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Homopteran insect pests can cause severe economical damage to crop plants by both direct physical means and as vectors of plant viral diseases. They are notoriously difficult insects to control by conventional methods, primarily due to their ability to evolve resistance-breaking biotypes within a relatively short time period. The production of genetically modified crop plants, expressing insecticidal genes, offers a novel method of control for a wide range of insect species. Once suitable gene products, such as plant- derived proteins, have been identified as having insecticidal effect against specific insects in vitro, their effect can be determined in vivo by expressing the relevant gene in transgenic plants. Insect feeding trials were carried out to determine the effects of incorporating a range of plant-derived proteins into artificial diets fed to planthopper, leafliopper and aphid pests and to aphids in planta. The lectins Galanthus nivalis agglutinin (GNA) and wheat germ agglutinin (WGA), and the enzyme soybean lipoxygenase (LPO) were shown to exhibit significant antimetabolic effects towards first and third instar nymphs of rice brown planthopper (Nilaparvata lugens Stal) when incorporated into artificial diet at 0 1% {w/v}, 0-1% (w/v) and 0 08% {w/v} levels respectively. The lectin GNA was also shown to exhibit a significant antimetabolic effect towards third instar nymphs of the rice green leafhopper (Nephottetix cinciteps Uhler) and the peach potato aphid {Myzus persicae Sulzer). A number of inert proteins, lectins, protein inhibitors and enzymes also tested showed relatively little or no effect towards both insects. The mechanism of action of all three effective proteins was examined using BPH as a model insect. As judged by honeydew production, the proteins all had a deterrent effect on insect feeding. However, subsequent toxic effects are also indicated. When fed sub-optimal concentrations of effective proteins in combination no synergistic or additive effects were observed, indicating that pyramiding the genes of these effective proteins would be of no advantage in protecting the crop against BPH.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 85-89).

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Orientador: Janete Apparecida Desidério / Coorientador: Odair Aparecido Fernandes / Banca: Maria Inês Tiraboschi Ferro / Banca: Juliana Regina Vieira da Costa / Resumo: A bactéria Bacillus thuringiensis (Bt) possui a capacidade de produzir inclusões protéicas (proteína Cry) e proteínas vegetativas (Vip). Estas proteínas podem ser tóxicas para insetos e por meio de transgenia, a expressão em plantas, podem também proporcionar controle de importantes pragas agrícolas. Nesse sentido, esta pesquisa teve por objetivo avaliar o potencial de controle das proteínas Cry1Aa, Cry1Ac, Cry1Ca, Vip3A(1), Vip3A(2) e Vip3A(3) em uma população brasileira da lagarta-da-maçã, Heliothis virescens (Lepidoptera: Noctuidae), bem como o efeito subletal e efeito sinérgico entre estas proteínas e a proteólise pelo suco do intestino do inseto praga em estudo. Para tanto, clones de Escherichia coli recombinantes portadores de genes únicos foram cultivados em meio para a indução das proteínas e os lisados obtidos foram utilizados para as análises de toxicidade por meio de bioensaios. Diferentes concentrações protéicas foram utilizadas para conduzir os bioensaios. A mortalidade foi avaliada e obteve-se a CL50. Desta forma, observou-se que, dentre as proteínas testadas, Cry1Ac (CL50 39,89 ng.cm-2), Vip3A(2) (CL50 945,77 ng.cm-2) e Vip3A(3) (CL50 874,45 ng.cm-2 ) foram as mais tóxicas e houve correlação negativa entre a concentração de proteínas e o peso das lagartas. Nos ensaios referentes ao efeito sinérgico das proteínas, ativadas e não ativadas com tripsina comercial, foram encontradas possíveis combinações eficientes no controle da praga em estudo destacando-se Vip3A(2)/Cry1Aa, Vip3A(1)/Cry1Aa, Vip3A(1)/Cry1Ac, e Vip3A(2)/Cry1Ac. Os resultados referentes à interação das enzimas digestivas do intestino de H. virescens com as toxinas Cry1 e Vip3A permitiram constatar que as proteínas são ativadas / Abstract: Bacillus thuringiensis (Bt) produces protein inclusions (Cry proteins) and vegetative proteins (Vip). Such proteins may act as toxic to some insects and through transgenesis plants they may be able to control important agricultural pests. Thus this work aimed to evaluate the control potential of Cry1Aa, Cry1Ac, Cry1Ca, Vip3A(1), Vip3A(2) and