Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves [224]-254). Also available on the Internet.

In this study, a sensitive high performance thin-layer chromatography method (HPTLC) was developed to detect lipids in microgram (ug) quantities of hemolymph. The effect of age, diurnal rhythms, and flight activity on hemolymph 1,2-diacylglyceride concentrations in male and female Heliothis zea (Boddie) (Lepidoptera: Noctuidae) were quantitated. The HPTLC method involved a two-stage, one dimensional solvent system, 1 ). benzene:ether(diethyl):ethanol:acetic acid, 50:40:2.0:0.2; 2). hexane:heptane: ether (diethyl): acetic acid, 63:18:18:1. The solvent system separated alkanes, steryl ester, mono-, di- and triacylglycerides, free fatty acids and cholesterol. Lipids were detected with a fluorescent reagent, 1 mM 6-p-toludino-2-napthalenesulfonic acid (TNS) in 95% methanol. Detection sensitivities were 50 ng qualitatively and 500 ng quantitatively. Most male and female Heliothis zea flight activity occurred between 17⁰⁰ and 3⁰⁰ EST each day. Male flight activity after the day of eclosion through 6 days was 0.8, 1.0, 7.0, 3.3, 3.8, 2.8 and 4.0 times the flight activity of the females. Females had a unimodal pattern of flight activity between 17⁰⁰ and 19⁰⁰ Males had a bimodal pattern between 17⁰⁰ and 19⁰⁰, but another higher peak of flight activity existed between 20⁰⁰ and 24⁰⁰. The hemolymph of Heliothis zea males and females prior to flight (17⁰⁰) was composed of mainly diacylglycerides (50% w/w), and triacylglycerides (35% w/w). In addition, cholesterol esters (2%) and less than 1% monoacylglycerides and cholesterol were present, but free fatty acids were not detectable ( <0.5 ug/ul). The lipid class, 1,2-diacylglycerides, apparently are used for flight energy. They occured in the highest concentrations in both males and females prior to flight (17⁰⁰) (approximately 32 ug/ul), then decreased steadily throughout flight to approximately 16 ug/ul at 2⁰⁰ when flight activity was reduced or ceased. Males and females appear to have similar 1,2-diacylglyceride concentrations prior to, during and after flight activity. / M.S.

A strategy for the discovery of new insect growth regulators from arid lands plants was developed. Plant genera with a history of toxicity, medicinal use, or incorporation in native american cultures were selected. Forty-five species from twenty-one families were collected, extracted, and tested for biological activity on the large milkweed bug, Oncopeltus fasciatus. Eight extracts were toxic and the extract of Nama hispidum (Hydrophyllaceae) caused nymphs to undergo precocious metamorphosis to an adult. The active component of N. hispidum was precocene II (6,7-dimethoxy-2,2-dimethyl chromene). Nine Nama species, representing four of the five sections in the genus were gathered from Hawaii, California, Nevada, Arizona, New Mexico, and the Dominican Republic. In addition to the insect anti-hormone, precocene II (PII), present in N. hispidum, N. rothrockii contained at least two different insect juvenile hormone mimics, and N. sandwicense contained insect anti-hormone and insect juvenile hormone mimics. Fifth instar larvae of Heliothis zea were used as model insects to distinguish between post-ingestive intoxication and feeding deterrency during exposure to PII. Larvae fed artificial diet with PII were deterred from eating, and had retarded weight gain, growth, and development. Insects grown on diet with PII consumed less food, could not digest the food, or convert ingested food to body mass. in vivo radiotracer studies with the nutrient, ¹⁴C linoleic acid, show a lower rate of transport and incorporation of radioactivity into fat body tissue. A change in the midgut epithelial cells from PII resulted in reduced transport efficiency and retarded larval growth and development. Scanning electron microscopy of the midgut epithelia indicated that cytotoxic damage is induced by PII. Observed changes in the midgut epithelial cells are consistent with a destructive alkylation of cell structures by PII.

