Memoria para optar al título de Químico / Imidacloprid pertenece a un nuevo tipo de pesticidas llamados neonicotinoides. Estos son pesticidas sistémicos que se distribuyen dentro de las plantas después de ser absorbidos por ellas. Se les utiliza mediante rociado y en recubrimiento de semillas, principalmente para el control de plagas en cultivos como cereales, soja, maíz y muchas frutas y verduras. Desde la introducción de imidacloprid en 1991, el uso de diferentes pesticidas neonicotinoides ha crecido considerablemente, en Chile este pesticida se encuentra entre los 10 más vendidos de acuerdo a reportes del SAG. Debido a su baja lipoficidad y reducida presión de vapor, el imidacloprid es un potencial contaminante de aguas naturales superficiales o subterráneas, ya sea por escorrentía o percolación. Este hecho evidencia la necesidad de establecer la situación ambiental correspondiente mediante el análisis periódico de aguas, lo que a su vez requiere disponer de métodos de análisis adecuados en términos de sensibilidad y selectividad. En esta investigación se desarrolló un método para determinar imidacloprid en aguas, basado en extracción líquido-líquido micro dispersiva (DLLME) y fluorescencia foto-inducida asociada a calibración multivariada. Dado que la eficiencia de la extracción tiene una dependencia multifactorial, ésta fue optimizada mediante superficie de respuesta obteniéndose una recuperación promedio de 61 % (aceptable para las concentraciones del analito evaluadas entre 4 a 14 ng ml -1), utilizando cloroformo-acetonitrilo (extractante-dispersante) en presencia de NaCl y agitación en vortex. La generación de un compuesto fluorescente se logró por irradiación del analito con luz UV a 254 nm, en medio básico, en un sistema batch utilizando un capilar de vidrio. Los espectros de emisión y de excitación-emisión fueron obtenidos mediante espectroscopia de fluorescencia en micro-cubetas de cuarzo en una región amplia de longitudes de onda. El método de cuantificación fue desarrollado utilizando calibración de segundo orden, aplicando mínimos cuadrados parciales desdoblados acoplados a bilinearización residual (U-PLS/RBL) y análisis paralelo de factores (PARAFAC) a matrices de excitación-emisión. Estas herramientas fueron utilizadas para predecir la concentración del analito en presencia de potenciales interferentes (otros pesticidas neonicotiniodes y fipronil). Se analizaron tres grupos de muestras de complejidad creciente, los primeros dos set de validación se realizaron en buffer, el primero sin interferentes y el segundo en presencia de potenciales interferentes, obteniéndose un error de predicción (REP) inferior a 10% y un límite de detección (LOD) igual o inferior a 0,007 μg ml-1. El tercer set de muestras se realizó en presencia de interferentes agregando la etapa de extracción, se compararon estos resultados con los obtenidos mediante el método de referencia HPLC-DAD. Se observó que al agregar la etapa de DLLME se sobre-exige el modelo predictivo de segundo orden debido posiblemente a la co-extracción de otros compuestos no modelados, obteniéndose un error de predicción (REP) de 16% al utilizar U-PLS/RBL y porcentajes de recuperación entre un 50-88%. Este problema se confirmó al analizar un set de muestras reales, en el cual el porcentaje de recuperación obtenido estuvo entre un 27-93%, presentando mayor dificultad las muestras con un alto contenido de materia orgánica o con elevada dureza. Debido a los problemas presentados con DLLME se propuso evaluar un método alternativo de extracción de imidacloprid mediante extracción en fase sólida con columnas de C-18. Se compararon los resultados obtenidos mediante este método con los obtenidos mediante DLLME obteniéndose mejores resultados para la SPE C-18 en cuanto a precisión y recuperación. Posteriormente se analizó nuevamente un set de muestras reales, obteniéndose recuperaciones entre un 64-114% / Imidacloprid belongs to a new type of pesticides called neonicotinoids. These are systemic pesticides which spread within the plants after being absorbed by them. They are used by spraying and seed coating, mainly to control pests in crops such as corn, soybean and many fruits and vegetables. Since the introduction of imidacloprid in 1991, the use of different neonicotinoids pesticides has grown considerably, this pesticide in Chile is among the Top 10 in sales, according to reports from SAG. Due to its low lipophilic and reduced vapor pressure, imidacloprid is a potential contaminant of surface natural waters or groundwater, either by runoff or percolation. This fact highlights the need to establish the appropriate environmental situation through regular analysis of water, which in turn requires the availability of appropriate methods in terms of sensitivity and selectivity. In this research, a method was developed to determine imidacloprid in water, based on dispersive liquid-liquid micro-extraction (DLLME) and photo-induced fluorescence associated with multivariate calibration. Given that the extraction efficiency has a multifactorial dependence, it was optimized through response surface obtaining an average recovery of 61% (acceptable for analyte concentrations evaluated between 4 and 14 ng ml -1), using chloroform-acetonitrile (extractant-dispersant) in the presence of NaCl and vortexing. The generation of a fluorescent compound was achieved by irradiating the analyte with UV light at 254 nm, in a basic medium, in a batch system using a glass capillary. The emission spectra and MEE were obtained through fluorescence spectroscopy, using quartz micro-cuvettes in a wide wavelength region. The quantification method was developed using second-order calibration, applying unfolded partial least squares coupled to residual bilinearization (U-PLS/RBL) and parallel factor analysis (PARAFAC), associated with MEE. These algorithms were used to predict the concentration of the analyte in the presence of potential interferents (fipronil and others neonicotinoids pesticides). Under these conditions, three groups of samples of increasing complexity were analyzed; the first two validation sets were performed in buffer, the first one without interferents and the second in presence of potential interferents, obtaining a error of prediction (REP) under 10% and a limit of detection (LOD) equal or lower than 0.007 μg ml-1. The third set of samples was performed in the presence of interferents, including the extraction stage; these results were compared with those obtained by the reference method HPLC-DAD. It was noted that adding the step of DLLME over-demands the model, possibly due to the co-extraction of other not modeled compounds, yielding 16% as error of prediction (REP) when using U-PLS/ RBL and recovery rates between 50-88 %. This problem was confirmed by analyzing a set of real samples, in which the recovery rate obtained was between 27-93%, being the most difficult samples those with high organic content or high hardness. Due to problems presented with DLLME, it was proposed to conduct an alternative imidacloprid extraction method through solid phase extraction (SPE) using C18 columns. The results obtained by this method were compared with those obtained by DLLME, yielding better results for the C18 SPE for precision and recovery. Subsequently, a set of real samples were analyzed once again, obtaining recoveries between 64-114%

