Dissertations / Theses on the topic 'Effect of herbicide on'

Bibliography : leaves 159-184. This study found at least three mechanisms of resistance to the acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicides. A modified target -site was responsible for moderate and high resistance to herbicides at the whole plant level. Enhanced herbicide metabolism and reduced translocation of herbicide to the target site was observed in one resistant biotype each.

CGAr92194 {α-[1,3-dioxolan-2-yl-methoxy)imino]benzeneacetonitrile} is a herbicide safener that is used as a seed dressing agent (1.25 g ai/kg seeds) to protect grain sorghum [Sorghum bicolor (L.) Moench] against metolachlor [2-chloroi-N-(2-ethyl-6-methylphenyl-N-(2-methoxy1-methylethyl)acetamide] injury. The potential adverse phytotoxic effects and the mechanisms of the protective action of this safener were studied in laboratory experiments. Adverse phytotoxicity was assessed by comparing CGA-92194 and the herbicide safeners cyometrinil {(Z)-α[(cyanomethoxy)imino]benzeneacetonitrile} and flurazole [phenylmethyl 2-chloro-4-(trifluromethyl)-5-thiazolecarboxylate] for their effects on CO₂ fixation, protein, DNA, RNA and lipid syntheses of enzymatically isolated leaf cells of soybean [Clycine max (L.) Merr]. At physiological concentrations of less than 10 μM, CGA-92194, cyometrinil and flurazole were stimulatory of all metabolic processes. At 100 μM, the safeners were inhibitory of the five processes with flurazole being the most potent. The mechanisms of the safening action of CGA-92194 were studied by examining the potential interactions of this safener with metolachlor at the levels of uptake and macromolecular syntheses in enzymatically isolated leaf mesophyll protoplasts of grain sorghum. The influence of CGA-92194 on the in vitro reactivity of metolachlor with glutathione (GSH) and it metabolism by sorghum seedlings were also examined. When CGA-92194 and metolachlor were given simultaneously, CGA-92194 enhanced the uptake of ¹⁴C-metolachlor into the sorghum protoplasts in a concentration-dependent pattern. Thus, interference with herbicide uptake is not involved in the protective action of this safener Treatments with metolachlor and CGA-92194 in combination inhibited the incorporation of ¹⁴C-uracil, ³H-thymidine and ¹⁴C-acetate into sorghum protoplast macromolecules less than metolachlor given alone, suggesting the potential involvement of a competitive antagonism in the mechanism of action of CGA-92194. The metabolic activity and growth of sorghum seedlings grown from CGA-92194-pretreated seeds was significantly lower than that of seedlings grown from untreated seeds at 10 or 20 days after planting, The relationship of these effects of CGA-92194 to its safening action is unclear at the present time. CGA-92194 increased the in vitro chemica1 reactivity of metolachlor for GSH in a concentration-dependent pattern, Sorghum seedlings grown from safener-pretreated seeds enhanced ¹⁴C-metolachlor absorption and stimulated its metabolism via conjugation to GSH. This stimulation was reduced by tridiphane [2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethy1)- oxirane] a potent inhibitor of plant GSH-S-transference enzymes, These results indicate that a safener-induced stimulation of the spontaneous or enzymatic conjugation of metolachlor with GSH is most likely involved in the protective action of CGA-92194. It is suggested that the safening mechanism of action of CGA—92194 involves a sequence of multilevel interactions which together contribute to the overall protection of grain sorghum from metolachlor injury.
Ph. D.
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A series of experiments provided data to parameterize and validate a coupled herbicide fate and target plant species effects model. This simulation model is currently designed to predict responses of water hyacinth populations to treatments of the dimethylamine formulation of 2,4- dichloro-phenoxy acetic acid (2,4-D -DMA). Experiments investigated 1) the response of water hyacinth to varying exposures of 2,4-D (DMA); 2) the role of water hyacinth density and herbicide interception in treatment effectiveness using 2,4-D (DMA); and 3) the importance of root exposure to obtain control of water hyacinth using 2,4- D (DMA). Results demonstrated the importance of leaf or canopy interception of 2,4-D (DMA) sprays in obtaining control of water hyacinth populations. The critical threshold plant tissue concentration of 2,4-D (DMA) required to elicit maximum mortality (98%) was estimated to be approximately 12 mg 2,4-D per kg water hyacinth tissue (wet weight). Root uptake apparently plays little or no role in the effectiveness of this herbicide for controlling water hyacinth growth. Validation trials illustrated the efficacy of the current model. The model was validated with data from a field operation. This research has provided considerable insight into optimal use of this auxin-type herbicide for control of water hyacinth, a monocotyledon.

Bibliography: leaves 128-146. Study was undertaken to determine the occurence and species incidence of wild oats in a major cropping region of southern Australia. Population dynamic studies were undertaken at two sites to define the seed bank decline and emergence pattern of several wild oat populations over a three year period. Management studies were conducted to determine appropriate strategies for the control of wild oats in southern Australian farming systems.

Response of barley (Hordeum vulgare L.) and wheat (Triticum aestivum 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 (Lolium multiflorum Lam.) control by diclofop {(±)[-2-[4-(2,4-dichlorophenoxy) phenoxy) propanoic acid} was observed. Greenhouse experiments showed that the tolerance of corn (Zea mays 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.

Experiments were conducted to evaluate the effect of droplet size on the efficacy of translocated and non-translocated herbicides. Translocated and non-translocated herbicides provided similar control when comparing droplet size effect on efficacy. Medium and very coarse droplet sizes gave the greatest visible injury whereas coarse-sized gave the lowest visible injury assessments for most species. However, droplet size generally did not affect contact herbicide efficacy. Overall, droplet size was not a strong factor contributing to herbicide efficacy and often, differences were only between herbicides. Non-ionic surfactant solutions measured by a Sympatec droplet analysis system gave the highest percent of volume in droplets <150?m compared to other adjuvants. The lowest percent of volume in droplets <150?m was a 0.5x rate. A liquid herbicide formulation gave the largest percent of volume in droplets <150?m whereas an emulsifiable concentrate formulation was lowest. Percent volume in droplets <150?m was often related to the solution VMD.

Herbicide safeners (protectants, antidotes) are used to protect crop plants from herbicide injury. Currently our understanding of the mechanisms involved in the protection of plants by safeners is not well defined; therefore, investigations were conducted to elucidate the mechanism(s) of action of the oxime ether safeners. Molecular comparisons of selected herbicide-safener combinations using computer-aided molecular modeling revealed that the chemical structures of safeners and herbicides are very similar at the molecular level; and, indicate that these compounds could bind at the same active site of the target protein or they may serve as inducers of metabolic enzymes which detoxify herbicides. Metolachlor at 10 μM and seed-applied CGA-133205 had no effect on germination while treatment with seed-applied oxabetrinil significantly reduced germination of grain sorghum. Results from experiments on ¹⁴C-acetate incorporation into lipids indicate that metolachlor and the oxime ether safeners influence lipid metabolism causing a redistribution of carbon in the lipid fractions of germinating sorghum roots. Results from studies with acetyl-CoA carboxylase indicate that this enzyme is not a target site for either metolachlor or the oxime ether safeners. Metolachlor and the oxime ether safeners enhanced glutathione levels in grain sorghum seedlings at 12 to 48 hr after imbibition was initiated with oxabetrinil being more stimulatory than metolachlor or CGA-133205. Glutathione reductase activity was also stimulated in safener-treated grain sorghum seedlings. Both safeners slightly enhanced nonenzymatic and enzymatic conjugation of metolachlor with reduced glutathione. Oxabetrinil conjugated enzymatically or nonenzymatically with reduced glutathione at a slow rate, but CGA-133205 did not. These data suggest that during the early stages of seed germination and seedling development of grain sorghum, safeners can enhance the detoxication of metolachlor by enhancing glutathione levels and enzymatic and nonenzymatic conjugation of metolachlor with glutathione. It appears that oxabetrinil and CGA-133205 are conferring protection to grain sorghum by increasing the rate of metolachlor metabolism.
Ph. D.

