Triflxysulfuron is a sulfonylurea herbicide developed for postemergence weed control in cotton, sugarcane, and turf. Greenhouse and laboratory studies were conducted at the Texas A&M University campus and at the USDA-ARS research facility in Stoneville, MS to: 1) quantify the dissipation of trifloxysulfuron in a spray tank at 0, 1, 3, 7, 14, and 21 d after mixing as influenced by pH of the spray carrier and evaluate the resulting effects on efficacy on Palmer amaranth (Amaranthus palmeri S. Wats); 2) determine the effect of spray carrier pH on absorption and translocation of radiolabeled trifloxysulfuron in Palmer amaranth and Texasweed (Caperonia palustris (L.) St. Hil.); 3) determine average edge-of-field concentrations, total mass losses, and fractional losses of trifloxysulfuron applied to cotton at the 5-leaf stage and to bare soil as influenced by simulated rainfall. The dissipation of trifloxysulfuron followed first-order kinetics. Calculated half-life values indicated that hydrolysis occurred more rapidly with the more acidic spray carriers with little or no difference between neutral and alkaline pH levels. Bioassay on Palmer amaranth showed no differences in plant dry weights due to pH level or dissipation time. The absorption of 14C-trifloxysulfuron was greater for Palmer amaranth than for Texasweed when averaged over time and pH. Altering pH did not affect the translocation of trifloxysulfuron in Palmer amaranth. In contrast, translocation of 14C-trifloxysulfuron in Texasweed increased in the order of pH 5 < pH 7 = pH 9. Cumulative trifloxysulfuron losses in runoff from cotton plots were 0.21 g ha-1 while losses from bare plots were 0.13 g ha-1. These values corresponded to fractional losses of 2.7% for cotton plots and 1.7% for bare plots of the total amount applied. These studies provide important information regarding the stability, plant uptake, and runoff potential of a commonly used sulfonylurea herbicide.

Triflxysulfuron is a sulfonylurea herbicide developed for postemergence weed control in cotton, sugarcane, and turf. Greenhouse and laboratory studies were conducted at the Texas A&M University campus and at the USDA-ARS research facility in Stoneville, MS to: 1) quantify the dissipation of trifloxysulfuron in a spray tank at 0, 1, 3, 7, 14, and 21 d after mixing as influenced by pH of the spray carrier and evaluate the resulting effects on efficacy on Palmer amaranth (Amaranthus palmeri S. Wats); 2) determine the effect of spray carrier pH on absorption and translocation of radiolabeled trifloxysulfuron in Palmer amaranth and Texasweed (Caperonia palustris (L.) St. Hil.); 3) determine average edge-of-field concentrations, total mass losses, and fractional losses of trifloxysulfuron applied to cotton at the 5-leaf stage and to bare soil as influenced by simulated rainfall. The dissipation of trifloxysulfuron followed first-order kinetics. Calculated half-life values indicated that hydrolysis occurred more rapidly with the more acidic spray carriers with little or no difference between neutral and alkaline pH levels. Bioassay on Palmer amaranth showed no differences in plant dry weights due to pH level or dissipation time. The absorption of 14C-trifloxysulfuron was greater for Palmer amaranth than for Texasweed when averaged over time and pH. Altering pH did not affect the translocation of trifloxysulfuron in Palmer amaranth. In contrast, translocation of 14C-trifloxysulfuron in Texasweed increased in the order of pH 5 < pH 7 = pH 9. Cumulative trifloxysulfuron losses in runoff from cotton plots were 0.21 g ha-1 while losses from bare plots were 0.13 g ha-1. These values corresponded to fractional losses of 2.7% for cotton plots and 1.7% for bare plots of the total amount applied. These studies provide important information regarding the stability, plant uptake, and runoff potential of a commonly used sulfonylurea herbicide.

Most professional turf in Virginia is comprised of bermudagrass (Cynodon dactylon L.) or (Cynodon dactylon x C. transvaalensis Burtt Davy) as a monoculture in summer and overseeded with perennial ryegrass (Lolium perenne L.) (PR) in winter, during bermudagrass dormancy. Two transitions are required in an overseeding program, fall establishment of PR and spring control of PR. During each transition, turf quality suffers as one grass dies or enters dormancy while another grass is promoted to fill voided areas. Field studies at various locations in Virginia were conducted to investigate methods of improving spring and fall transition. Bermudagrass green cover in August was influenced by duration of PR competition variably between three bermudagrass cultivars. For example, "Midiron", "Patriot", and "Riviera" bermudagrass required 218, 139, and 327 cumulative growing degree days at base 18.3 C (GDD) to reach 95% cover. Bermudagrass biomass was also positively correlated with increasing duration of noncompetitive GDD. Total nonstructural carbohydrates were not correlated to duration of PR competition. Novel application methods were invented and tested at Virginia Tech. Drip, sponge, and strip application methods were used to create patterns of PR control using selective herbicides. Controlling a portion of PR with these methods maintained acceptable turfgrass quality throughout the spring transition and improved bermudagrass cover 12 to 20%, speeding transition by 20 or more days. Efforts to improve PR establishment in dense bermudagrass suggest chemicals that injure existing bermudagrass can improve PR establishment, but cause unacceptable turf discoloration. Mechanical methods to disrupt the bermudagrass canopy had less effect on PR establishment than chemical treatments. / Master of Science