In one study described herein, 20 privately owned structures were treated with a 0.05% application of imidacloprid (Premise 75 WSP) in order to control infestations of subterranean termites. All applications were made at 15 L per 3.05 linear m per 0.30 m of depth. Ten structures were infested with Reticulitermes flavipes (Kollar) and ten structures were infested with Coptotermes formosanus Shiraki. All structures were inspected through 42 months post-treatment. Only one structure infested with R. flavipes required post-treatment action. Six structures infested with C. formosanus required post-treatment action. In another study, efficacy data were gathered on Premise Granules when broadcast over an open field and when utilized as a "spot treatment" for control of subterranean termites infesting structures. Open field grids with active R. flavipes were utilized in this study. Grids measuring 8.53 m x 7.32 m were marked off, in-ground commercial termite monitors were installed, and grids were treated with Premise Granules. Untreated southern yellow pine surface boards were then placed in grids to determine if Premise Granules would suppress foraging and feeding on surface boards. Premise Granules did suppress surface feeding of R. flavipes for 9 months post-treatment, although termites were active throughout the study in in-ground commercial termite monitors within treated grids. In a third study, 10 structures built on monolithic slabs, five received a "spot treatment" with Premise Granules at points of subterranean termite infestation 0.61 m either side of active exterior subterranean termite mud tubes. Structures were inspected through 12 mo post-treatment. Suppression of R. flavipes was sustained for 8 wks in all treatment replications following application of granules, with failures at 8, 12, and 28 weeks post-treatment. A laboratory trial was initiated to simulate field treatments with Premise 75 WP 0.10 % AI imidacloprid for treatments of structures. The focus of this research was to investigate the dissipation and translocation of imidacloprid in urban environments. Treated sandy loam soil was added to 19-L buckets. Four different plant species commonly found in urban environments were planted in buckets. Results in these trials indicate that imidacloprid was soluble and that there is leaching.

Thesis (M.S.)--Villanova University, 2008. / Chemistry Dept. Includes bibliographical references.