The objective of this Ph.D. research was to identify new and novel mechanisms of wild radish (Raphanus raphanistrum L.) resistance to photosystem II (PSII) inhibitors, auxinics, and acetohydroxyacid synthase (AHAS) inhibitors. PSIIinhibitor resistance was demonstrated to be target-site based, and conferred by a Ser264 to Gly substitution of the D1 protein. Auxinic resistance was associated with reduced herbicide translocation to the meristematic regions of resistant wild radish plants. Two new resistance mutations of wild radish AHAS were discovered, including one encoding the globally rare Asp376 to Glu substitution, and another encoding an Ala122 to Tyr substitution, which has never been identified or assessed for resistance in plants previously. Characterization of the frequency and distribution of AHAS resistance mutations in wild radish from the WA wheatbelt revealed that Glu376 was widespread, and that some mutations of AHAS are more common than others. Computer simulation was used to examine the molecular basis of resistance-endowing AHAS target-site mutations. Furthermore, through the computer-aided analysis, residues were identified with the potential to confer resistance upon substitution, but which have not previously been assessed for this possibility. Results from this Ph.D. research demonstrate that diverse, unrelated mechanisms of resistance to PSII inhibitors, auxinics, and AHAS inhibitors have evolved in wild radish of the WA wheatbelt, and that these mechanisms have accumulated in some populations.

A field trial was conducted to study the elements of application timing and herbicide compatibility in the use of Burst, a plant growth regulator, and the effects of these two factors on yield of upland cotton. Eight treatments combined the two factors of timing and tank mix. The results showed no significant difference in yield between treatments.

La toxicité cellulaire potentielle de la sulcotrione 2-(2-chloro-4-(methylsulfonyl)benzoyl)-1,3-cyclohexanedione, un herbicide sélectif tricétonique a été évaluée sur Vicia faba et Allium cepa. La génotoxicité a été étudiée sur une culture hydroponique pour des traitements à différentes concentrations de sulcotrione 10-5, 10-4 et 2.10-4 M pendant 45 h. Nos résultats ont montré que la sulcotrione provoque une augmentation dose-dépendante de la fréquence des micronoyaux dans les cellules méristèmatiques des racines. Elle induit des altérations chromosomiques à la concentration la plus faible (10-5M) mais aussi une baisse de l’indice mitotique, ce qui indique l'effet mutagène puissant de cette molécule. C’est le premier travail montrant une génotoxicité de la sulcotrione. Les signes d’intoxication se manifestent par les perturbations de la croissance foliaire et racinaires accompagnées d’un brunissement des racines traitées de Vicia faba. Sulcotrione, Mikado®, marc de raisin et des mélanges de sulcotrione ou Mikado® et de marc de raisin induisent la mort cellulaire. La présence des herbicides ainsi que celle des cocktails ont entrainé l’installation d’un état de stress oxydant caractérisé par une production accrue d’H2O2. La production de radicaux d’oxygène actif s’accompagne d’une augmentation de la production de MDA et un accroissement de la mort cellulaire. L’ajout de l’extrait de raisin aux herbicides, soit à la sulcotrione ou au Mikado®, modifie l'expression des gènes habituellement associés au stress cellulaire. Les cocktails et les herbicides modifient l’expression des gènes hsp70.1, cat, ubiquitin, APX, CuZnSOD cy et CuZnSOD ch. Des mécanismes de défense, d’induction de gènes associés au stress et de génotoxicité sont discutés
Potential cell toxicity of sulcotrione 2-(2-Chloro-4-(methylsulfonyl)benzoyl)-1,3 cyclohexanedione), a selective triketonic herbicide was evaluated on Vicia faba and Allium cepa . Genotoxicity was studied in hydroponic culture conditions for treatment at different pesticide concentrations 10-5, 10-4 and 2.10-4 M for 45 h. Our results showed that sulcotrione treatments caused a dose dependent increase of micronucleus frequencies in root meristematic cells. Sulcotrione induced chromosomal alterations at the lowest concentration used (10-5M) when incubated for 42 h. We have shown a decrease in mitotic index, indicating a potent mutagenic effect of this element. This is the first report for the genotoxicity of such a sulcotrione herbicide. It induced a growth inhibition in both leaves and roots and a brownish color in treated roots. Sulcotrione, trade mark Mikado®, grape marc and mixtures of sulcotrione or Mikado® and grape marc induce cell death. The herbicides, cocktails of products with sulcotrione, such as adjuvant in commercial product, induced several changes for antioxidant cell state characterized by an overproduction of H2O2. Production of harmful radicals was accompanied by increased production of MDA and increase of the cell death rate. Addition of grape extracts to herbicides, either sulcotrione or Mikado®, had different effects and results in different expression of genes usually associated to cell stress. Mixture of grape marc and herbicides enhanced transcript accumulation for different effects and results in different expression of some stress-related genes like hsp70.1, cat, ubiquitin, APX, CuZnSOD cy et CuZnSOD ch. Mechanisms which could be associated to gene expression, cell defense and genotoxidity are discussed

Five herbicides commonly used for suppression of weed growth in white clover seed crops were tested for toxicity against white clover (Trifolium repens), Rhizobium trifolii and the nitrogen fixing symbiosis formed between these two organisms. Trials were carried out on R.trifolii on solid and in liquid media to determine if growth of this bacterium was affected by the presence of the 5 herbicides. Paraquat and MCPB substantially inhibited bacterial growth on solid medium. Bentazone, fusilade and kerb caused very small zones of growth inhibition of R.trifolii on solid agar at high concentrations. None of the herbicides tested affected growth of R.trifolii in liquid culture. In vitro studies of herbicide toxicity toward white clover were carried out to identify interactions of herbicide activity with rhizobial inoculation and supplied nitrogen, and to attempt to identify the targets of herbicide activity. Nodules grown under in vitro conditions were excised and used for ultrastructural examination. Herbicides were applied to plants grown in vitro at two different stages of plant growth. White clover proved to be very sensitive to all herbicides at the early seedling stage. Three week old plants were more tolerant. Pot experiments in a glasshouse environment indicated the relevance of in vitro experiments of herbicide toxicity against plants and gave information on the effect of soil water levels on herbicide activity. Paraquat was extremely toxic to white clover both in vitro and in pot experiments. Nodulation is affected to some extent directly by this herbicide although dessication of foliage probably has some role in halting activity of the nitrogenise enzyme. MCPB caused severe deformation of root tissue both in vitro and in pot experiments. It must be either contaminated with the active form of this herbicide, MCPA, or is being broken down to the active form by bacterial or chemical action. Bentazone did not damage white clover or nodule activity in a consistent way in vitro. However this herbicide did have a deleterious effect on both plant weight and nodulation when applied to white clover grown in soil, particularly under conditions of low soil moisture. Fusilade showed a direct effect on the activity of nitrogenase in vitro. Fusilade also acted more severely against plants of higher nutritional status, and appeared to affect nodule activity directly rather than affecting nodules via damage to other plant parts. Kerb was very toxic to seedling white clover in vitro although older plants were not as susceptible and were stimulated by high concentration of kerb. In pots white clover was slightly inhibited by kerb at recommended concentration while 10 x this concentration did not cause any inhibition of nodulation or plant growth. Differences in results between in vitro and pot studies of toxicity of these herbicides to white clover appear to be due to the different application methods used. In vitro herbicides were applied to the whole plant while in pot experiments herbicides were foliarly applied, hence more uptake by roots would be expected. Pot experiments indicated that changes in nodulation generally reflected changes in plant growth rather than an independent activity of the herbicide on nodulation.