Made available in DSpace on 2015-03-26T13:40:05Z (GMT). No. of bitstreams: 1 texto completo.pdf: 466360 bytes, checksum: e0d21936cd393cfb2e58f6a6e09e5149 (MD5) Previous issue date: 2007-03-16 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective of this work was to evaluate the impact of the herbicides ametryn and trifloxysulfuron-sodium, singly or combined, and 2,4-D, on the soil microrganisms and the mineral nutrition of the sugar-cane plants. In the first trial, it was evaluated the activity of inorganic phosphate-solubilizing microorganisms and the numbers of fungi and bacteria in the rhizosphere of sugar cane and, in the second, the respiratory rate, microbial biomass, metabolic quotient, and total C-CO2 evolved from the soil. In the third trial, the growth and the macro and micronutrients concentrations were evaluated in the foliar tissues of the sugar-cane plants after the herbicide application. In the three trials, foliar tissue samples and rhizospheric and non-rhizospheric soil samples were collected and immediately analyzed at 15, 30, 45, and 60 days after spraying (DAS). At 15 DAS, all herbicides tested led to reductions in the numbers of fungi in the soil. 2,4-D caused a reduction in the densities of bacterial populations in the rhizosphere at all times of evaluation, evidencing a higher sensitivity of bacteria to this compound. The soil microbial biomass was sensitive to ametryn applied singly or combined, especially up to 30 DAS. These treatments resulted in the highest values of metabolic quotient at 45 and 60 DAS. The foliar concentrations of N, P and Mg were not affected for the herbicide use. At 60 DAS, trifloxysulfuron-sodium lead to increase of 22.10% in the biomass accumulation of shoots sugar cane plants. Trifloxysulfuron-sodium and 2,4-D led to higher inorganic phosphate solubilization at 15, 30, and 45 DAS, and 15 and 30 DAS, respectively, without affecting the microbial biomass. This work evidences that herbicide application in the shoots of sugar cane affects the foliar concentrations of macro and micronutrients and the soil microorganisms in the rhizosphere. / Objetivou-se neste trabalho avaliar a microbiota do solo e a nutrição mineral da cana-de-açúcar após aplicação dos herbicidas 2,4-D, ametryn, trifloxysulfuronsodium e ametryn+trifloxysulfuron-sodium. No primeiro ensaio, avaliou-se a atividade e a densidade populacional dos microrganismos solubilizadores de fosfato inorgânico (MSFI) e totais no solo rizosférico da cana-de-açúcar e, no segundo, foram avaliadas a taxa respiratória, a biomassa microbiana e o quociente metabólico do mesmo solo. No terceiro ensaio, avaliaram-se o crescimento e as concentrações de macro e micronutrientes nos tecidos foliares das plantas de cana-de-açúcar após a aplicação dos herbicidas. Nos três ensaios foram realizadas avaliações aos 15, 30, 45 e 60 dias após a aplicação (DAA) dos herbicidas. Todos os herbicidas provocaram redução na densidade populacional fúngica do solo somente no período inicial de avaliação. O 2,4-D foi mais tóxico às bactérias do solo até aos 60 DAA. Analisando o quociente metabólico, ressaltaram-se condições estressantes para a microbiota do solo quando este foi tratado com ametryn isolado e em mistura com trifloxysulfuronsodium. A atividade dos MSFI foi favorecida pela aplicação do 2,4-D até os 30 DAA e o trifloxysulfuron-sodium estimulou essa atividade por todo período de avaliação. As concentrações de N, P e Mg nos tecidos foliares não foram afetados pela utilização dos herbicidas. Em plantas tratadas com trifloxysulfuron-sodium observou-se acréscimo de 22,10% no acúmulo de massa seca da parte aérea das plantas aos 60 DAA. Este trabalho evidenciou que a aplicação dos herbicidas na parte aérea de plantas de cana-de-açúcar afetou a concentração dos nutrientes foliares, a densidade populacional de microrganismos, atividade de solubilização de fosfato, a taxa respiratória, a biomassa e o quociente metabólico na rizosfera.

Cotton (Gossypium hirsutum L.) growth and development, lint yield, and fiber quality are influenced by many management decisions. Three field experiments examining the interaction of plant population and planting date, and cultivar or herbicide and plant growth regulator application on these parameters were conducted in Virginia during 2005 and 2006 and in North Carolina, South Carolina, and Louisiana during specific years. Experiment I: Plant Population and Planting Date Lint yields were highest with populations of 8.9 and 12.8 plants m¯² compared to 5.3 plants m¯² in Virginia and North Carolina, while in Louisiana the highest yields resulted from populations of 5.8 and 9.5 plants m¯² compared to 17.1 plants m¯². Earlier planted (1 May) cotton produced higher yields relative to later planted (21 May) cotton in Louisiana, while yield was not influenced by planting date in Virginia and North Carolina. The impact of plant population and planting date on cotton appeared to be influenced significantly by heat unit accumulation. Experiment II: Cultivar and Mepiquat Pentaborate Application Mepiquat pentaborate (MPB) application consistently decreased plant height, HNR, and enhanced maturity for all cultivars, compared to untreated cotton. A trend of decreasing yield with increasing MPB application in Virginia was observed. These data suggests that cotton response to MPB application is influenced by cultivar maturity or fruiting interval. Experiment III: Trifloxysulfuron-sodium and Mepiquat Chloride Application Trifloxysulfuron-sodium (TFS) did not influence vegetative growth, maturity, or yield in comparison to untreated cotton. Mepiquat chloride (MC) application reduced vegetative growth and enhanced maturity in most years. The results of this experiment demonstrate that TFS application does not have the same effects on plant growth as MC application. / Master of Science