A seleção de biótipos de plantas daninhas resistentes ao herbicida glyphosate no Brasil vem crescendo a cada ano em conseqüência principalmente da dependência dos principais sistemas de produção a este herbicida. Este fenômeno é evidente na citricultura brasileira, onde o glyphosate é o principal herbicida utilizado no controle de plantas daninhas há anos. As infestações da planta daninha conhecida como buva na citricultura é composta da mistura de duas espécies, Conyza canadensis e C. bonariensis, que apresentam ciclo de vida anual ou bianual, e são espécies altamente adaptadas a agroecossistemas com baixo distúrbio mecânico no solo, sendo nos sistemas de produção citrícolas altamente prolíficas. A suspeita de seleção de biótipos de buva resistente ao herbicida glyphosate motivou o desenvolvido desta pesquisa com o objetivo de comprovar a existência de biótipos resistentes, identificar suas principais características de crescimento e estudar alternativas de controle desses biótipos. A comprovação da existência dos biótipos resistentes ao glyphosate foi feita através de curvas dose-resposta, onde se verificou que o nível de resistência (GR50 do biótipo resistente (R) dividido pelo GR50 do biótipo suscetível (S)) está entre 6,15 a 10,79 para os biótipos da espécie Conyza canadensis e entre 1,52 a 14,75 para os biótipos da espécie Conyza bonariensis. Com relação ao estudo de herbicidas alternativos ao glyphosate no seu controle, comparando a aplicação dos herbicidas estudados em plantas de buva sob dois estádios fenológicos, verificou-se que os níveis de controle (%) em plantas com até 10 folhas de desenvolvimento foram de 88, 81,5 e 76,6% respectivamente para os tratamentos com glyphosate + bromacil + diuron (1.440 + 1.200 + 1.200 g ha-1), glyphosate + atrazina (1.440 + 1.500 g ha-1) e glyphosate + diuron (1.440 + 1.500 g ha-1), considerados como mais eficazes; já em plantas em estádio de desenvolvimento reprodutivo, as melhores alternativas de controle foram os tratamentos que continham o herbicida amônio glufosinato 400 g ha-1. O crescimento vegetativo, baseado na biomassa seca de raízes e parte aérea e área foliar, dos biótipos resistentes de ambas as espécies comparados com o seu respectivo biótipo suscetível foi menor que o das plantas resistentes. A umidade demonstrou-se como o principal fator de interferência da germinação de buvas na região de Matão-SP. Dessa maneira, a presente pesquisa comprovou a resistência dos biótipos estudados ao herbicida glyphosate, destacando as diferenças de crescimento entre os biótipos; a eficácia dos herbicidas alternativos de manejo dos biótipos resistentes de buva ao glyphosate é dependente do estádio fenológico de desenvolvimento da planta daninha, sendo o herbicida amônio-glufosinato excelente alternativa de controle do biótipo resistente ao glyphosate. / The selection of weed biotypes resistant to glyphosate in Brazil has been increasing each year, as a consequence of the over reliance of the main cropping systems to this herbicide. This phenomenon is observed in citrus production systems, where glyphosate is the main herbicide used for weed control for several years. The infestation of the weed known as horseweed is composed by the mixture of two species, Conyza canadensis and Conyza bonariensis, that present annual or biannual life cycle, and adaptation to agroecossystems with low mechanical disturbance in the soil, being in the citrus production systems highly prolific. The suspicion of glyphosate resistant biotypes of horseweed motivated the development of this research with the objective of detecting the existence of resistant biotypes, identifying the main characteristics of growth and development and studying alternatives of control of these resistant biotypes. By using dose-response curves it was possible to verify that the level of resistance (GR50 of the resistant biotype (R) divided by the GR50 of the susceptible biotype (S)) is between 6,15 and 10,79 for the biotypes of the species Conyza canadensis and between 1,52 and 14,75 for the biotypes of the species Conyza bonariensis. With regard to the best control herbicide alternatives of control, comparing horseweed plants at different phonological stages, it was observed that the control level (%) in plants at 10 leaves of development were of 88.0, 81.5 and 76.6% respectively for the treatments with glyphosate + bromacil + diuron (1,440 + 1,200 + 1,200 g ha-1), glyphosate + atrazina (1,440 + 1,500 g ha-1) e glyphosate + diuron (1,440 + 1,500 g ha-1), considered as the most effective treatments; for the plants at reproductive stage, the best alternatives of control were the treatments with ammonium glufosinate. The growth based on shoot and root dry biomass and leaf area of the resistant biotypes of both species compared to the susceptible biotype of the respective species were lower than of the resistant plants, but the resistant plants have higher seed production potential, The humidity was the main factor to interfere the germination on Matão-SP. Therefore, it is possible do conclude from this research that the biotypes studied are resistant to glyphosate, and they have the same competitiveness compared to the susceptible ones; the efficacy of the alternative herbicides for management of the resistant biotypes of horseweed to glyphosate depends on the development stage of the weed.