Concern has been raised that herbicides recently registered for use in warm-season turf to control perennial ryegrass could be dislodged from treated areas and deposited on neighboring cool-season grasses. In a field study, rimsulfuron was applied at 17.5 or 35 g ai/ha to perennial ryegrass in the afternoon; the following morning while dew was still present, a greens mower was driven through the perennial ryegrass and across adjacent creeping bentgrass. Irrigation had no effect on perennial ryegrass control but reduced visible track length and injury of neighboring creeping bentgrass. When treated perennial ryegrass was not irrigated prior to simulated mowing, tire tracks were evident on adjacent creeping bentgrass for up to 30 days. Gibberellic acid at 0.12 kg ai/ha and foliar iron at 1.3 kg ai/ha, applied to creeping bentgrass when tracks first appeared, did not enhance recovery of injured creeping bentgrass. Persistence and stability of [2-pyridine 14C] rimsulfuron on turf foliage was also assessed. Rimsulfuron was absorbed by annual bluegrass and perennial ryegrass equivalently and persisted equally on turf foliage. Water extractable rimsulfuron decreased from 60% at 10 minutes after treatment to 40% at 96 hours after treatment. A substantial amount of stable rimsulfuron persists on turf foliage for up to four days. Results from both studies suggest that when applying rimsulfuron near susceptible bentgrass the lowest effective rate should be used, and irrigation should follow two hours after treatment to prevent nontarget injury.
Master of Science

In situ microcosms of a planktonic community were exposed to the triazine herbicide simazine. Randomly selected sets of microcosms were collected and sampled each week for three weeks (plus Week 0). Samples of ambient water were collected each week for evaluation of enclosure effects. Physical and chemical parameters were measured per microcosm. Simazine was measured at Weeks 0 and 3 only. The following organisms were preserved and quantified: phytoplankton, bacteria, and zooplankton, including ciliates, copepod nauplii, cladocerans and rotifers. Simazine decreased dissolved oxygen and pH, but increased nitrate and ammonia concentrations compared to control microcosms. A temporary decrease in temperature occurred at Week 1. Phytoplankton were differentially affected by simazine. Sensitive taxa included Trachelomonas, Glenodinium, diatoms and several species of relatively minor significance. Dinobryon and miscellaneous coccoids were not significantly affected. Phytoplankton ≥9 um were more affected by simazine than phytoplankton <9 um. Many cells <9 um may be facultative or obligate heterotrophs and not susceptible to simazine. Although data were variable, bacteria were also not affected by phytoplankton changes or simazine. Rotifers were the major zooplankters and the two dominant species, Kellicottia bostoniensis and Keratella cochlearis, were reported to graze exclusively on cells <9 um. Polyarthra vulgaris and Synchaeta pectinata also graze in this size range but are not limited to it. Copepod nauplii/copepodids were present, but adult copepods and cladocerans were rare. The tintinnid ciliate Codonella exhibited a temporary population increase during the study. Zooplankton were not affected by simazine-induced changes in the phytoplankton. Kellicottia bostoniensis was the only zooplankter affected by simazine: it had lesser mortality in higher concentrations of simazine. Possible reasons for this enhanced survival were discussed. The zooplankton (primarily rotifers) appeared to feed more on heterotrophic cells than on autotrophic cells, largely as a function of food size, and may have been more closely associated with the detrital food chain than the autotrophic food chain.
M.S.

Mestrado em Ecologia, Biodiversidade e Gestão de Ecossistemas
As práticas agrícolas têm sido associadas a perdas em larga escala a nível da biodiversidade. No entanto, elementos como as margens dos campos, são con-siderados importantes e com potencial para diminuir os impactes da agricultura ao promover fontes de alimento e refúgio. No entanto, os pesticidas e em parti-cular os herbicidas podem afectar estas áreas e provocar impactes nas comu-nidades que dependem destas estruturas. Devido à sua sensibilidade a pertur-bações, os artrópodes são um grupo ideal para avaliar os impactes de pestici-das nos sistemas agrícolas. Para além disto têm um papel fundamental nas teias tróficas, constituindo a maior fonte de alimento para muitos vertebrados que habitam nestes ambientes, como a espécie de lagartixa Podarcis bocagei. Neste estudo, avaliou-se o efeito da utilização de herbicidas nas comunidades de artrópodes de margens agrícolas, com recurso ao método de captura por armadilha de queda e a um método para estimar rapidamente a biodiversidade, a identificação a um nível taxonómico elevado. O estudo focou-se nas diferen-ças entre margens de campos com e sem herbicidas em duas estações, prima-vera e outono. A abundância, riqueza de grupos e a composição de guildas tróficas foram determinadas, assim como a abundância e tamanho dos artrópo-des presas de Podarcis bocagei, a lagartixa mais comum na área. Relativamente às diferenças encontradas entre os campos, destaca-se a ausência de um padrão negativo provocado pelos herbicidas. Na primavera os parâmetros avaliados foram, geralmente, mais elevados nas margens agrícolas tratadas. No outono o padrão que surgiu foi distinto, com um dos campos não expostos exibindo valores mais elevados para os parâmetros avaliados, sendo as diferenças entre os campos mais ténues. Os resultados parecem indicar que alguns dos campos são mais favoráveis às populações de artrópodes, assim como às populações de lacertídeos. No entanto, em geral o tratamento com herbicidas não foi suficiente para explicar as variações encontradas nas comunidades de artrópodes. Outros factores não avaliados, como a estrutura da paisagem e do habitat e a composição florística podem ter contribuído para as diferenças encontradas.
Since the advent of agricultural intensification that agricultural practices such as pesticide usage have become associated with large scale biodiversity losses. However, semi-natural landscape elements associated, such as field margins, are thought to benefit biodiversity and lessen the damaging effects of agricul-ture by providing sources of food and refuges. Nevertheless, Pesticides, and herbicides in particular may also affect these areas and consequently impact the communities that depend on these structures. Because of high diversity and sensitivity to disturbance, arthropods are ideal animals to assess impacts of pesticides in these ecosystems. Furthermore, they play essential roles in trophic webs, constituting the major diet components for many vertebrate spe-cies that inhabit these ecosystems, such as the lizard Podarcis bocagei. In this study the effects of herbicides on arthropod communities of field margins were estimated, using pitfall traps and identification to a higher taxonomic level as a rapid assessment method of biodiversity. The study focused on the differ-ences between herbicide treated and non-treated margins in two distinct sea-sons, spring and autumn, being abundance, group richness, guild composition, abundance and size of prey items of Podarcis bocagei, the most common lizard in the area, determined for all fields. Differences were found between fields, but no clear negative effects were evi-denced as a consequence of herbicidal treatment. In spring, margins of ex-posed fields generally exhibited higher values for the assessed parameters, while in autumn, a distinct pattern arose, with fewer differences found between communities. Results seem to indicate that some of the fields may be more favourable to arthropod populations, as well as lacertid populations, but overall, herbicide treatment was not sufficient to explain the variation found in arthropod commu-nities. Other unassessed factors such as landscape and habitat structure and plant community composition could be contributing to the differences found.

The soybean cultivars differentially sensitive to 'Kwangkyo' and 'Hood' are the bipyridylium herbicide paraquat (1,l'-dimethyl-4,4'-bipyridinium ion). This was confirmed by visible injury observations as well as by measurements of desiccation ratings, chlorophyll content, and chlorophyll fluorescence tracings of fully expanded first trifoliolate leaves of these two cultivars after exposure to a wide range of paraquat concentrations. The margin of this intraspecific differential tolerance to paraquat was narrow and the ratio of the paraquat concentrations causing 50% injury to the tolerant Kwangkyo and to the susceptible Hood (approximate tolerance factor) was found to be 10. Paraquat at 1 μM or higher inhibited rapidly the CO₂ fixation capacity of leaf mesophyll cells, isolated enzymatically from both cultivars. This result shows that the differential response does not result from any differences at the site of paraquat action in chloroplast membranes.
Ph. D.

