This thesis concerns on biology, occurrence and especially, herbicide regulation of Viola arvensis Murray on arable land. On the land of the farm DZV NOVA Bystřice a small-plot experiment focused on monitoring and regulation of Viola arvensis was carried out. This experiment was carried out from September 2012 to January 2014 on three crops (winter wheat, winter barley and winter rape) in three locations. In the theoretical part we describe the biology and occurrence of this frequent weed. The aim of the thesis was to evaluate the abundance of Viola arvensis and other weed species and verify the effect of different herbicides on Viola arvensis and other weeds. The effectiveness of the tested herbicide combinations was statistically significant for Viola arvensis and also for the other weeds (P 0, 05). The exceptions were Veronica persica, Geranium pussilum and Hordeum vulgare, where the effectiveness of these agents was not proved (P > 0, 05). The results summarize the numbers of weed species and effectiveness of applied herbicides. Viola arvensis was the most frequent weed species found on the examined sites. The effectiveness of herbicide agents used against this weed was very high. The highest was by preparations Maraton + Glean 75 WG, Maraton + Logran 20 WG, Cougar Forte + Logran 20 WG a Sumimax + Glean 75 WG (100 %). Lower was by preparations Butisan 400 SC + Command 36 SC (80 %) a Butisan Star + Garland Forte (75 %). In the winter barley and winter wheat, the applied herbicides were 100% effective, only in the winter rape the effectiveness was lower (75 - 80%). I can confirm the initial hypothesis about the effectiveness of the different herbicides on field pansy because their effectiveness differed.

Les diatomées sont des microalgues ubiquistes d'une diversité exceptionnelle. Cela en fait de bons indicateurs de la qualité des écosystèmes aquatiques et sont utilisées depuis plus de 50 ans. Depuis l'année 2000, la Directive Cadre Européenne sur l'Eau impose leur utilisation pour évaluer la qualité écologique des cours d'eau. Un cadre typologique doit être utilisé afin de comparer des rivières comparables entre elles, c'est-à-dire des rivières de mêmes régions bioclimatiques, coulant sur les mêmes substrats géologiques et à des altitudes comparables. Différentes classifications écorégionales ont été définies sur la base de ces paramètres. Nous avons montré qu'à une échelle couvrant 4 pays (Espagne, France, Italie, Suisse) et à une régionale (Nord-est de la France), les écorégions et la géologie sont déterminantes pour expliquer les communautés. Les paramètres caractérisant la pollution sont moins importants. Contrairement à certains auteurs, nous n'avons pas observé d'homogénéisation des communautés lorsque le niveau de pollution augmente. D'autre part nous n'avons pas observé de communautés restreintes géographiquement : cela permettrait de rassembler des écorégions distinctes géographiquement mais présentant les mêmes caractéristiques physiques. Les diatomées présentent une diversité spécifique très importante qui peut être un frein à leur utilisation en routine. Nous avons montré qu'en augmentant la précision de détermination (de la subdivision à l'espèce), les performances d'évaluation de la pollution augmentait mais beaucoup moins que le nombre de taxons. Les performances d'évaluation entre le genre et l'espèce sont d'ailleurs proches, alors qu'il y a dix fois plus d'espèce que de genres. Nous avons montré aussi que des métriques simplificatrices (formes de vie, guildes écologiques) permettaient d'évaluer aussi bien le niveau en nutriment que des indices diatomiques basés sur les espèces. Ces métriques apportent des informations supplémentaires en termes de structure de biofilm qui ne sont accessible aux données en espèce. Enfin, la pollution des rivières par les micropolluants devient une préoccupation sociétale croissante. Nous avons émis l'hypothèse que les diatomées pouvaient être de bons candidats pour évaluer la pression en herbicides. Quatre expérimentations de 2 mois ont été réalisées en mésocosmes lotiques. Nous avons montré que les diatomées vivant entourées de matrices polysaccharidiques épaisses étaient plus résistantes aux pesticides dissous. Au contraire les diatomées présentant une surface cellulaire de contact importante avec l'eau étaient défavorisées. Ce type de métrique pourrait être utilisé in situ à plus large échelle. Nous concluons sur l'intérêt d'intégrer ces métriques à la bioindication par les diatomées. Mais également nous soulignons l'importance de croiser la phylogénie et l'écologie pour mieux comprendre quelles pressions environnementales ont forcées les diatomées à s'adapter. Si ces pressions peuvent être reliées à des pressions anthropiques, la bioindication par les diatomées en sera améliorée. / Diatoms are ubiquitous microalgae of an extreme diversity. This made them good