No description available.

Thesis (Ph.D.)--Mississippi State University. Department of Entomology and Plant Pathology. / Title from title screen. Includes bibliographical references.

Tesis presentada como parte de los requisitos para optar al Grado de Magíster en Ciencias Agropecuarias, Mención Sanidad Vegetal / En un ensayo de laboratorio se determinó el efecto antialimentario de extractos acuosos de hojas de Schinus molle (L.) y Artemisia absinthium (L.) al 100 y 50% v/v de las concentraciones máximas obtenidas, sobre larvas de tercer estadío de Heliothis zea (Boddie), una plaga importante en maíz para consumo fresco en muchos países. También se evaluó en laboratorio el efecto tóxico de ambos extractos al 100 y 50% v/v, solos y en mezcla con Bacillus thuringiensis Berliner var. kurstaki (Btk) al 50% sobre las larvas. Finalmente, las concentraciones de ambos extractos se aplicaron sobre estilos frescos en un ensayo de campo, donde se evaluó el número de larvas de H. zea y el daño causado en mazorcas frescas a la cosecha en el Cantón Chambo, Provincia de Chimborazo, Ecuador. En los ensayos de laboratorio para los efectos antialimentario e insecticida se usó un diseño aleatorizado, y en el de campo uno en bloques completamente aleatorizado; en este ensayo, además de los tratamientos indicados arriba se usó un testigo sin tratar y un tratamiento estándar (en Ecuador) con el insecticida comercial Nockeo® (tiametoxan + lambdacialotrina). El extracto acuoso de S. molle al 100 y 50% v/v tuvo efecto antialimentario de 45,2 y 48%, respectivamente y el de A. absinthium al 100 y 50% v/v ningún efecto (0%). En el ensayo del efecto insecticida en laboratorio, los extractos de S. molle al 100 y 50% v/v y S. molle en mezcla con Btk al 50% causaron mortalidad de 20, 28 y 44%, respectivamente, al igual que A. absinthium al 100 y 50% v/v y A. absinthium 100% v/v en mezcla con Btk al 50% (24, 40 y 28% de mortalidad, respectivamente) a 15 dda. Los extractos acuosos de hojas de S. molle y A. absinthium solos y en mezcla con Btk no disminuyeron significativamente el daño causado por las larvas de H. zea, pero los extractos de S. molle 100% v/v, S. molle 100% v/v en mezcla con Btk 50% y Btk 100% v/v redujeron significativamente el número promedio de larvas detectadas a la cosecha en 20 mazorcas frescas en el campo, 3,4; 4,8 y 4,4, respectivamente. Estos resultados motivan, previo a pruebas del efecto residual y fotodegradación, y mejoras en técnicas de aplicación en el campo, a continuar con la evaluación de extractos botánicos en mezcla con Btk con el fin de reducir el uso indiscriminado de insecticidas convencionales. / The antifeeding effect of water extracts from Schinus molle (L.) y Artemisia absinthium (L.) were determined in the laboratory at 100 and 50% of the maximum concentrations obtained, on third stage Heliothis zea (Boddie) larvae, an important pest of fresh corn in many countries. The toxic effect on those larvae of both extracts at 100 and 50%, alone and mixed with Bacillus thuringiensis Berliner var. kurstaki (Btk) at 50% were also determined. Finally, the concentrations of both extracts were applied to the fresh ear corn styles in a field trial in Cantón Chambo, Provincia de Chimborazo, Ecuador, were the number of H. zea larvae and the damage caused on fresh corn ears were determined at harvest. In the laboratory test for the antifeeding and insecticide effects a random design was used, and a completely random block design was used in the field trial, were besides the treatments indicated above, an untreated control and a standard treatment (in Ecuador) with the commercial insecticide Nockeo® (tiametoxan + lambdacyalotrin). The S. molle water extract at 100 and 50% v/v had 45.2 and 48% antifeeding effect, respectively, and that from A. absinthium at 100 and 50% v/v had no effect (0%). In the insecticide test in the laboratory, 15 days after application, the water S. molle extracts at 100 and 50% v/v, and S. molle mixed with Btk at 50% caused 20, 28, and 44% mortality, respectively, similarly to A. absinthium at 100 and 50% v/v, and A. absinthium 100% v/v mixed with Btk at 50% (24, 40, and 28% mortality, respectively). The water extracts from S. molle and A. absinthium, singly or mixed with Btk did not decrease significantly the damage caused by H. zea larvae, but the S. molle extract at 100% v/v, and at 100% v/v mixed with Btk at 50% or 100% v/v reduced significantly the average number of larvae detected at harvest on 20 fresh corn ears in the field, 3.4, 4.8, and 4.4, respectively. These results prompt, after tests of residual effect and light degradation, and improvements in the application techniques in the field, to continue evaluating plant extracts mixed with Btk with the goal of reducing the indiscriminate use of conventional insecticides.