Thesis (Ph. D.)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains vi, 183 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

The advent of new biological technologies requires significant investment in research and development (R&D). The public sector has historically lead initiatives in agricultural R&D, which due to its public goods nature and high investment risk, the private sector has had limited incentive to participate. However, with the consolidation of intellectual property mechanisms in agriculture – such as Plant Breeders Rights and patents – and the increasing debate on the appropriate rigor they ought to entail, the private sector has accounted for a significant share of the R&D expenditure in the past two decades. Given the ease with which seeds can be reproduced, intellectual property rights (IPRs) and the appropriation of benefits from biological innovations remain controversial. This study investigates the implications of IPRs to the distribution of welfare resulting from the development and introduction of herbicide tolerant rice (known commercially as Clearfield Rice) by a multinational firm (BASF) in southern Brazil. We employ the surplus model by Alston, Norton and Pardey (1995) to estimate the economic surplus accruing to rice producers and the innovator and find that under the current IPR system, under which the Plant Variety Protection Law does not restrain saved seeds' sales, farmers capture the largest share of the economic benefits. We analyze changes to the distribution of welfare under IPR enforcement and find that although both actors would realize larger economic gains, farmers would capture a substantial share of total benefits. Therefore, farmers can gain considerably from IPR-protected biological innovation and at the same time, private investment in research may depend on IPR enforcement that allows sizeable appropriation of economic gains.
L'avènement des nouvelles technologies biologiques exige des investissements importants en recherche et développement (R&D). Le secteur public a historiquement dirigé les initiatives de R&D agricole, qui en raison de son caractère de bien public caracteristique comme un bien public et le risque d'investissement élevé, le secteur privé a eu peu d'incitation à participer. Néanmoins, avec l'affermissement des mécanismes de la propriété intellectuelle dans l'agriculture – tels que Plant Breeders Rights et des brevets – ainsi que le débat croissant sur la rigueur qu'elles possèdent, le secteur privé a été responsable pour une portion significative des dépenses en R&D durant les deux dernières décennies. Étant donné la facilité avec laquelle les graines peuvent être reproduites, les droits de la propriété intellectuelle (DPIs) et l'appropriation des avantages des innovations biologiques est toujours un sujet à controverse. Cette étude porte sur les implications des DPIs sur la distribution de bien être à la suite du développement et introduction d'un espèce de riz tolérant aux herbicides (commercialisé sous le nom Clearfield Rice) par une firme multinational (BASF) dans le sud du Brésil. Nous utilisons le model excédentaire par Alston, Norton and Pardey (1995) pour estimer le surplus économique revenant aux producteurs de riz et à l'innovateur. Nous avons trouvé qu'avec le system des DPI actuel, sous lequel la loi de protection des variétés végétales ne limite pas la vente des graines sauvegardées, ce sont les producteurs qui reçoivent la plus grande partie des avantages économiques. Nous analysons les changements à la distribution de bien être dans l'application des DPIs et nous trouvons que même si les innovateurs et les producteurs réalisent des bénéfices économiques, ce sont les producteurs qui recueillent une portion significative des avantages totaux. Par conséquent, les producteurs peuvent bénéficier de l'innovation biologique protégé par les DPIs. En même temps, l'investissement privé en recherche peut dépendre sur l'application des DPIs qui permettent l'appropriation significative des gains économiques.

Breeding herbicide-tolerant cultivars is a means of extending herbicide utilization. In 1983 and 1984, 20 soybean [Glycine max (L. Merr] cultivars were screened for their reactions to the following herbicides: metribuzin 4-amino-6-(tert)-butyl-3-(methylthio)-astriazin-5-(4H)-one]; vernolate (S-propyl dipropylthiocarbamate); and fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl) aniline]. Each herbicide was applied at the recommended rate X, 2X, and 4X in 1983. An 8X rate was added in 1984. The recommended rates (X) for the herbicides were as follows: metribuzin 0.42, vernolate 2.80, and fluchloralin 1.12 kg/ha. The cultivars were Pella, Pixie, Cumberland, Williams, Essex, Union, Semmes, Tracy, Tracy M; North American Plant Breeders 350, 68225, 420, and 330; Northrup King 8069 and 8047; and Farmers Forage Research 339, 340, 560, and 561. Plant vigor, height, and herbicide injury were the criteria used in estimating herbicide effects. Statistical differences were found among herbicides, rates, and cultivars. Also, there were significant interactions involving herbicides x rates, herbicides x cultivars, rates x cultivars, and herbicides x rates x cultivars. Although not always statistically significant, average vigor ratings decreased with increased herbicide application rate. Pronounced differences in the study results for the two years, likely reflecting rainfall patterns, were evidence of uncontrolled variability. However, a small number of the cultivars exhibited herbicide tolerance.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Devido ao uso frequente do glyphosate na agricultura, o capim-amargoso (Digitaria insularis) tornou-se uma das plantas daninhas mais problemáticas no Brasil, por adquirir resistência a esse herbicida. Biótipos resistentes em estádios iniciais são facilmente controlados por graminicidas, porém em estádio mais avançado o controle é reduzido. O herbicida clethodim é um graminicida com alta eficiência, portanto, verificar o controle de biótipos resistentes ao glyphosate em diferentes estádios, com o uso isolado de clethodim e em mistura com o glyphosate é fundamental para auxiliar no manejo desta invasora. Assim o presente trabalho teve como objetivo avaliar o desempenho de glyphosate, clethodim e glyphosate + clethodim, em biótipo de D. insularis resistente e suscetível. O ensaio foi realizado em casa de vegetação, inteiramente casualizado, com quatro repetições e repetido em duas épocas do ano. As aplicações foram realizadas em estádio inicial (15 – 20 cm) e em florescimento. Avaliou-se o controle aos 21 dias e o peso da biomassa seca. Para a mistura dos produtos, foi verificada a interação entre os herbicidas: efeito sinérgico, antagônico ou aditivo. No ensaio com plantas em estádio inicial, avaliou-se a concentração de lipídeos na biomassa seca. De forma geral, a aplicação de clethodim aplicado isoladamente controlou o biótipo resistente em estádio inicial, porém em florescimento a eficácia foi reduzida. A mistura mostrou-se eficiente para controle de biótipo resistente em estádio inicial e em florescimento. Considerando as avaliações visuais de controle, a interação entre glyphosate e clethodim apresentou efeito sinérgico para doses intermediárias e aditivo para as maiores doses considerando o estádio inicial; em plantas florescidas, predominaram os efeitos aditivos para todas as doses. Para massa seca, a mistura teve interação sinérgica em todas as doses e estádios avaliados. As menores doses dos dois herbicidas reduziram os teores de lipídeos.
Due to frequent use of glyphosate in agriculture, sourgrass (Digitaria insularis) has become one of the most problematic weeds in Brazil for purchase resistance to this herbicide. Resistant biotypes in initial stages are easily controlled by graminicides, but in a more advanced stage the control is reduced. The herbicide clethodim is a graminicide with high efficiency, therefore, to check the control of resistant biotypes of glyphosate in different stages, with the isolated use of clethodim and in mixture with the glyphosate is fundamental to assist in the management of this weed. Thus the experiment was aimed at evaluate the action of glyphosate, clethodim and glyphosate + clethodim, in a resistant and susceptible biotype of D. insularis. The experiment was carried out in a greenhouse, completely randomized, with four replications and repeated at two times of the year. The applications were performed in the initial stage (15 - 20 cm) and flowering. Plants were evaluated at 21 days after application (DAA) and dry biomass weight. For the mixture of products, the interaction between the herbicides was also verified: synergistic, antagonistic or additive effect. In the experiment with plants at the initial stage, was evaluated the lipid concentration in the dry biomass. In general, the application of clethodim applied alone controlled the resistant biotype at the initial stage, but in flowering the efficiency was reduced. The mixture showed to be efficient for control of resistant biotype in initial and flowering stages. Considering the visual evaluations of control, the interaction between glyphosate and clethodim showed synergic effect for intermediate doses and additive for the highest doses considering the initial stage; in flowered plants, with the additive effects predominating for all as doses, the additive effect prevailed for all doses. For dry mass, the mixture had synergistic interaction at all doses and evaluated stages. Lower doses of both herbicides reduced lipid levels.

