yield for GA₃ treated and non-treated plants was zero and 7.4 g dry weight/m² respectively. Experiments with Avena latua L. showed that this species was tolerant of fluazifop-butyl and glyphosate when grown in low water or low nitrogen conditions. Under water stress conditions, pre-treatment with GA₃ increased the phytotoxicity of fluazifop-butyl to Avena latua L. Similarily, GA₃ enhanced the phytotoxicity of glyphosate to Avena latua L. grown under low nitrogen conditions. Reduced performance of fluazifop-butyl under stress conditions involves a reduction in translocation of herbicide to meristems, but other factors are likely to be involved. It was concluded that for glyphosate, reductions in uptake and translocation of the herbicide are important factors causing reduced performance of this herbicide under stress conditions. Possible reasons for GA₃ enhancement of fluazifop-butyl and glyphosate activity under stress conditions are discussed and the potential of growth regulators as adjuvants is considered.