indicators of aquatic ecosystems quality and they are used since 50 years for this purpose. Since year 2000, the European Water Framework Directive requires their use to assess the ecological quality of watercourses. A typological framework has to be used in order to compare comparable rivers between each other, that is, rivers of the same bioclimatic regions, flowing on the same geological substrate at similar altitudes. Various ecoregional classifications were defined on the basis of these parameters. We showed at a scale covering 4 countries (Spain, France, Italy and Switzerland) and at a regional scale (north-east France) that ecoregions and geology are determinant to explain communities. Parameters characterizing pollution were less important. Unlike some authors, we did not observe any homogenization of the communities when pollution level was increasing. Moreover, we did not observe geographically restricted communities: this would enable to aggregate ecoregions geographically distinct but presenting the same physical characteristics. Diatoms display a very important specific diversity which can be a problem for their routine use. We showed that when increasing determination precision (from sub-division to species), pollution assessment performances were increasing but much less than the number of taxa. Assessment performances between genus and species are similar anyway, whereas there are ten time more species than genera. We also showed that using simplifying metrics (life-forms, ecological guilds) enable assessing nutrient level as well as diatom indices based on species. These metrics bring additional information about biofilms structure that is not available with species data. At last, micropollutants pollution in rivers is of increasing concern to citizens. We hypothesized that diatoms could be good candidates to assess herbicide pressure. Four experiments lasting 2 months were conducted in lotic mesocosms. We showed that diatoms surrounded by thick exopolysaccharid matrices were more resistant to dissolved pesticides. On the over hand, diatoms presenting an important cell surface contact with water were disadvantaged. This kind of metric could be used in situ at a larger scale. We conclude on the interest to integrate such metrics to diatom bioassessment. But we also strength the importance to cross phylogeny and ecology to better understand which environmental pressure forced diatoms adapt. If these pressures can be related to anthropogenic pressures, diatom bioassessment will be improved.

Research was conducted at the Mississippi State University Delta Research and Extension Center from 2015 to 2018 to (1) determine the effects of sub-lethal concentrations of paraquat, metribuzin, fomesafen, and cloransulam-methyl applied at different rice growth stages, determine the effects on rice growth of simulated off-target paraquat applications at varying concentration based on a proportionally decreased carrier volume characterize rice response to a sub-lethal concentration of paraquat in combination with common POST and residual herbicides, assess whether starter N fertilizer or different N fertilizer management strategies can aide in rice recover after exposure to a sub-lethal concentration of paraquat, and define a maximum soil concentration of S-metolachlor that will allow rice to germinate and emerge. Rice yield was negatively affected following exposure to paraquat applied any time after rice emergence. Paraquat applications to rice in early reproductive growth reduced rough rice yield and seed germination the greatest. Paraquat plus metribuzin injured rice 68 to 69% 14 and 28 d after treatment (DAT), which was 10 to 13% greater than following paraquat alone or paraquat plus fomesafen. Pooled across metribuzin and fomesafen treatments, paraquat reduced rough rice yields 23%. Paraquat plus 10 different residual herbicides injured rice ≥51% 28 DAT and reduced rough rice yields ≥21%. In spite of starter N fertilizer applications, paraquat injured rice ≥41%, reduced height 57%, reduced dry weight prior to flooding 77%, delayed maturity 10 d, reduced dry weight at maturity 33%, and reduced rough rice yield 35%. Similar results were observed in the N Fertilizer Timing Study. Soil concentrations of s-metolachlor 28 DAT were 30, 31, 32, 36, 61, and 488 ppm following exposure to s-metolachlor applied at 0, 1/64, 1/32, 1/16, 1/4, and 1X concentration. A soil analysis would be the best option to determine levels of s-metolachlor prior to planting rice if an off-target herbicide movement containing s-metolachlor occurred. These data indicate that paraquat can have negative impact on rice growth and development. Therefore, it is crucial that if environmental conditions are conducive for off-target herbicide movement extreme caution should be exercised when applying paraquat adjacent to fields devoted to rice production.