A three year field study was undertaken to assess the influence of water table management, namely subsurface irrigation and controlled drainage, on the movement of pesticides through the soil profile into ground water. The herbicides under investigation were prometryn on an organic soil, and metolachlor on a sandy soil. Both soil and groundwater were collected and analyzed. The results presented are those obtained in the first two years of the project.
In the organic soil, herbicide leaching was greatly reduced due to the management of the water table. The pesticide remained higher in the soil profile, preventing leaching to the drains and allowing degradation.
The opposite effect appeared to have occurred in the sandy soil. The higher water table resulting from subsurface irrigation may have induced the leaching of the contaminant into lower soil levels and into the ground water. The high water solubility of the herbicide metolachlor, in conjunction with low microbial activity, may have played a role in this phenomenon.

La producció de pinya tropical és una activitat econòmica important a Costa Rica, l’àrea de cultiu de la qual ha augmentat significativament en les dues darreres dècades, i amb una significativa generació de residus agroindustrials i ús intensiu de plaguicides com els herbicides bromacil i diuron. Tots dos han estat detectats en aigües superficials i subterrànies, causant problemes ambientals, de salut i econòmics, malgrat que hi ha poca informació sobre el seu destí ambiental en sòls tropicals. La transformació de residus agroindustrials en biocarbó (biochar) mitjançant piròlisi i la seva adició al sòl com a esmena han estat proposats com una pràctica útil per a la gestió de residus que permet la millora de la qualitat del sòl, el segrestament de carboni i una possible mitigació de la mobilitat de plaguicides. L’objectiu de la tesi fou avaluar els beneficis i eventuals efectes no desitjats de l’adició de biocarbó a un sòl costa-riqueny cultivat amb pinya en combinació amb bromacil o diuron, considerant tant els seus efectes en el destí i eficiència com els ecotoxicològics. Els materials carbonitzats (MC) s’obtingueren per piròlisi a 300 o 600 ºC durant una hora, utilitzant com a materials de partida rostoll de pinya tropical (PS), “”pinzote”” de palmera d’oli (PF) i l’endocarp del fruit de café (cascarilla) (CH), que es van caracteritzar fisicoquímicament i es van aplicar al sòl a dosis d’aplicació de 10 i 20 t ha-1. S’avaluà la sorció, la degradació i la biodegradació dels plaguicides en condicions de laboratori, permetent la predicció del seu risc ambiental amb l’índex de classificació d’impacte de plaguicides. Addicionalment, es van avaluar efectes en l’emergència i creixement de d’enciam (Lactuca sativa), el desenvolupament d’invertebrats (el col·lèmbol Folsomia candid i l’enquitreid Enchytraeus crypticus) i la diversitat funcional de la comunitat dels microorganisms (MicrorespTM) per a provar possibles efectes dels MC en l’eficiència dels herbicides i en organismes terrestres no diana. Els MC a 300 ºC es classificaren com a materials torrefactes (MT) i a 600 ºC com a biocarbons (B). Els biocarbons presentaren major superfície específica, contingut de carboni fixe i pH que els MT, alhora que els PS-B i PF-B tenien major abundància de grups oxigenats superficials que CH-B i que tots els MT. Es va demostrar una sorció dèbil al sòl en tots dos plaguicides, fet que suggereix una elevada mobilitat, i la degradació i biodegradació del bromacil fou limitada en comparació al diruon. L’adició de biocarbó incrementà la persistència del bromacil, i els PS-MT i PF-MT la sorció del diuron. No obstant, això no va canviar la mobilitat i toxicitat aquàtica predites pels pesticides. L’adició de MC no reduí l’eficiència dels herbicides, però augmentà l’emergència sense incrementar el creixement. L’aplicació d’herbicides no causà efectes tòxics en col·lèmbols o enquitreids, sinó que promogué la reproducció sense afectar la supervivència. S’observà una evitació generalitzada de les barreges sòl-MC en enquitreids contrària a la preferència dominant en col·lèmbols, independentment de la presència d’herbicides. Finalment, no aparegueren canvis en la diversitat funcional microbiana amb l’adició d’herbicides o MC, llevat de l’increment en la taxa de consum d’alguns substrats en algunes barreges sòl-MC tractades amb diuron. En conclusió, l’adició de MC no canvià l’eficiència dels herbicides ni el seu destí en l’Ultisol tropical argilós estudiat. Sota la gestió habitual del cultiu de la pinya a la regió nord de Costa Rica, tots dos herbicides presentaren un elevat risc ambiental per a aigües superficials i subterrànies, i malgrat que l’adició de MC no ho va mitigar, no van causar efectes negatius sinó una millora del sòl com a hàbitat per a invertebrats edàfics.
La producción de piña es una actividad económica importante en Costa Rica que ha aumentado significativamente su área cultivada en las dos últimas décadas, con una alta generación de residuos agroindustriales y un uso intensivo de plaguicidas, incluidos los herbicidas bromacil y diurón. Ambos se han detectado en aguas superficiales y subterráneas, lo que ha causado problemas ambientales, de salud y económicos, aunque aún existe poca información sobre su destino ambiental en los suelos tropicales. La transformación de residuos agroindustriales en biocarbón (biochar) mediante pirólisis y su adición al suelo como enmienda, se ha propuesto como una práctica útil de gestión de residuos capaz de mejorar la calidad del suelo, el secuestro de carbono y que podría mitigar la movilidad de los plaguicidas. El objetivo de la tesis fue evaluar los beneficios y eventuales efectos no deseados de la adición de biocarbón a un suelo costarricense cultivado con piña en combinación con bromacil o diuron, considerando tanto sus efectos ecotoxicológicos como en su destino y eficiencia. Los materiales carbonizados (MC) se obtuvieron pirolizando a 300 o 600 °C durante una hora rastrojo de piña (PS), pinzote de palma aceitera (PF) y cascarilla de café (CH), se caracterizaron física y químicamente y se mezclaron con suelo en dosis de aplicación equivalentes a 10 y 20 t ha-1. Se evaluaron la sorción, la degradación y la biodegradación de ambos plaguicidas en condiciones de laboratorio con lo que se predijo su riesgo ambiental con el Índice de Clasificación de Impacto de Plaguicidas. Además, se midió la emergencia y el crecimiento de la lechuga (Lactuca sativa), el desarrollo de invertebrados (colémbolo Folsomia candida; enquitréido Enchytraeus crypticus) y la diversidad funcional de los microorganismos (Microresp™) para probar los efectos de los MC en la eficiencia de los herbicidas y sobre organismos terrestres no diana. Los MC a 300 °C se clasificaron como materiales torrefactos (MT) y a 600 °C como biocarbones (B). Los biocarbones mostraron mayor superficie específica, contenido de carbono fijo y pH que los MT, mientras que los PS-B y PF-B presentaron mayor abundancia de grupos funcionales oxigenados superficiales que el CH-B y que todos los MT. Se observó una sorción débil de ambos plaguicidas en el suelo, lo que sugiere una alta movilidad, mientras que la degradación y biodegradación de bromacil fue limitada comparada con el diurón. La adición de biocarbón aumentó la persistencia del bromacil, mientras que los PS-MT y PF-MT aumentaron la sorción del diurón. No obstante, la movilidad y la toxicidad acuática predichas de los herbicidas no se afectaron. La adición de MC no redujo la eficiencia de los herbicidas, pero aumentó la emergencia sin mejorar el crecimiento. La aplicación de herbicidas no tuvo efectos tóxicos sobre colémbolos o enquitréidos pues promovió su reproducción sin afectar la supervivencia. Hubo una evitación generalizada de los enquitréidos de las mezclas suelo-MC opuesta a la preferencia general de los colémbolos, independientemente de la presencia de herbicidas. Finalmente, no se demostraron cambios en la diversidad funcional microbiana por la adición de herbicidas o MC, y solo se observó un aumento en la tasa de consumo de algunos sustratos en algunas mezclas suelo-MC tratados con diurón. En conclusión, la adición de MC no cambió la eficiencia de los herbicidas ni su destino en el Ultisol tropical arcilloso estudiado. Bajo la gestión habitual del cultivo de la piña en la Región Norte de Costa Rica, ambos herbicidas presentaron un elevado riesgo ambiental para aguas superficiales y subterráneas, y pese a que la adición de MC no le mitigar, no causaron efectos negativos sino una mejora del suelo como hábitat para invertebrados edáficos.
Pineapple production is an important economic activity in Costa Rica as shown by the increase in its cropped area in the last two decades. It involves a high generation of agro-wastes as well as an intensive application of pesticides, including the herbicides bromacil, and diuron. Their use is associated with problems of environmental, health and economic concern, because it has been detected in both surface water and groundwater. However, there is still scarce information about the environmental fate of these herbicides in tropical soils. The transformation of this agro-waste surplus by pyrolysis into biochar, a carbonaceous material, followed by its addition to soil as an amendment, has been suggested as a useful waste management practice. This is because it may improve the soil quality and carbon sequestration and potentially mitigate the mobility of pesticides. The aim of this thesis was to evaluate the benefits and unexpected effects of biochar addition to a Costa Rican agricultural soil cropped to pineapple, concurrently considering the effects on bromacil and diuron fate and efficiency as well as non-target soil ecotoxicological effects. For this purpose, pineapple stubble (PS), oil palm fiber (PF) and coffee hulls (CH) were pyrolyzed at 300 or 600 °C for one hour and then physically and chemically characterized. Mixtures of the charred materials (CM) with soil were prepared at application rates equivalent to 10 and 20 t ha-1. Sorption, degradation, and biodegradation of both pesticides were evaluated in the laboratory, and the results were used to predict their environmental risk with the Pesticide Impact Rating Index. In addition, lettuce emergence and growth (Lactuca sativa), invertebrates performance (collembolan Folsomia candida; enchytraeid Enchytraeus crypticus), and microorganism functional diversity (Microresp™) were used to test the effects of CM on the herbicides’ efficiency and on the non-target soil biological groups. CM pyrolyzed at 300 °C were classified as torrefied materials (TM), while those pyrolized at 600 °C were classified as biochars (B). Biochars showed higher specific surface area, fixed carbon content and pH values than TM, while PS-B and PF-B presented a higher abundance of surface oxygenated chemical groups than CH-B and all the TM. A weak sorption of both herbicides to soil was observed suggesting a high mobility, while the degradation and biodegradation of bromacil was more limited compared to that of diuron. The addition of biochars increased the persistence of bromacil, while PS-TM and PF-TM increased the sorption of diuron. Despite that, the predicted mobility and aquatic toxicity of the herbicides were unaffected. The addition of CM did not reduce herbicide efficiency but increased seedling emergence without improving growth. The adding of herbicides had no toxic effects on collembolans and enchytraeids as it promoted their reproduction without affecting survival. A generalized avoidance of CM-mixtures by enchytraeids was observed as opposed to the general preference shown in collembolans, irrespective of the supplementation or not of herbicides. Finally, no changes in the microbial functional diversity by the sole addition of herbicides or CM were demonstrated, and a significant increase in the consumption rate of some substrates was observed only in some diuron-treated CM-mixtures. In summary, the addition of CM did not change the efficiency of the herbicides nor their fate in a tropical clay Ultisol. Under pineapple cropping conditions of the northern region of Costa Rica, bromacil and diuron presented a high estimated environmental risk to surface water and groundwater, and the addition of CM did not change this risk. Simultaneously, no negative effects to the soil ecosystem were observed, but there was an improvement in soil as a habitat for some soil invertebrates.