Grassy arable field margins provide important permanent habitats for arthropods in agroecosystems and due to their proximity to high input areas, are exposed to pesticide drift. The aims of this thesis are to determine the likely effects of glyphosate drift in arable field margins by examining patterns of a medium quality spray drift intercepted by plant species in buffer strips and the effects of glyphosate on non-target field margin arthropods. Levels of mediumquality spray drift, analogous to herbicide drift, intercepted by field margin plant species in field boundaries were significantly reduced by inclusions of 2m and 6m wide buffer strips. Levels of spray drift interception varied between plant species and were related to plant height and leaf area. Dose-response testing of glyphosate against field margin plant species was done to establish inherent susceptibilities to the herbicide. Many species appeared to be unaffected by high levels of glyphosate (1800g ha^-1), while others had relatively high ED₅₀s that were unlikely to be exceeded by UK recommended rates of glyphosate. It was noted that lack of exposure to interspecific competition may have enhanced the plant species tolerance to high levels of glyphosate. Different rates of glyphosate were screened against the non-target arthropods Lepthyphantes tenuis (Araneae) and Leptopterna dolabrata (Heteroptera) to assess toxicity. Glyphosate was found to be non-toxic, however, applications of glyphosate to food plants increased mortality in L. dolahrata. In a field experiment, glyphosate applications of more than 360g ha^-1 to a grassy arable field margin reduced Araneae, Heteroptera and Carabidae abundance. Community analyses (DCA) indicated that communities in the field margins exposed to more than 360g ha^-1 glyphosate were distinct from unsprayed field margins. It is predicted that drift of field applied glyphosate at rates greater than 1440g ha^-1 would reduce phytophagous Heteroptera and Gonalium rubens (Araneae) abundance.

A seleção de biótipos de plantas daninhas resistentes ao herbicida glyphosate no Brasil vem crescendo a cada ano em conseqüência principalmente da dependência dos principais sistemas de produção a este herbicida. Este fenômeno é evidente na citricultura brasileira, onde o glyphosate é o principal herbicida utilizado no controle de plantas daninhas há anos. As infestações da planta daninha conhecida como buva na citricultura é composta da mistura de duas espécies, Conyza canadensis e C. bonariensis, que apresentam ciclo de vida anual ou bianual, e são espécies altamente adaptadas a agroecossistemas com baixo distúrbio mecânico no solo, sendo nos sistemas de produção citrícolas altamente prolíficas. A suspeita de seleção de biótipos de buva resistente ao herbicida glyphosate motivou o desenvolvido desta pesquisa com o objetivo de comprovar a existência de biótipos resistentes, identificar suas principais características de crescimento e estudar alternativas de controle desses biótipos. A comprovação da existência dos biótipos resistentes ao glyphosate foi feita através de curvas dose-resposta, onde se verificou que o nível de resistência (GR50 do biótipo resistente (R) dividido pelo GR50 do biótipo suscetível (S)) está entre 6,15 a 10,79 para os biótipos da espécie Conyza canadensis e entre 1,52 a 14,75 para os biótipos da espécie Conyza bonariensis. Com relação ao estudo de herbicidas alternativos ao glyphosate no seu controle, comparando a aplicação dos herbicidas estudados em plantas de buva sob dois estádios fenológicos, verificou-se que os níveis de controle (%) em plantas com até 10 folhas de desenvolvimento foram de 88, 81,5 e 76,6% respectivamente para os tratamentos com glyphosate + bromacil + diuron (1.440 + 1.200 + 1.200 g ha-1), glyphosate + atrazina (1.440 + 1.500 g ha-1) e glyphosate + diuron (1.440 + 1.500 g ha-1), considerados como mais eficazes; já em plantas em estádio de desenvolvimento reprodutivo, as melhores alternativas de controle foram os tratamentos que continham o herbicida amônio glufosinato 400 g ha-1. O crescimento vegetativo, baseado na biomassa seca de raízes e parte aérea e área foliar, dos biótipos resistentes de ambas as espécies comparados com o seu respectivo biótipo suscetível foi menor que o das plantas resistentes. A umidade demonstrou-se como o principal fator de interferência da germinação de buvas na região de Matão-SP. Dessa maneira, a presente pesquisa comprovou a resistência dos biótipos estudados ao herbicida glyphosate, destacando as diferenças de crescimento entre os biótipos; a eficácia dos herbicidas alternativos de manejo dos biótipos resistentes de buva ao glyphosate é dependente do estádio fenológico de desenvolvimento da planta daninha, sendo o herbicida