Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaf 69). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 44-48). Also available via the Internet.

Thesis (D.Sc.(Agric.))(Plant Production)--University of Pretoria, 1990. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

No description available.

The influence of environment on efficacy of postemergence herbicides was quantified. A three-fold approach included: first, use of field test sites to select an herbicide sensitive to environmental conditions; second, quantify herbicide responses to temperature, moisture, and morphological conditions; and third, conduct laboratory research to determine if differential uptake, translocation, or metabolism would account for these responses to the environment. Section one of the research was designed to determine if field research can be used to detect herbicides sensitive to environmental influences. Herbicides compared were: imazaquin, BAS 514 and tridiphane to fenoxaprop-ethyl (the cool-season herbicide standard) for postemergence control of large crabgrass (Digitaria sanguinalis) in Kentucky bluegrass (Poa pratensis) and bermudagrass (Cynodon dactylon) turf. BAS 514 was significantly influenced by variable environment. Section two of the research studied control of southern crabgrass (Digitaria ciliaris) by BAS 514 as influenced by morphological and physiological factors. BAS 514 efficacy was influenced by crabgrass growth stage, air temperature, and irrigation level. Flowering crabgrass plants were the most tolerant, while preemergence and true-leaf stages were the most sensitive. Plants held at soil moisture levels near saturation and 25° C were the most sensitive to BAS 514. BAS 514 was not effective against plants grown at low moisture levels and 15° or 35° C. Section three of the research compared the uptake, distribution, and metabolism of ¹⁴C BAS 514 in southern crabgrass and Kentucky bluegrass plants, a sensitive and non-sensitive species. Foliar applied BAS 514 was rapidly absorbed by both species. Uptake and partitioning was similar in both species from 0.5 to 32 h, but different at 128 h, with bluegrass more uniformly distributing the herbicide. Metabolism of BAS 514 was low with only 3% metabolism in both species. Uptake, distribution, and metabolism apparently are not involved in differential sensitivity to BAS 514. Field research can be used to select an herbicide sensitive to environmental influences. Temperature and soil moisture influenced the herbicidal activity of BAS 514. Uptake, translocation and metabolism did not appear to influence selectivity of this herbicide. / Ph. D.

Orientador: Robinson Antonio Pitelli / Banca: Ricardo Victória Filho / Banca: Roberto Estevão Bragion de Toledo / Resumo: O capim-colchão possui ampla colonização e distribuição geográfica, apresentando crescimento vigoroso mesmo em condições de estiagem e sua eficácia de controle não tem sido consistente, especialmente com herbicidas inibidores do Fotossistema II. As razões desta falta de consistência de controle são muitas, no entanto a existência de diferentes espécies pode ser considerada uma das principais. Tendo por base os relatos acima, o presente trabalho teve por objetivo identificar as diferentes espécies do complexo Digitaria spp e avaliar as respostas a ação de diferentes herbicidas inibidores de fotossíntese e associação com inibidores de carotenóides em estudos de curvas de dose resposta. Os herbicidas foram aplicados em pré-emergência com quatro repetições avaliando o controle até 60 DAA. Nos resultados obtidos, pode-se observar que existe diversidade de espécies dentro do gênero Digitaria em áreas cultivadas com cana-de-açúcar. Apenas nestes estudos foram identificadas D. horizontalis, D. nuda e D. ciliaris, as quais mostraram diferença na susceptibilidade aos herbicidas testados. Também foram verificadas diferenças entre os acessos dentro das espécies D. horizontalis e D. nuda. O fato de todas as plantas serem designadas com o nome popular de capim-colchão, estudos de controle, muitas vezes, podem mudar em função da espécie, gerando divergências na eficácias biológicas dos herbicidas sobre este complexo de espécies, pois não são incomuns em que as duas ou mais ocorram na mesma área / Abstract: The crabgrass has extensive colonization and geographical distribution, with strong growth even in drought conditions and the control performance has not been consistent, especially with Photosystem II inhibiting herbicides. The reasons for this lack of control consistenc are many, but the existence of different species can be considered a major. Based on the above reports, this aimed study to identify the different species of the Digitaria spp complex and evaluate responses to the action of several photosystem - II inhibiting herbicides in studies of dose-response curves. This study was conducted evaluating the performance of six bouts of crabgrass in the sugarcane in São Paulo State to herbicides: ametryn, diuron; ametryn + clomazone, diuron + hexazinone, diuron + hexazinone + mesotrione; hexazinone; metribuzim and tebuthiuron. Herbicides were applied in pre-emergence with four replications evaluating the control until 60 DAA. The results obtained, it can be seen that there really is diversity of species within the genus Digitaria in areas cultivated with sugarcane. Only in these studies were identified D. horizontalis, D. nuda and D. ciliares, which showed differences in susceptibility to herbicides. There were also significant differences among accessions within species D. horizontalis and D. nuda. The fact that all plants are designed with the popular name of crabgrass, the results of studies of chemical control, can often change depending on the species, leading to differences in biological effectiveness of herbicides on this species complex, as there are unusual in that two or more of them occur in the same area / Mestre

Mesotrione is under evaluation for registration in turfgrass for weed control, but often requires repeat treatments. Previous research in agricultural crops indicates tank mixtures with mesotrione may improve weed control. Three field trials were conducted in 2005 and 2006 in Blacksburg, VA on smooth crabgrass in perennial ryegrass and tall fescue. Data indicate mesotrione applied in combination with bentazon, bromoxynil, or carfentrazone, controlled smooth crabgrass better than any of these herbicides applied alone at all sites. Adding mesotrione to MSMA and quinclorac improved smooth crabgrass on of three sites. Sequential mesotrione applications improved long term weed control. / Master of Science