Tesis para optar al grado de Magíster en Química / El síndrome de colapso de colmena que afecta a las abejas, principales polinizadores de las plantas, ha escalado hasta convertirse en un problema global. El abandono, sin causa aparente, de colmenares completos con abundancia de comida amenaza de manera alarmante la polinización de cultivos. Estudios recientes relacionan este síndrome con la utilización de pesticidas sistémicos denominados neonicotinoides, los cuales, a pesar de no tener efectos letales a bajos niveles de concentración sobre estos insectos, si presentarían efectos negativos importantes, como por ejemplo la disminución en la capacidad de aprendizaje y la capacidad de forrajeo, además de hacerlas más propensas a adquirir enfermedades, lo que estaría propiciando este fenómeno. Es por esto que la determinación de este tipo de pesticidas, en especial imidacloprid, por ser uno de los más utilizados en el país, es de suma importancia. Estos pesticidas se han encontrado en uno de los productos producidos por las abejas: la miel. Este es un reservorio final de compuestos y contaminantes provenientes de las abejas y refleja su estado metabólico y de salud. Por lo que, es posible obtener información importante sobre la exposición de las abejas a pesticidas al realizar su determinación en miel. Sin embargo, las metodologías comúnmente utilizadas para este fin consumen tiempo y solventes. Es por ello que el diseño de una metodología rápida, con bajo consumo de solventes y con un pre-tratamiento de muestra simple es deseable. La espectroscopia de fluorescencia surge como una alternativa interesante por su sensibilidad y bajo coste, la que además puede ser asociada a procedimientos de análisis multivariado para mejorar su selectividad. En el presente trabajo se presenta un método para la determinación de imidacloprid en muestras de miel basado en la medición de fluorescencia foto-inducida en el tiempo; asociada a resolución multivariada de curvas con mínimos cuadrados alternantes (MCR-ALS). Para la generación del producto fluorescente las muestras fueron irradiadas con luz UV a una longitud de onda de 254 nm. Como etapa previa se realizó un tratamiento de las muestras destinado a disminuir las interferencias, el que contempló una extracción líquido-líquido soportada sobre columnas de tierra de diatomeas y limpieza mediante extracción en fase sólida sobre carbón grafitizado. Una serie de estudios previos sobre la inducción fotoquímica de la fluorescencia de imidacloprid en tampón y en presencia de la matriz obtenida después de este tratamiento, llevada a cabo mediante MCR-ALS, mostró que la formación del producto fluorescente se produce en forma paralela a la ruta principal de foto-degradación del imidacloprid. La ventaja de segundo orden alcanzada con MCR-ALS permitió la determinación de imidacloprid en presencia de interferencias presentes en las muestras, las que también muestran fluorescencia nativa o foto-inducida (compuestos fenólicos y furfurales). La recuperación promedio para un set de muestras de prueba contaminadas con distintas concentraciones de imidacloprid fue de 98%, con un error relativo de predicción del 20% El límite de detección fue de 0,025 ug/g, que es inferior al límite de residuos máximo permitido de imidacloprid en miel por la legislación en la Union Europea (0,050 μg/g). El método se aplicó para la determinación de imidacloprid en muestras de miel unifloral y polifloral recolectadas directamente de los productores, sin que se detectara presencia del pesticida. La recuperación del compuesto desde estas muestras contaminadas a 0,05 ug/g fue cuantitativa

Research was conducted in 2013 and 2014 to evaluate the influence of cotton (Gossypium hirsutum L.) insecticidal seed treatments, planting date, and preemergence herbicides on thrips (Frankliniella fusca) infestations in cotton. Studies included a preemergence and soil texture evaluation on cotton development, an evaluation of thrips infestations, cotton development and yield following application of various preemergence herbicides and insecticidal seed treatments, and a planting date evaluation where different cultivars where planted with exclusion or inclusion of preemergence herbicide use at four different planting dates to determine the effect on thrips infestations, cotton development, and yield.

Memoria para optar al Título Profesión de Ingeniero Agrónomo Mención: Fruticultura / Pseudococcidae (chanchitos blancos) en naranjos, aplicándolo en enero del 2003 con dos sistemas de aplicación; al follaje (80, 100, 120 cc p.c./Hl) con una motopulverizadora y al tronco con una pistola asperjadora (9 y 12 cc p.c./árbol). Estos tratamientos se contrastaron con Clorpirifos aplicado sólo y vs. un programa de control con Clorpirifos aplicado en enero e Imidacloprid 60 días antes de la cosecha (junio/2003). / A new Imidacloprid formulation (Confidor Forte 200 SL) was evaluated against Pseudococcidae (mealybugs) on orange trees; the application was made in January 2003 utilizing two different spray systems: hand spray gun on the foliage using rates of 80, 100, 120 cc c.p/Hl, and a “pistol” (trigger pump-like) sprayer to apply localized on the bark using 9 and 12 cc c.p./tree. These treatments were compared to Chlorpyriphos applied alone and vs. a program including Chlorpyriphos applied in January and Imidacloprid applied 60 days before harvest (June/2003).