Field, greenhouse and laboratory experiments were implemented to investigate the effects of auxin herbicides on growth and yield of cotton in glyphosate based systems. Field experiments evaluated the effect of rate and timing of dicamba or 2,4-D exposure when applied in glyphosate-resistant cotton. Increasing rates of either dicamba or 2,4-D resulted in increased injury and yield reductions. Initial injury symptomology was similar for cotton exposed at vegetative and reproductive stages. When cotton was exposed to auxin herbicides during vegetative growth, injury increased with time, while foliar injury during reproductive growth was stagnant and often decreased with time. Subsequently, the strongest correlations to yield loss and injury were from later evaluations of vegetative timings. Recovery from injury due to auxin herbicide exposure was dependent upon favorable environmental conditions; however, recovery was often superficial and masked significant yield loss.

Greenhouse studies evaluated the impact of the diglycolamine dicamba salt on the movement of 14C radio-labeled potassium salt glyphosate in barnyardgrass and johnsongrass. Increasing glyphosate rate increased total absorption of glyphosate in both species. Total absorption of glyphosate was not impacted by the presence of dicamba, for either johnsongrass or barnyardgrass. Dicamba did not consistently alter the translocation of glyphosate in johnsongrass; however, dicamba did reduce glyphosate translocation in barnyardgrass. Total amount of translocated glyphosate was 2.6 to 4.6% and 3.8 to 6.8% of applied in barnyardgrass and johnsongrass, respectively. Reduced translocation in barnyardgrass was a result of increased glyphosate accumulation in the distal portion of the treated leaf. Increasing the rate of glyphosate did overcome the dicamba induced antagonism; however, altered translocation of glyphosate has been documented to be a precursor to herbicide resistance.

This research focused on the characterization of organosilicone surfactants and their effects on sulfonylurea herbicide activity. The project included efficacy tests, rainfastness studies in the greenhouse, radiotracer studies on herbicide uptake, fluorescent dye studies on surface deposition, and various measurements of physico-chemical properties. In measuring physico-chemical properties, a logistic dose response relationship was found between adjuvant concentration and contact angle on parafilm. An AsymSigR relationship existed between adjuvant concentration and surface tension for all the adjuvants. The organosilicones, Silwet L-77, Silwet 408, and Sylgard 309, and Kinetic (a blend of an organosilicone with a nonionic surfactant) gave equilibrium surface tension values around 20 dyne/cm and showed great spreading ability on the foliage of velvetleaf. With the conventional adjuvants, Agri-Dex, methylated soybean oil, Rigo oil concentration, and X-77, and Dyne-Amic (a blend of an organosilicone with a crop oil concentrate), surface tension was rarely below 28 dyne/cm and spreading ability was limited on velvetleaf. In addition, the organosilicone surfactant and Kinetic also lowered dynamic surface tension, which may improve droplet retention on leaf surfaces. The differences in physico-chemical properties between Kinetic and Dyne-Amic confirmed that carefully electing a co-adjuvant for an organosilicone blend is critical to avoid antagonism with trisiloxane molecules and retain the unique physico-chemical properties of organosilicone in the blends. Studies involving structurally-related organosilicones showed that the end structure in the trisiloxane hydrophilic group has little or no effect on surface tension, contact angle, spread pattern, herbicide uptake and translocation, and efficacy of primisulfuron on velvetleaf. It may be suggested that there is not a strict requirement to purify the end structure during the synthesis process, which is time consuming and expensive. When 14C-primisulfuron was combined with organosilicones or the blends, the uptake of 14C at 1 or 2 h after herbicide application was significantly higher than when combined with conventional adjuvants in velvetleaf. In the greenhouse, organosilicone surfactants greatly increased the rainfastness of primisulfuron in velvetleaf. The effect was immediate and dramatic, even when simulated rainfall was applied 0.25 h after treatment. In addition, herbicide efficacy on marginally susceptible weed species, velvetleaf and barnyardgrass, was significantly increased. A very complicated relationship exists between herbicides and adjuvants. The enhancement effects of adjuvants are often herbicide specific, weed species specific, and even environment specific. No one type of adjuvant functions well in all circumstances. Therefore, there is a need to understand the properties and functions of each class of adjuvants and locate the 'right' niche for each individual adjuvant.
Ph. D.