Orientador: Arlindo Leal Boiça Júnior / Resumo: A resistência de plantas a insetos pode trazer contribuições significativas para o manejo de Chloridea virescens (Fabricius) e Spodoptera cosmioides (Walker) em algodão. Porém, ainda há poucas informações de genótipos comerciais resistentes a essas pragas e para selecioná-los é preciso, primeiramente, estabelecer uma metodologia de pesquisa confiável, melhor diferenciar para materiais resistentes e suscetíveis. Assim, neste trabalho foram avaliados potenciais fatores capazes de interferir na expressão de resistência de algodoeiro a S. cosmioides e C. virescens e, posteriormente, foi avaliada a influência de diferentes genótipos de algodoeiro sobre o comportamento de alimentação e desenvolvimento biológico de ambas as espécies para selecionar genótipos resistentes. Foi avaliada a influência dos fatores densidade larval, estrutura vegetal e idade da planta, utilizando as cultivares DeltaOpal e FMT 701. Para S. cosmioides, o uso de duas lagartas de 3º ínstar por disco foliar oriundos da parte mediana de plantas de algodoeiro em estádio de florescimento e para C. virescens uma lagarta de 3º ínstar por disco foliar de folhas da parte superior de plantas em estádio de botão floral permitiram melhor discriminação entre as cultivares quanto seus níveis de resistência. Com base nesses resultados, foi avaliada a influência de genótipos comerciais de algodão sobre o comportamento de alimentação e desenvolvimento de ambas as espécies-praga. Em relação a S. cosmioides, foram avaliados as ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Host plant resistance can contribute significantly to the management of Chloridea virescens (Fabricius) and Spodoptera cosmioides (Walker) in cotton. However, there is still little information on commercial genotypes resistant to these pests and to select them we must first establish a reliable research methodology to better distinguish between resistant and susceptible materials. In this work, we evaluated potential factors capable of interfering in the expression of resistance of cotton to S. cosmioides and C. virescens and, subsequently, the influence of different cotton cultivars on the feeding behavior and biological development of both species was evaluated, aiming select resistant cultivars. The influence of larval density, plant structure and plant phenological stages was evaluated using the DeltaOpal and FMT 701 cultivars. The use of two 3rd instar of S. cosmioides larvae per leaf disc from the middle leaves of first open flower stage and one 3rd instar larva of C. virescens per leaf disc from the upper leaves of plants at first visible floral bub stage allowed better discrimination between genotypes as to their resistance levels. Based on these results, we evaluated the influence of commercial cotton cultivars on the feeding and developmental behavior of both pest species. For S. cosmioides were evaluated the genotypes BRS 286, BRS 293, BRS 335, BRS 336, BRS 368 RF, BRS 372, DeltaOpal, FMT 701, FMT 707, FMT 709, FM 910 and FM 993. BRS 293, BRS 335 and FMT 707 cultiv... (Complete abstract click electronic access below) / Doutor