amônio-glufosinato excelente alternativa de controle do biótipo resistente ao glyphosate. / The selection of weed biotypes resistant to glyphosate in Brazil has been increasing each year, as a consequence of the over reliance of the main cropping systems to this herbicide. This phenomenon is observed in citrus production systems, where glyphosate is the main herbicide used for weed control for several years. The infestation of the weed known as horseweed is composed by the mixture of two species, Conyza canadensis and Conyza bonariensis, that present annual or biannual life cycle, and adaptation to agroecossystems with low mechanical disturbance in the soil, being in the citrus production systems highly prolific. The suspicion of glyphosate resistant biotypes of horseweed motivated the development of this research with the objective of detecting the existence of resistant biotypes, identifying the main characteristics of growth and development and studying alternatives of control of these resistant biotypes. By using dose-response curves it was possible to verify that the level of resistance (GR50 of the resistant biotype (R) divided by the GR50 of the susceptible biotype (S)) is between 6,15 and 10,79 for the biotypes of the species Conyza canadensis and between 1,52 and 14,75 for the biotypes of the species Conyza bonariensis. With regard to the best control herbicide alternatives of control, comparing horseweed plants at different phonological stages, it was observed that the control level (%) in plants at 10 leaves of development were of 88.0, 81.5 and 76.6% respectively for the treatments with glyphosate + bromacil + diuron (1,440 + 1,200 + 1,200 g ha-1), glyphosate + atrazina (1,440 + 1,500 g ha-1) e glyphosate + diuron (1,440 + 1,500 g ha-1), considered as the most effective treatments; for the plants at reproductive stage, the best alternatives of control were the treatments with ammonium glufosinate. The growth based on shoot and root dry biomass and leaf area of the resistant biotypes of both species compared to the susceptible biotype of the respective species were lower than of the resistant plants, but the resistant plants have higher seed production potential, The humidity was the main factor to interfere the germination on Matão-SP. Therefore, it is possible do conclude from this research that the biotypes studied are resistant to glyphosate, and they have the same competitiveness compared to the susceptible ones; the efficacy of the alternative herbicides for management of the resistant biotypes of horseweed to glyphosate depends on the development stage of the weed.

The naturally occurring monoterpene 1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane 1, commonly named 1,8-cineole and the major component in the leaf oil of many eucalypts, exhibits bioactivity, being potentially antimicrobial and pesticidal. A range of derivatives of 1,8-cineole and its naturally occurring isomeric analogue 1,4-cineole 2, 1-isopropyl-4-methyl-7-oxabicyclo[2.2.1]heptane, were synthesised. High-cineole eucalyptus oil, 1,8-cineole and the 1,8- and 1,4-cineole derivatives were shown to have a dose dependent pre-emergence and post-emergence herbicidal activity against radish (Raphanus sativus var. Long Scarlet), and annual ryegrass (Lolium rigidum) in laboratory bioassays. A postulated increase in activity of the ester derivatives due to metabolic cleavage into their bioactive hydroxy-cineole and carboxylic acid portions after uptake by the plant was not observed. The role of mallee eucalypts in the rehabilitation of degraded farmland in the Western Australian wheat belt, uses of eucalyptus oil and the bioactivity of essential oils and naturally occurring terpenes, with particular emphasis on eucalyptus oil and 1,8-cineole, were reviewed. The review encompasses allelopathic and herbicidal activity, insecticidal, acaricidal and antimicrobial activity. 1,8-Cineole compounds functionalised at position 3 of the cyclohexane ring and the 1,4-cineole derivatives were chemically synthesised whilst 2-endo-hydroxy-1,8-cineole was obtained as the primary metabolite of a novel bacterium grown on 1,8-cineole as sole carbon source. The bacteria were isolated by inoculating liquid growth medium containing 1,8-cineole as carbon source with aliquots of deionised water in which eucalyptus leaves had been stirred. Sequencing of its 16S rRNA gene identified the bacteria as belonging to the order Sphingomonadales, family Sphingomonadaceae and genus Sphingomonas. Growth curves for the bacterium are described and a metabolic pathway for the microbial degradation of 1,8-cineole is confirmed. Bacteria were cultured on a 20 L scale to provide sufficient 2-endo-hydroxy-1,8-cineole for the herbicidal bioassays.