Determining the basis of intraspecific herbicide tolerance was expected to be a useful way of revealing factors which are regulated by safeners in providing their protective effect. Differential tolerance to the chloroacetanilide herbicide metolachlor and the thiocarbamate herbicide EPTC was examined in 11 corn hybrids. Tolerance to one of these herbicides does not imply similar tolerance to the other. Detoxication of these herbicides in plants is mediated via conjugation with glutathione (GSH). GSH levels from 1.8 to 2.4 µmol/g fresh weight were determined for the eleven corn hybrids tested. There was no correlation between GSH content and herbicide tolerance. The monooxygenase inhibitor piperonyl butoxide (PBO) acted synergistically with EPTC on 8 of the tested corn hybrids. A Similar antagonism by the oxygen evolving compound calcium peroxide provided additional evidence for the importance of oxidative processes in EPTC tolerance which were not important in determining metolachlor tolerance. The more rapid absorption and greater accumulation of ¹⁴C-metolachlor by 'Northrup-King 9283' corn relative to 'Cargill 7567' corn at least partially explains the increased susceptibility of the former hybrid to metolachlor. The in vitro metabolism of ¹⁴C-metolachlor was similar for both hybrids. A lag in the expression of glutathione S-transferase (GST) activity during early seedling development of 'Northrup-King 9283' corn may be of additional significance in its limited tolerance to metolachlor. The safener benoxacor was effective in protecting 'Northrup-King 9283' and other susceptible corn hybrids from metolachlor injury. Benoxacor had no effect on metolachlor uptake or the rate of non-enzymatic conjugation of metolachlor. Seedlings of 'Cargill 7567' and 'Northrup-King 9283' treated with 1 µM benoxacor metabolized metolachlor to the GS-conjugate at a rate 1.7 times that of untreated seedlings. GST activity was stimulated by 35% by similar treatment. GST isozymes with metolachlor conjugating activity (GST-metolachlor activity) were found in the cytosol and microsomal fractions of corn extracts. At least two GST-metolachlor isozymes were separated by DEAE-Sepharose chromatography. The activity of both isozymes was increased by benoxacor treatment. It appears that benoxacor regulates metolachlor tolerance by inducing GST isozymes that consequently increase the rate of metolachlor detoxication. / Ph. D.

The purpose of this research was to evaluate a common lambsquarters (Chenopodium album) collection from Westmoreland County, Virginia, which exhibited a differential response to glyphosate treatments as compared to most other common lambsquarters. Plants from this site that survived glyphosate applications were collected in both 2002 and 2004. Greenhouse studies were conducted on F1, F2, and F3 progeny from this collection and compared to a wild type collection from Montgomery County, Virginia. Evaluations were conducted on these plants treated with a range of glyphosate rates. F1 progeny of the Westmoreland plants from both 2002 and 2004 collections showed reduced response to glyphosate relative to the Montgomery collection. Vigor reduction of F1 progeny from three 2004 Westmoreland source plants with 0.84 kg ae/ha of glyphosate ranged from 66 to 85% at 28 days after treatment (DAT), compared to 89% for the Montgomery collection. Evaluation of four Westmoreland F2 common lambsquarters lines derived from 2002 collections indicated significant differences in glyphosate sensitivity. Fifteen F2 lines were generated from 2004 collections from each of three Westmoreland source plants and from the Montgomery source. For the least sensitive Westmoreland source, vigor reduction ranged from only 24 to 36% across F2 lines in response to 1.68 kg/ha of glyphosate at 28 DAT, relative to 55 to 100% for the Montgomery source. I50 estimates for fresh weight reduction were 0.91 and 0.32 kg/ha, for