Alpacas have been gaining prominence in the U.S. since the early 1980s. In pastures, dung beetle activity has been shown to enhance the degradation and incorporation of dung into the soil. The benefits of this activity have been quantified for cattle, but not for alpacas. The objectives of this study were to document the dung beetle species present in alpaca pastures, and to evaluate the impact of dung beetle activity on the growth of a common summer annual grass. In 2010 and 2011, dung beetle species present in alpaca pastures located at Virginia State University (VSU), were evaluated weekly from late May until late August. Eleven species of dung beetles were found, with Onthophagus taurus Schreber being the most dominant. In 2011, a greenhouse study was conducted at Virginia Tech's Southern Piedmont Research Station. Treatments included a control (no dung, no beetles), dung only, dung with five pairs of O. taurus, and dung that was allowed to be colonized in alpaca pastures at VSU. The addition of O. taurus and the field colonization both significantly increased total yield over the no dung control by 10% and 14%, respectively. These results indicate that healthy and diverse dung beetle communities occur in alpaca pastures in the mid-Atlantic region, and that the presence of these beetles would likely enhance nutrient cycling and pasture growth. However, it is important to remember that dung beetles are just one component of many found in a healthy grassland ecosystem, and the functions of these components are interrelated. / Master of Science

Ustilsgo syntherismae (Schwein.) Peck, which causes loose smut of crabgrass, infects its host systemically and destroys seed production. Greenhouse experiments were carried out to investigate the mode of infection, the disease incidence that can be obtained by artificial inoculation and the conditions necessary for optimum infection, cross-infection on southern and smooth crabgrass, and the reasons for the late observance of the disease. U. syntherismse infected southern crabgrass, Digitaria ciliaris (Retz.) Koeler, by both seed-borne and soil-borne teliospore inoculum. Disease incidence was high (84-91%) in some treatments. Higher rates of teliospore application resulted in larger percentages of smutted plants. When infesting the potting mixture, the highest percentages of smutted plants were obtained when infestation and planting were done at the same time. Earlier or later planting resulted in fewer smutted plants. When planting at various depths, greater numbers of smutted plants were obtained when inoculated seed were planted 0.5 to 1.0 cm below the surface versus planting on the surface or at greater depths. The appearance of 50% of infected plants' first panicles (in greenhouse experiments) was delayed by 4.5 weeks compared to the emergence (50%) of first panicles from healthy plants. In cross inoculation experiments, southern and smooth crabgrass plants developed smut only when inoculated with spores collected from large and smooth crabgrass~ respectively. / Master of Science

Made available in DSpace on 2014-06-11T19:28:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-05Bitstream added on 2014-06-13T20:18:13Z : No. of bitstreams: 1 lucio_fr_me_jabo.pdf: 360282 bytes, checksum: 77f31007525ac85b5cdfcbdf88363eab (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Monsanto / O capim-colchão possui ampla colonização e distribuição geográfica, apresentando crescimento vigoroso mesmo em condições de estiagem e sua eficácia de controle não tem sido consistente, especialmente com herbicidas inibidores do Fotossistema II. As razões desta falta de consistência de controle são muitas, no entanto a existência de diferentes espécies pode ser considerada uma das principais. Tendo por base os relatos acima, o presente trabalho teve por objetivo identificar as diferentes espécies do complexo Digitaria spp e avaliar as respostas a ação de diferentes herbicidas inibidores de fotossíntese e associação com inibidores de carotenóides em estudos de curvas de dose resposta. Os herbicidas foram aplicados em pré-emergência com quatro repetições avaliando o controle até 60 DAA. Nos resultados obtidos, pode-se observar que existe diversidade de espécies dentro do gênero Digitaria em áreas cultivadas com cana-de-açúcar. Apenas nestes estudos foram identificadas D. horizontalis, D. nuda e D. ciliaris, as quais mostraram diferença na susceptibilidade aos herbicidas testados. Também foram verificadas diferenças entre os acessos dentro das espécies D. horizontalis e D. nuda. O fato de todas as plantas serem designadas com o nome popular de capim-colchão, estudos de controle, muitas vezes, podem mudar em função da espécie, gerando divergências na eficácias biológicas dos herbicidas sobre este complexo de espécies, pois não são incomuns em que as duas ou mais ocorram na mesma área / The crabgrass has extensive colonization and geographical distribution, with strong growth even in drought conditions and the control performance has not been consistent, especially with Photosystem II inhibiting herbicides. The reasons for this lack of control consistenc are many, but the existence of different species can be considered a major. Based on the above reports, this aimed study to identify the different species of the Digitaria spp complex and evaluate responses to the action of several photosystem – II inhibiting herbicides in studies of dose-response curves. This study was conducted evaluating the performance of six bouts of crabgrass in the sugarcane in São Paulo State to herbicides: ametryn, diuron; ametryn + clomazone, diuron + hexazinone, diuron + hexazinone + mesotrione; hexazinone; metribuzim and tebuthiuron. Herbicides were applied in pre-emergence with four replications evaluating the control until 60 DAA. The results obtained, it can be seen that there really is diversity of species within the genus Digitaria in areas cultivated with sugarcane. Only in these studies were identified D. horizontalis, D. nuda and D. ciliares, which showed differences in susceptibility to herbicides. There were also significant differences among accessions within species D. horizontalis and D. nuda. The fact that all plants are designed with the popular name of crabgrass, the results of studies of chemical control, can often change depending on the species, leading to differences in biological effectiveness of herbicides on this species complex, as there are unusual in that two or more of them occur in the same area