Field and greenhouse studies were conducted to assess the effects of row-spacing on diseases, weed control, herbicide persistence and plant development in peanut. Tebuconazole, when averaged across cultivars and row spacing, effectively controlled white mold (57%) and rust (58%). Azoxystrobin also controlled white mold (58%) and controlling rust (44%). Both fungicides reduced leaf spot severity in the conventional and twin rows when compared to untreated plots. Twin rows showed a 10% yield increase compared to the conventional planting. Both diclosulam and imazapic, when applied to twin rows at the full and reduced rate, provided better yellow nutsedge control than when applied to the conventional row. Twin rows yielded higher than the conventional rows when averaged across herbicides in one year. All full rate herbicide treatments enhanced yield over the untreated check. Diclosulam and imazapic treated soil sampled 60 DAP adversely affected all four crops. The advantage of planting peanuts in twin rows to reduce diclosulam and imazapic residual concentrations was not apparent. Georgia Green and Tamrun 96 planted in twin rows at three of the four locations in 1999 and 2000 yielded higher than peanuts planted in conventional rows. Yields were comparable to twin-row spacings that had higher plant densities. Georgia Green and Tamrun 96 planted in conventional rows, in most cases, had higher yields than narrow-rows. Measurements for plant diameter, pod distribution, and main stem length were higher with Tamrun 96 at most row spacings and planting densities compared to the respective Georgia Green planting densities and row spacings. Both cultivars when planted in twin or narrow rows at all planting densities did not enhance maturity when sampled late season. Georgia Green and Tamrun 96 when planted in conventional rows had the most pods/plant compared to the narrow and twin row spacing. No clear evidence was found to suggest that peanuts grown in narrow or twin rows increased white mold disease incidence. Grades for Georgia Green were higher than Tamrun 96 when planted in twin rows at the standard planting density. Tamrun 96 in twin rows at the standard planting density had a higher grade than when planted in conventional rows at the low planting density.

Clomazone is a carotenoid biosynthesis inhibitor commonly used as a preemergence and postemergence herbicide in rice for the control of grass weeds. Rice injury can occur and symptoms are often associated with soil characteristics and environmental conditions. The objective of this research was to investigate how environmental conditions and planting density influence clomazone injury in rice plants. Also, different fertility treatments were assessed to determine if remediation from clomazone injury occurred. Field studies were conducted in 2008 and 2009 to determine the role of planting date, planting density and soil characteristics on clomazone injury in rice plants. Also, another field study was conducted in 2010 to assess any clomazone injury remediation benefits selected fertility treatments might have in rice cropping systems. In the 2008 and 2009 field studies, hybrid rice was seeded at three densities that comprised a range of slightly lower, slightly higher and commonly recommended planting rates. Two planting dates, March and April, were a test parameter to simulate early and optimal planting dates. Two locations with different soil characteristics, near Eagle Lake and Beaumont, TX, were the study sites. Clomazone herbicide treatments were applied at different rates and timings following planting. Visual injury ratings and yield data were collected during this two-year, two location study. Clomazone injury in rice was more severe in the coarse-textured soils planted at the early, March planting date near Eagle Lake. Visual injury ratings as high as 90% were observed in some plots. Injury was less severe in the April planting date near Eagle Lake, and at both planting timings near Beaumont. In both locations, clomazone injury did not translate into yield loss at any seeding rate or planting timing. In 2010, field studies were conducted near Eagle Lake and Ganado, TX to assess fertility-based clomazone injury remediation. In one experiment, hybrid rice plots were subject to linearly increasing rates of clomazone herbicide to produce a standard curve of clomazone injury. In the second experiment, a uniform, label rate of clomazone was applied to induce injury for the assessment of the effect of fertility amendments on clomazone-injured rice. Fertility treatments consisted of nitrogen-based fertilizers and foliar-applied iron sulfate and magnesium sulfate. Visual injury ratings, plant height, and yield were collected during the study. Also, tissue samples were collected three times for laboratory analysis of chlorophyll content. In the standard curve experiment, herbicide injury increased with increasingly higher rates of clomazone applied. The highest visual injury was observed in plots receiving the highest rates of clomazone. In the remediation experiment, fertility treatments had a significant effect in only one tissue-sampling event at Eagle Lake as determined by laboratory analysis for chlorophyll content. Fertility amendments did not have a significant effect on visual injury ratings at either location at any assessment event. Specific fertility treatments significantly increased plant height in three measurement events, and yield at the Ganado locations. Plots receiving treatments containing nitrogen fertilizers produced taller plants at both locations, and increased yield at the Ganado location.