these sources, respectively. Sequential treatments of 0.42, 1.26, and 1.68 kg/ha applied at three-week intervals to the least susceptible 2004 Westmoreland F2 line resulted in only 37% vigor reduction and no mortality among 360 treated plants. Growth chamber studies were also conducted on the F2 progeny of these sources to determine if differential growth responses occur in noncompetitive environments and in the absence of glyphosate treatment. Generally, few differences were observed among the Westmoreland and Montgomery collections in growth parameters including height, leaf number, leaf area, leaf size, shoot weight, and reproductive output. However, significant differences were observed with regard to root weight, root length, and root density. In germination studies, it was determined that the Montgomery source had significantly faster and greater seed germination than the Westmoreland source. The susceptibility of F3 seedlings to glyphosate varied significantly with respect to F2 parent line and glyphosate rate. Mortality of 100% was observed in F3 seedlings from the Montgomery source in response to the 3.36 kg ae/ha glyphosate rate, while no mortality was observed in Westmoreland F3 seedlings in response to this glyphosate rate. / Master of Science

Fields studies conducted in 1987 and 1988 determined the weed control efficacy of ICIA-0051 and SC-0774 in conventional and no-till systems of corn (<i>Zea mays</i> L.) culture. Results of the preemergence and postemergence applications of ICIA-0051, across all treatments after 8 weeks, showed 85% control or better of triazine-resistant smooth pigweed (<i>Amaranthus hybridus</i> L.), while fall panicum (<i>Panicum dichotomiflorum</i> Michx.) control ranged from 43 to 87%. Giant ragweed (<i>Ambrosia trifida</i> L.) control ranged from 30 to 95%, while control of ivyleaf morningglory (<i>Ipomoea hederacea</i> (L.) Jacq.) was below 75% in the preemergence treatments and ranged from 89 to 99% in the postemergence treatments. In general, the addition of atrazine to the pre- and postemergence treatments of ICIA-0051 improved weed control. SC-0774 treatments gave 85% or better control of fall panicum, but inadequate broadleaf weed control (75% or worse). Soil mobility studies using soil thin-layer chromatography and soil leaching columns indicated that the movement of ICIA-0051 was highly negatively correlated with the organic/humic matter fraction. Although the mobility patterns were similar, ICIA-0051 was more mobile than SC-0774, which was more mobile than atrazine. A comparison of ICIA-0051 across soils indicated that the order of mobility was Appling loamy sand (Rf = 6.4) > Davidson clay (Rf = 5.6) > Bojac sandy loam (Rf = 5.0) = Frederick silt loam (Rf = 4.9) > Hyde silty clay loam (Rf = 1.1). Other soil properties such as the clay content and pH were not strongly correlated with ICIA-0051 movement. Results of the adsorption/desorption studies indicated that the organic/humic matter fraction was primarily responsible for the binding and retention of ICIA-0051 across the five soils investigated. Based on the K constants derived from the Freundlich equation, the order of adsorption was Hyde > Frederick > Davidson = Bojac > Appling. The desorption results indicated that ICIA-005l was not tightly bound to the soil particles, with losses between 20 and 50% of the amount adsorbed after two desorptions. Results of the greenhouse persistence study, using mustard (<i>Brassica kaber</i> L.) as a bioassay species, indicated that ICIA-0051 was more biologically available than atrazine. Similar to the adsorption and leaching results, the persistence of ICIA-0051 was highly positively correlated with the soils’ organic matter. Regardless of the rate used, crop injury decreased over time, although the highest rate (1 ppm of ICIA-0051) showed significant crop injury even after 6 months in several soils in the greenhouse studies. / Ph. D.