Industrial hemp (Cannabis sativa) is an old crop being reintroduced into certain states; thus, very little information is known about growing the crop domestically. Two field experiments were established in Bowling Green, KY to evaluate various nitrogen fertilizer rates and timing applications to examine the effects on growth and yield of industrial hemp (Cannabis sativa). Each experiment was sprayed with 1.12 a.i. ha-1 pendimethalin on half of each plot as a pre – emergent herbicide. Hemp was planted at a rate of 43 kg/ ha into a conventionally tilled silt loam soil. Nitrogen rates studied were a control, 79, 157, and 236 kg N/ ha in the first experiment. In the second experiment, 157 kg N/ ha was applied at three timings along with a control. The three timings were: at establishment, side-dressed, and a split application of 78 kg at establishment and 78 kg side dressed. Plots were 6 m x 4.5 m and replicated 4 times for each experiment. Data collected included stand counts 34 days after planting (DAP), plant heights at 34 and 55 DAP, and stand counts, plant heights, fresh biomass, dried biomass, seed yield, and fiber yield at harvest (89 DAP) for both experiments. Increased fertilizer rates increased fresh and dried biomass which correlated with increased fiber yields. Different fertilizer timings had no effect on seed, biomass, or fiber yields. Herbicide had an early effect on stand counts and plant height in both experiments (

La contamination simultanée des écosystèmes aquatiques par des polluants et des nutriments est un problème majeur dont les effets sur les macrophytes sont encore méconnus. L'objectif de cette thèse était d'étudier les effets de deux types de polluants : herbicides et éléments trace métalliques (ETM), en combinaison avec des ressources variables (azote, phosphore, ou carbone) sur Myriophyllum spicatum, en utilisant des paramètres provenant de l'écologie chimique et de l'écotoxicologie. Les tests ont montré des effets contrastés des herbicides sur la plante, mais pas d'effet des ETM. Dans tous les cas, les modifications de ressources (nitrate, ratio N:P ou saccharose) ont induit des effets importants sur la physiologie et la stœchiométrie de la plante, pouvant altérer ses réponses à un stress supplémentaire comme les polluants. Ces résultats suggèrent qu'un déséquilibre des ressources en présence de polluants pourrait modifier leurs effets sur les macrophytes, et soulignent également la nécessité d'ajouter des paramètres plus informatifs dans les tests afin de répondre aux enjeux du stress multiple et améliorer l'évaluation du risque environnemental
Simultaneous contamination of aquatic ecosystems by pollutants and nutrients is a major problem whose effects on macrophytes are still unknown. The objective of this thesis was to study the effects of different pollutants, herbicides and trace metal elements (TME), in combination with varying resource availability (nitrogen, phosphorus, or carbon) on Myriophyllum spicatum, using parameters from chemical ecology and ecotoxicology. Tests showed contrasting effects of herbicides, but no effects of the TME. In all cases, resource modifications (nitrate, N:P ratio or sucrose) induced significant effects on the physiology and stoichiometry of the plant, which might alter its response to additional stress like pollutants. These results suggest that an imbalance of resources in the presence of pollutants may lead to unforeseen changes in the combined effects on macrophytes, and also highlight the need to add more informative parameters in tests to meet the challenges of multiple stress and improve environmental risk assessment

The aim of this work was to study the effect of the herbicide, 2,4-D on a mono- cot (Lolium temulentum Linn.) and a dicot (Raphanus sativus Linn.) in relation to drought stress, in order to elucidate if the combined treatments altered the survival of the plants. Herbicide effects were investigated on a number of plant developmental stages; germination, seedling growth, mature leaves and root function, and were combined with various water stress regimes.2,4-D did not alter the germination percentage in either species when applied singly or with polyethylene glycol (PEG) induce water stress. However, rate of seedling emergence and accumulation of chlorophyll, protein and proline were inhibited. Foliar application of 2,4-D at selective concentrations showed that in addition to induced growth distortion the herbicide reduced the survivial capacity of radish but enhanced that of rye grass to later drought stress. Analysis of the content of proline (a stress metabolite) in both species indicated that the accumulation of this compound was reduced in radish but enhanced in rye grass. In contrast, when 2,4-,VJ)&^Dlapplied via the roots, from water culture, the selectivity of effect was lost since proline accumulation was reduced in both species. Use of (^14)C-2,4-D showed that the herbicide remained in the roots when applied in water culture and that since a major response was seen in the roots this implied that some signalling was occuring between the two organs. From the results it would appear that the use of low doses of herbicides such as 2,4-D may be valuable in protecting certain plants from drought stress, whilst the susceptability of other plants could be increased hence making the herbicide more effective at low concentrations.

Triasulfuron (3-(6-methoxy-4-methyl-1,3,5-triazin-2-yl)-1-[2-(2- chloroethoxy)-phenylsulfonyl)-urea} is a new pre- and post-emergence herbicide developed for the control of broad-leaved_'Teeds and some grasses in small grain cereals at rates of 10-20gha . Oilseed rape, pea, broad bean, Senecio vulgaris, Veronica persica, Lolium renne, Poa annua, Poa trivialis and prates were severely a ed 5y pre-emergence and post-emergence applications of triasulfuron but wheat and barley were much more resistant. The development of injury symptoms was generally slow and was characterized by an initial growth retardation followed by chlorosis and necrosis with death occuring 3-4 weeks after application. The herbicide had a flat dose-response curve throughout the investigations. Wheat and barley showed greater tolerance to post-emergence than to pre-emergence applications. Pre-emergence applications of triasulfuron reduced tiller numbers in barley and wheat but application of the herbicide at the 2-3 leaf stage stimulated the outgrowth of tiller buds but this effect was temporary and was not the result of visible physical damage to the shoot meristem. There was no intra-specific variability between cultivars of wheat and barley. Grain yield and other yield components of spring barley were not affected by post-emergence treatments of triasulfuron. Triasulfuron had high activity through the soil and both the roots and subterranean shoots of developing seedlings absorbed the herbicide from the soil. The bioactivity and mobility of the herbicide down the soil profile was inversely related to the organic matter content of the soil. The amount and frequency of rainfall directly influenced the rate of leaching of the herbicide down the soil profile. Comparisons of the rates of disappearance of triasulfuron in autoclaved and non-autoclaved soils suggested the involvement of a biglogical degragation pathway. Triasulfuron disappeared faster at 30 °C than at 10 °C and higher moisture levels enhanced the rate of breakdown. Studies on the mode of action of triasulfuron indicated that the herbicide acts by inhibiting cell division in susceptible plants. Evidence suggested that the inhibition occurred during interphase rather than during the mitotic sequence. The addition of a 1: 1 mixture of isoleucine and valine to the treatment solution prevented the inhibition of cell division at the root tips of broad bean.

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.

The effects of several preemergence herbicides at various rates were tested on bearing Redblush' grapefruit trees and non-bearing Navel orange trees. Some of the preemergence herbicides caused foliar injury symptoms on the trees including Hyvar X Diuron, and Krovar I although they did not cause significant yield reductions in the short time period of this experiment. Several herbicides including Solicam, Surflan, and Prowl did not cause foliar injury or reduce yield and provided good weed control for various lengths of time. The Prowl treatments provided the longest period of weed control in the experiment on bearing grapefruit trees.

Objective: Paraquat is a commonly used herbicide worldwide and is a well-documented cause of pulmonary fibrosis in studies of laboratory animals and in humans following high dose exposure (usually accidental or as parasuicide). The respiratory effects of long-term, low dose paraquat exposure have not been fully evaluated. We set out to evaluate the possible effects of paraquat spraying among deciduous fruit farm workers in the Western Cape, South Africa. Methods: A cross-sectional study of 126 workers was performed. Administered questionnaires generated information on exposure, respiratory symptoms and confounding variables. Spirometry and gas transfer were measured and chest radiographs performed. Oxygen desaturation on exercise testing was by oximetry during a modified stage one exercise test. Results: No association was found between long-term paraquat exposure and reported symptoms, spirometry (FVC, FEVl, FEVl/FVC) and gas transfer (TLco and Kco) or chest radiography. Multivariate analysis showed a significant relationship between measures of long-term paraquat exposure and arterial oxygen desaturation during exercise (p < 0.05). Conclusion: Previous studies have also not shown a significant relationship between measures of paraquat exposure and standard tests of lung function. Arterial oxygen desaturation during exercise represents a more sensitive test. Our findings indicate that working with paraquat under usual field conditions for a long period is associated with abnormal exercise physiology in a dose dependant fashion.