Known as Golden Algae in popular media, Prymnesium parvum causes harmful algal blooms. When stressed, it secretes increased amounts of toxic chemicals called prymnesins, which have resulted in major fish kills in Texas. Although many options exist for mitigation of blooms, a feasible protocol for control of blooms on large-scale impoundments has yet to be identified. Chemical control of P. parvum using six different enzyme inhibiting aquatic herbicides was explored in laboratory experiments. Of the six chemicals screened, one (Flumioxazin) was selected for further study due to a significant decrease in P. parvum cell numbers with increasing chemical concentration. It was applied to natural plankton communities during in-situ experiments (Lake Granbury, Texas). The first experiment was conducted during a period of P. parvum bloom initiation (March) and the second experiment conducted during a post bloom period (April). Experiments were carried out in 20 L polycarbonate carboys covered in 30% shade cloth to simulate natural light, temperature and turbulence conditions. Flumioxazin was additionally screened in the laboratory on the common game/forage fish bluegill sunfish (Lepomis macrochirus) for six weeks with weekly re-application of flumioxazin to treatment tanks. Cell counts via light-microscopy, showed the chemical flumioxazin caused significant decreases in P. parvum, but no significant differences in zooplankton abundance during the period of bloom initiation. However, significant decreases in adult copepods were observed during the post bloom period, most likely due to decreased light penetration and inhibition of the photosensitive mode of action, but no significant decreases in P. parvum. No significant effects of flumioxazin were observed on growth, survival or feed conversion ratio for L. macrochirus.

Field and greenhouse studies were conducted to assess the effects of row-spacing on diseases, weed control, herbicide persistence and plant development in peanut. Tebuconazole, when averaged across cultivars and row spacing, effectively controlled white mold (57%) and rust (58%). Azoxystrobin also controlled white mold (58%) and controlling rust (44%). Both fungicides reduced leaf spot severity in the conventional and twin rows when compared to untreated plots. Twin rows showed a 10% yield increase compared to the conventional planting. Both diclosulam and imazapic, when applied to twin rows at the full and reduced rate, provided better yellow nutsedge control than when applied to the conventional row. Twin rows yielded higher than the conventional rows when averaged across herbicides in one year. All full rate herbicide treatments enhanced yield over the untreated check. Diclosulam and imazapic treated soil sampled 60 DAP adversely affected all four crops. The advantage of planting peanuts in twin rows to reduce diclosulam and imazapic residual concentrations was not apparent. Georgia Green and Tamrun 96 planted in twin rows at three of the four locations in 1999 and 2000 yielded higher than peanuts planted in conventional rows. Yields were comparable to twin-row spacings that had higher plant densities. Georgia Green and Tamrun 96 planted in conventional rows, in most cases, had higher yields than narrow-rows. Measurements for plant diameter, pod distribution, and main stem length were higher with Tamrun 96 at most row spacings and planting densities compared to the respective Georgia Green planting densities and row spacings. Both cultivars when planted in twin or narrow rows at all planting densities did not enhance maturity when sampled late season. Georgia Green and Tamrun 96 when planted in conventional rows had the most pods/plant compared to the narrow and twin row spacing. No clear evidence was found to suggest that peanuts grown in narrow or twin rows increased white mold disease incidence. Grades for Georgia Green were higher than Tamrun 96 when planted in twin rows at the standard planting density. Tamrun 96 in twin rows at the standard planting density had a higher grade than when planted in conventional rows at the low planting density.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.