Response of barley (<i>Hordeum vulgare</i> L.) and wheat (<i>Triticum aestivum</i> L.) to root-applied chlorsulfuron (2-chloro N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino] carbonyl] benzenesulfonamide), a herbicide for use in small grains, was investigated. The results showed that, although wheat roots take up more chlorsulfuron than barley roots, barley was less tolerant to chlorsulfuron and chlorsulfuron was more mobile in barley. This study indicated that difference in uptake or translocation cannot explain the differential response of the two species to root-applied chlorsulfuron. In an interaction study, significant chlorsulfuron antagonism on ryegrass (<i>Lolium multiflorum</i> Lam.) control by diclofop {(±)[-2-[4-(2,4-dichlorophenoxy) phenoxy) propanoic acid} was observed. Greenhouse experiments showed that the tolerance of corn (<i>Zea mays</i> L.) to chlorsulfuron and metsulfuron (2-[[[[(4-methoxy-6-methyl-l,3,5-triazin- -2-yl) amino] carbonyl] amino] sulfonyl] benzoic acid) was greatly increased by seed dressing with the herbicide safener NA (1,8-naphthalic anhydride). The soil behavior of chlorsulfuron was studied in the field, greenhouse and laboratory. In the field, corn adequately tolerated soil residues present 10 months following postemergence application of chlorsulfuron at 10 to 120 g/ha. However, at the same site and rates, residues from chlorsulfuron injured corn when sampled 2 months after application. In laboratory studies chlorsulfuron was moderately adsorbed by organic matter but showed low affinity to clay. R_f values calculated from soil thin-layer chromatography closely correlated with the mobility of chlorsulfuron leached with 16.8 cm of water over a 14-day period in hand-packed soil columns. In the soil thin-layer chromatography, chlorsulfuron mobility was positively and negatively correlated with pH and organic matter, respectively. The results indicated that chlorsulfuron could be mobile in low organic matter and non-acidic soils. The relationship of chlorsulfuron phytotoxicity to soil physical and chemical properties was also evaluated. Organic matter was inversely related to chlorsulfuron phytotoxicity while no such relationship to clay content was observed. The adsorption of chlorsulfuron decreased with increasing soil pH whereas desorption was greater at alkaline pH. / Ph. D.

Italian ryegrass (Lolium perenne spp. multiflorum) is a common weed management problem in turfgrasses, cereals and non-crop areas in the United States. In Oregon, the number of populations with multiple-resistance continues to increase. To manage these resistant populations, the resistance patterns must be determined. In this study, five Italian ryegrass populations (CT, R1, R2, R3 and R4) from two cropping systems were studied for resistance patterns and mechanisms. The CT population is from a Christmas tree plantation and was resistant to at least six herbicides with four different mechanisms of action: atrazine, diuron (2.4-fold), glyphosate (7.4-fold), hexazinone (3.1-fold), imazapyr (1.8-fold), and sulfometuron. The resistant indices (RI) for sulfometuron and atrazine could not be calculated because 50% growth reduction for the CT population was not reached even with the highest rates applied, 17.6 kg ai ha⁻¹and 16 kg ai ha⁻¹, respectively, which are 16 times the recommended field application rates for this two herbicides. The CT population accumulated less shikimate than the S population. There were two mutations in the CT population, Trp591 to Leu in the ALS gene and Ser264 to Gly in the psbA gene, which explain the ALS and PII cross resistance, respectively. R1, R2, R3 and R4 were collected from annual cropping systems. All four populations were resistant to flufenacet. RIs for two populations, R2 and R4, were 8.4 and 5.9, respectively. R2 and R4 also were resistant to mesosulfuron-methyl, pinoxaden, quizalofop and clethodim. R4 was resistant to diuron, but R2 was not. An Asp-2078-Gly substitution in the ACCase gene was found in both R2 and R4 populations, while another Ile-2041-Asn substitution in the ACCase gene was found in the R4 population. These mutations explain the ACCase cross resistance in the R2 and R4 populations. The mechanisms for the glyphosate resistance in the CT population and the flufenacet resistance in R1, R2, R3 and R4 populations were not identified in this study. None of the five populations were resistant to the herbicide pyroxasulfone. / Graduation date: 2013