The honey bee, Apis mellifera, provides about $15 billion USD in crop value each year in the U.S. alone in the form of pollination services. Since 2006, commercial beekeepers have reported an average annual overwintering loss of about 28.6% of all managed colonies. There are many factors that are thought to contribute to colony loss including bee-specific pests (e.g. the Varroa destructor mite), bee-specific pathogens (e.g. Nosema fungus), modern beekeeping practices, diminished genetic variability, poor queens, climate change, and exposure to agricultural pesticides. While not the single cause of colony loss, the neonicotinoid insecticides elicit sublethal effects to honey bees that could increase their sensitivities to other stressors that affect colony health. Previous studies found that honey bees have differential sensitivities to the neonicotinoid insecticide imidacloprid, which suggest a mechanism of tolerance to the insecticide in certain colonies. In this study, I examined the imidacloprid sensitivity of honey bees collected from different colonies. After determining a range of LC50 values in the tested colonies, I examined the metabolic detoxification activities of honey bees collected from two colonies that represented the highest and lowest LC50 values, between which there was a 36-fold difference in their LC50 values. I discovered that of the three main families of metabolic detoxification enzymes, general esterases, cytochrome P450 monooxygenases, and glutathione S-transferases (GSTs), a reduction of GST activity with diethyl maleate (DEM) significantly increased imidacloprid-mediated mortality to the honey bees. A comparative analysis of GST kinetic activity from imidacloprid-susceptible and -insensitive honey bees revealed a lower bimolecular inhibition rate constant (ki) for imidacloprid-insensitive individuals (5.07 ± 0.098 nmol/min/mg protein) compared to the imidacloprid-sensitive honey bees (17.23 ± 1.235 nmol/min/mg protein). The IC50 of DEM estimated for bees from each colony showed that the imidacloprid-susceptible honey bees possess a higher IC50 (10 μM) than that of the tolerant honey bees (3 μM). These data suggest that the GSTs in the imidacloprid-tolerant honey bees might be a more efficient detoxification mechanism for the conjugation and elimination of imidacloprid, or imidacloprid metabolites, compared to that of imidacloprid-susceptible honey bees. Therefore, I hypothesize that the differences in metabolic detoxification enzyme activities of honey bees collected from different colonies can result in the differential toxicities of honey bees exposed to neonicotinoid insecticides, such as imidacloprid. However, a thorough examination of imidacloprid detoxification in honey bees is warranted to confirm this hypothesis. / Master of Science in Life Sciences

Bumble bees provide valuable pollination services to many agricultural crops and wild flower species. Consequently, evidence that wild populations are in decline has caused widespread concern. Among multiple causal factors, some have singled out neonicotinoid pesticides as potentially a major contributor to these declines. Bumble bees are exposed to neonicotinoids, such as imidacloprid and thiamethoxam, whilst foraging for nectar and pollen from treated crops. For neonicotinoids to cause population decline, the typical residues that bumble bees encounter in the field (defined here as between 1–12 μg kg-1) should be capable of reducing colony success by detrimentally impacting demographically relevant endpoints such as reproduction and worker performance. Whether field-realistic neonicotinoids are capable of causing such effects is yet to be fully established. The overall aim of this thesis was to investigate the effects of field-realistic neonicotinoids on endpoints of demographic importance and improve understanding of the effect mechanisms of neonicotinoids in bumble bees. Laboratory experiments were conducted with Bombus terrestris L. exposed to dietary neonicotinoids up to 98 μg kg-1. Results showed that food consumption and production of brood (eggs and larvae) in queenless B. terrestris microcolonies were significantly reduced by the two highest concentrations of imidacloprid and thiamethoxam tested (39, 98 μg kg-1), but only imidacloprid produced a negative effect when concentrations were in the typical field-realistic range. Imidacloprid’s affect on microcolonies was mirrored in queenright colonies where field-realistic concentrations substantively reduced both feeding and brood production. It was postulated that the detrimental effects of imidacloprid on brood production emerge principally from nutrient limitation imposed by the failure of individuals to feed. Removing imidacloprid from the bees’ diet resulted in the recovery of feeding and brood production in queenright colonies, even when previously exposed to high doses (98 μg kg-1). Investigation into the effect mechanisms of imidacloprid in B. terrestris revealed that cytochrome P450 enzymes are not important for metabolism of the neonicotinoid in adult workers. A transcriptomic analysis indicated B. terrestris exhibit a general stress response to imidacloprid, characterised by the alteration in expression of genes involved in, for example, metabolism and storage of energy. The thesis findings raise further concern about the threat of imidacloprid to wild bumble bees. However, they also suggest that some demographically important endpoints are resilient to imidacloprid as a realistic pulsed exposure, and that bumble bees may be less sensitive to field-realistic concentrations of thiamethoxam. Further research, which is required to fully establish the demographic consequences for bumble bees of exposure to neonicotinoids, can be developed based on the foundation of work presented here.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references. Also available by subscription via World Wide Web.