Orientador: Caio Antonio Carbonari
Banca: Edivaldo Domingues Velini
Banca: Natália Corniani
Resumo: O herbicida nicosulfuron se destaca entre os principais utilizados em pós-emergência na cultura do milho. Dentre as tecnologias disponíveis no mercado, alguns híbridos podem ser considerados tolerantes ao nicosulfuron, e essa sensibilidade diferencial está relacionada com o ambiente, o estádio de desenvolvimento da planta e a dose de herbicida utilizada. A seletividade de herbicidas é geralmente determinada em função da fitointoxicação e do efeito do produto nas características morfológicas e fisiológicas das plantas. De modo que o objetivo do trabalho foi determinar a sensibilidade de híbridos de milho ao herbicida nicosulfuron por meio de marcadores bioquímicos. O primeiro experimento foi conduzido em casa-de-vegetação com delineamento experimental inteiramente casualizado com 4 repetições em esquema fatorial 4 x 2 (híbridos x doses), o herbicida foi aplicado nas doses 0 e 120 g i.a. ha-1 quando as plantas se encontravam no estádio fenológico V3. Foram realizadas avaliações da taxa de transporte de elétrons (ETR), fitointoxicação e altura aos 1, 3, 7 e 14 dias após a aplicação (DAA). Aos 14 DAA as plantas foram coletadas para determinação da massa seca. Dentre os híbridos utilizados selecionou-se o mais sensível e o mais tolerante para a realização de análises de determinação dos teores do ácido aminobutírico, e dos aminoácidos valina, leucina e isoleucina, nesses mesmos períodos de avaliação. O segundo experimento foi disposto em delineamento inteiramente casualizado com 5... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Nicosulfuron stands out among the principal post-emergent herbicides used in the maize crop. Among the commercial technologies available, there are some hybrids considered tolerant to this molecule and can present a differential sensitivity, process which is related to the environment, growth stage and herbicide dose. The objective of the study was to determine the sensitivity of corn hybrids to the herbicide nicosulfuron by means of biochemical markers. The first experiment was carried out under greenhouse conditions in a completely randomized design with four replications in a factorial scheme 4 x 2 (hybrids x doses). The herbicide was applied at 0 and 120 g a.i. ha-1, when the plants were in the V3 stage. Electron transport rate (ETR), phytointoxication and plant height were evaluated at 1, 3, 7 and 14 days after treatment (DAT). Plants were collected at 14 DAT to determine its dry weight. The most sensitive and tolerant hybrids were selected to determinate the content of 2-aminobutyric acid and valine, leucine and isoleucine amino acids, in the same evaluation period. The second experiment was arranged in a completely randomized design with five replications in a factorial scheme 8 x 2 (hybrids x doses), the nicosulfuron was applied at 0 and 120 g a.i. ha-1. The experiment was conducted in different periods, for V2 and V6 maize growing stage. One day after the herbicide application, the plants were collected to determine the content of nicosulfuron, 2-aminobutyric and quinic acid, as well as valine, leucine and isoleucine amino acids. During the experiment, the ETR was evaluated at 1, 7, 10, 14, 21 and 28 DAT, and the variables plant height and phytointoxication at 7, 14, 21 and 28 DAT. At 7 DAT the chlorophyll content was determined. Plants were collected at 28 DAT to determine the shoot dry weight. In the first experiment, the collection of the plants one day after application was considered the ...
Mestre

Glyphosate based herbicides are among the most widely used herbicides in the world. The purpose of this study was to determine developmental toxicity of glyphosate, the active ingredient in the common herbicide Roundup, on developing chicken embryos. Few studies have examined toxic effects of glyphosate alone versus the full compound formulations of Roundup, which include adjuvants and surfactants. Adjutants and surfactants are added to aid in solubility and absorption of glyphosate. In this study chicken embryos were exposed at the air cell on embryonic day 6 to 19.8 or 9.9 mg / Kg egg mass of glyphosate in Roundup or glyphosate only. Chickens treated with 19.8 and 9.9 mg / Kg glyphosate in Roundup showed significant reduction in survivability compared to glyphosate alone treatments and controls. On embryonic day 18, embryos were sacrificed for evaluation of developmental toxicity using wet embryo mass, dry embryo mass, and yolk mass as indicators. Morphology measurements were taken on liver mass, heart mass, tibiotarsus length and beak length. Embryos treated with 19.8 mg / Kg glyphosate and 9.9 mg / Kg glyphosate in Roundup showed significant reductions in wet and dry embryo mass and yolk mass. Tibiotarsus length in 9.9 mg / Kg glyphosate in Roundup treatments were significantly reduced compared to 9.9 mg / Kg glyphosate treatments. Beak length was significantly reduced in 9.9 mg /Kg glyphosate in Roundup treatments compared to all other groups.

Les mécanismes responsables du transfert de l'herbicide isoproturon dans le sol et vers les eaux captées ont été étudiés. D'abord, l'analyse de la teneur en isoproturon dans l'eau libre du sol prélevée par drainage ou bougie poreuse a démontré son passage précoce dans la solution du sol superficielle. Puis, le même sol limono-argileux a servi à constituer des colonnes modéles placées sous conditions climatiques naturelles. Il est apparu que les événements pluvieux susceptibles de provoquer les migrations importantes qui contaminent les eaux souterraines interviennent au cours du premier mois qui suit le traitement : l'isoproturon,non dégradé, est alors très mobile. Enfin, des études de laboratoire en conditions contrôlées ont permis de démontrer que l'isoproturon est peu fixé en tant que tel par les constituants du sol, mais que certains de ses produits de dégradation, rapidement prépondérants, interagissent plus fortement avec le substrat
Ln order to identify processes that act on herbicide isoproturon transfer in soil and water, several experimental studies were attempted. Ln the field, isoproturon appeared to reach surface soil water early after treatment. Then, the same soil was used to fill lysimeters placed under natural climatic conditions. Rainwater was able to produce large exportations only during the first month after treatment, because isoproturon, not yet fully degraded, was very mobile. Last, experiments under laboratory controlled conditions showed that isoproturon was sorbed only weakly on soil components. On the opposite, some of its degradation products, which rapidly represent the greatest part of residues, were more strongly held to soil

Le glufosinate d’ammonium (GLA) est le principe actif d’un herbicide à large spectre. Son utilisation tend à s’accroître avec le développement des cultures transgéniques résistantes à cet herbicide, entraînant une augmentation de l'exposition des agriculteurs au GLA, à de faibles doses mais sur des périodes prolongées. L’action herbicide du GLA s’effectue par inhibition de la glutamine synthétase (GS) végétale. Cette enzyme, est également présente dans le système nerveux central des mammifères où elle joue un rôle primordial dans l’homéostasie du principal neurotransmetteur excitateur, le glutamate. Dans le cas d’intoxication aiguë chez l’Homme, le GLA induit des convulsions. Au cours de ce travail, nous avons tenté d’établir, sur le modèle souris, l’origine de ces convulsions et les autres conséquences cérébrales du traitement. L’évolution spatio-temporelle de l’activation de la protéine Fos semble attribuer l’origine des convulsions induites par le GLA (75 mg/kg) au gyrus denté. Les crises d’épilepsie induites par le GLA sont suivies de dégénérescence neuronale et d’une réaction microgliale 24 h après l’injection de GLA ainsi que d’une astrogliose à 15 j. Le diazepam arrête les crises d’épilepsie et prévient la neurodégénérescence mais n’empêche par la réaction gliale. Dans la deuxième partie de mes travaux de thèse, nous nous sommes intéressé au GLA en tant qu’herbicide pouvant présenter un risque en termes de santé publique. Nous avons évalué les effets neurotoxiques d’un traitement chronique à faibles doses de GLA. Un tel traitement induit chez les souris un léger déficit d’apprentissage spatial observé dans le test du labyrinthe radiaire. Par ailleurs, l’étude IRM associée à une analyse de texture montre que la structure de l’hippocampe est altérée. Cette altération peut être corrélée avec les changements métaboliques observés tels que l’activation de la GS. Ces résultats plaident en faveur d’un effet neuroactif du GLA.