Red rice (Oryza spp.) is one of the main limiting factors of rice yield (O. sativa L.) in the world and particularly in the Rio Grande do Sul (RS) state Brazil. The Clearfield® technology is a viable and efficient tool for controlling such harmful plant by using imidazolinone herbicides in tolerant cultivars. However, herbicides may persist on the soil after the crop season in amount that could affect the future use of the area with other crops as well as with non tolerant rice cultivars. The persistence of this kind of herbicides is highly dependent on the soil s environmental conditions. It increases in low pH soils with high organic matter (MO) content, and under anaerobic conditions. The main way of herbicide dissipation is the biodegradations; they can be photolysis or be lixiviated bellow the roots absorption region. Two field experiments were carried out on lowland soil in Santa Maria-RS during 2006/2007. The first experiment (Chapter II) had the objective of determining the effect of nine soil tillages (four on no till or minimum till seeping and five, on conventional tillage) on the phytotoxicity of non tolerant rice. The residual effect of the herbicide Only® affected plants stand, tillering, panicle number and plant heights of cultivar IRGA 417, but did not affect the grain yield. Soil plowing decreased herbicide activity on the soil surface (0-3 cm) without affecting the variables assayed. The second experiment (Chapter III) had the objective of determining the effect of two soil tillages (no till- PD- and conventional tillage-PC) on imazethapyr degradation and leaching. Higher degradation of imazethapyr was registered on PC than on PD. Imazethapyr leaching until 20 cm regardless the tillage system. In PC, a uniform distribution of imazethapyr was observed in the first 15 cm of soil while in PD there was a lower concentration of imazethapyr at 0-5 cm, which accumulated at 5-15 cm deep. / O arroz-vermelho (Oryza spp.) é um dos principais fatores limitantes da produtividade de grãos do arroz irrigado (O. sativa L.) no mundo e em particular do estado do Rio Grande do Sul (RS) Brasil. A tecnologia Clearfield® é uma ferramenta viável e eficiente para o controle desta planta daninha, mediante o uso de herbicidas da família das imidazolinonas junto com cultivares tolerantes a estes herbicidas. No entanto, os herbicidas podem permanecer no solo após o cultivo, em quantidade que pode comprometer a utilização futura da área com outras culturas, ou mesmo com cultivares de arroz não tolerante (NT). A permanência destes herbicidas no solo é muito dependente das condições ambientais e de solo, aumentando sua persistência em solos com pH baixos, com altos conteúdos de matéria orgânica (MO), argila e em condições de anaerobioses. A principal via de dissipação destes herbicidas é a microbiana, podendo também, sofrer fotólises ou serem lixiviados para fora da área de absorção das raízes. Foram conduzidos dois experimentos sob solo de várzea, em Santa Maria-RS no ano agrícola 2006/07. O primeiro experimento (Capítulo II) teve como objetivo determinar o efeito de nove manejos de solo (quatro sob plantio direto ou semidireto e cinco sob plantio convencional), na fitotoxicidade do arroz não tolerante. O efeito residual do herbicida Only® afetou o estande de plantas, perfilhamento, número de panículas e a estatura da cultivar não tolerante IRGA 417, porém não afetou a produtividade de grãos. O revolvimento do solo diminuiu a atividade do herbicida na camada superficial de solo (0-3 cm), embora não tenha afetado as variáveis analisadas. O segundo experimento (Capítulo III) teve como objetivo determinar o efeito de dois manejos de solo, plantio direto (PD) e plantio convencional (PC), na degradação e lixiviação do imazethapyr. Ocorreu maior degradação de imazethapyr no PC do que no PD. Imazethapyr lixiviou até 20 cm, independente do sistema de cultivo. No PC existe uma distribuição uniforme do imazethapyr nos primeiros 15 cm de solo e no PD existe menor concentração de imazethapyr de 0-5 cm, e acúmulo do herbicida de 5-15 cm de profundidade.

Much of the literature on herbicide resistant weeds suggests that farmers do not adopt resistance management practices on rented land to the same extent as on owned land. This study uses data from the USDA Agricultural Resource Management Survey for corn and soybeans to compare adoption of resistance management practices on owned and rented land analyzing national and regional data for a variety of weed management practices. There was little support for the hypothesis that renters adopted resistance management practices less than owners. In most cases, there was no significant difference in adoption rates. In cases where there were statistically significant differences, it was more common that resistance management practice adoption was higher on rented land than on owned land. The second part of this study estimated a hazard model to predict when resistance to glyphosate would first be detected in corn fields in a state. The model was used to test hypotheses about whether adoption of different weed management practices delayed or sped up the onset of resistance. The analysis found evidence that greater use of phosphinic acid herbicides (the herbicide family that includes glyphosate) sped up the onset of glyphosate resistant weeds.