Vip3A(3) proteins in a Brazilian population of Heliothis virescens (tobacco budworm) (Lepidoptera: Noctuidae), as well as to analyze the sublethal and the synergic effects among these proteins and the proteolysis on the intestinal juice of this pest. In order to do this, Escherichia coli clones expressing each one of the above mentioned proteins were induced to produce them and the obtained lysates were used to determine the level of toxicity through bioassays with neonatal larvae of H. virescens. Different protein concentrations were used to carry out the bioassays. The mortality was evaluated and it was possible to detect the CL50. It was possible to observe that among the tested proteins, Cry1Ac (CL50 39.89 ng.cm-2), Vip3A(2) (CL50 945,77 ng.cm-2) and Vip3A (3) (CL50 874,45 ng.cm-2) were the most toxic and showed a negative correlation between the protein concentration and larvae weight. During the bioassays concerning the synergistic effect of these proteins, which were either previously activated or not using commercial trypsin, there we found efficient combinations for the control of the pest under study in this work, being that the combinations Vip3A(2)/Cry1Aa, Vip3A(1)/Cry1Aa, Vip3A(1)/Cry1Ac and Vip3A(2)/Cry1Ac were considered the best ones. The results with reference to the interaction of the digestive enzymes from the intestine of H. virescens larvae when using the toxins Cry1 and Vip3A allowed us to detect that these proteins are activated / Mestre

Made available in DSpace on 2014-06-11T19:26:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-17Bitstream added on 2014-06-13T20:14:43Z : No. of bitstreams: 1 lemes_arn_me_jabo.pdf: 416795 bytes, checksum: 44abf4d7c9c15c73531d86dc762390a5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A bactéria Bacillus thuringiensis (Bt) possui a capacidade de produzir inclusões protéicas (proteína Cry) e proteínas vegetativas (Vip). Estas proteínas podem ser tóxicas para insetos e por meio de transgenia, a expressão em plantas, podem também proporcionar controle de importantes pragas agrícolas. Nesse sentido, esta pesquisa teve por objetivo avaliar o potencial de controle das proteínas Cry1Aa, Cry1Ac, Cry1Ca, Vip3A(1), Vip3A(2) e Vip3A(3) em uma população brasileira da lagarta-da-maçã, Heliothis virescens (Lepidoptera: Noctuidae), bem como o efeito subletal e efeito sinérgico entre estas proteínas e a proteólise pelo suco do intestino do inseto praga em estudo. Para tanto, clones de Escherichia coli recombinantes portadores de genes únicos foram cultivados em meio para a indução das proteínas e os lisados obtidos foram utilizados para as análises de toxicidade por meio de bioensaios. Diferentes concentrações protéicas foram utilizadas para conduzir os bioensaios. A mortalidade foi avaliada e obteve-se a CL50. Desta forma, observou-se que, dentre as proteínas testadas, Cry1Ac (CL50 39,89 ng.cm-2), Vip3A(2) (CL50 945,77 ng.cm-2) e Vip3A(3) (CL50 874,45 ng.cm-2 ) foram as mais tóxicas e houve correlação negativa entre a concentração de proteínas e o peso das lagartas. Nos ensaios referentes ao efeito sinérgico das proteínas, ativadas e não ativadas com tripsina comercial, foram encontradas possíveis combinações eficientes no controle da praga em estudo destacando-se Vip3A(2)/Cry1Aa, Vip3A(1)/Cry1Aa, Vip3A(1)/Cry1Ac, e Vip3A(2)/Cry1Ac. Os resultados referentes à interação das enzimas digestivas do intestino de H. virescens com as toxinas Cry1 e Vip3A permitiram constatar que as proteínas são ativadas / Bacillus thuringiensis (Bt) produces protein inclusions (Cry proteins) and vegetative proteins (Vip). Such proteins may act as toxic to some insects and through transgenesis plants they may be able to control important agricultural pests. Thus this work aimed to evaluate the control potential of Cry1Aa, Cry1Ac, Cry1Ca, Vip3A(1), Vip3A(2) and Vip3A(3) proteins in a Brazilian population of Heliothis virescens (tobacco budworm) (Lepidoptera: Noctuidae), as well as to analyze the sublethal and the synergic effects among these proteins and the proteolysis on the intestinal juice of this pest. In order to do this, Escherichia coli clones expressing each one of the above mentioned proteins were induced to produce them and the obtained lysates were used to determine the level of toxicity through bioassays with neonatal larvae of H. virescens. Different protein concentrations were used to carry out the bioassays. The mortality was evaluated and it was possible to detect the CL50. It was possible to observe that among the tested proteins, Cry1Ac (CL50 39.89 ng.cm-2), Vip3A(2) (CL50 945,77 ng.cm-2) and Vip3A (3) (CL50 874,45 ng.cm-2) were the most toxic and showed a negative correlation between the protein concentration and larvae weight. During the bioassays concerning the synergistic effect of these proteins, which were either previously activated or not using commercial trypsin, there we found efficient combinations for the control of the pest under study in this work, being that the combinations Vip3A(2)/Cry1Aa, Vip3A(1)/Cry1Aa, Vip3A(1)/Cry1Ac and Vip3A(2)/Cry1Ac were considered the best ones. The results with reference to the interaction of the digestive enzymes from the intestine of H. virescens larvae when using the toxins Cry1 and Vip3A allowed us to detect that these proteins are activated

The insecticide dichloro-diphenyl-trichloroethane (DDT) is widely used in indoor residual spraying (IRS) for malaria control owing to its longer residual efficacy compared to other World Health Organization (WHO) alternatives. It was envisaged that by investigating mechanisms of degradation of these alternative insecticides, a better understanding would be obtained on strategies of stabilising them and rendering their efficacy comparable with or better than DDT, hence providing less controversial and more acceptable and effective alternative insecticide formulations to DDT. This study sought to investigate the reasons behind the reported longer lasting behaviour of DDT by exposing all the WHO approved insecticides to high temperature, high humidity and ultra-violet light. Interactions between the insecticides and some mineral powders in the presence of an aqueous medium were also tested. Simple insecticidal paints were made using slurries of these mineral powders whilst some insecticides were dispersed into a conventional acrylic paint binder. These formulations were then spray painted on neat and manure coated mud plaques, representative of the material typically used in rural mud houses, at twice the upper limit of the WHO recommended dosage range. DDT was applied directly onto mud plaques at four times the WHO recommended concentration and on manure plaques at twice WHO recommended concentration. All plaques were subjected to accelerated ageing conditions of 40 °C and a relative humidity of 90%. In the accelerated ageing tests, Fourier transform infra-red (FTIR) interferograms showed that pyrethroids were the most stable insecticides compared to carbamates and DDT. High temperature oxidation, ultra violet light and humidity were ruled out as the cause of failure of the alternative insecticides. Gas chromatography (GC) interferograms showed that phosphogypsum stabilised the insecticides the most against alkaline degradation. Bioassay testing showed that the period of efficacy of these formulations was comparable to that of DDT sprayed at 4 times the upper limit of the WHO recommended dosage range. Bioassay testing also showed that these insecticidal “paint” formulations stabilised the insecticides on cattle manure coated surfaces as compared to DDT sprayed directly on similar surfaces. Bioassay experiments indicated that incorporating insecticides into a conventional paint binder or adsorbing them onto phosphogypsum provided effective life spans, under accelerated ageing conditions, comparable to or exceeding that of DDT directly applied to typical soil substrates. Best results were obtained with propoxur in standard acrylic emulsion paint. Similarly, insecticides adsorbed on phosphogypsum and sprayed on cattle manure coated surfaces provided superior lifespans compared with DDT sprayed directly on a similar surface. Copyright / Dissertation (MEng)--University of Pretoria, 2012. / Chemical Engineering / unrestricted

Les paysans stockent entre 60 et 80% de la production des grains qui est régulièrement infestée par les insectes ravageurs. Les plantes insecticides méritent dêtre valorisées à travers notamment leur huile essentielle afin de limiter la dépendance des paysans aux insecticides chimiques, largement utilisés au Nord du Cameroun et dont les dangers sont bien connus. Lanalyse chromatographique de quelques huiles essentielles locales, révèle que Cymbopogon citratus (DC.) Stapf. (Poacée), Ocimum gratissimum L. (Lamiacée) et Ocimum suave Willd (Lamiacée) sont constituées respectivement du citral, du thymol et de leugénol à plus de 50%. Les huiles essentielles de Annona senegalensis Pers. (Annonacée), Hyptis spicigera Lam. (Lamiacée), et Xylopia aethiopica (Dunal) A. Rich. (Annonacée), contiennent majoritairement des monoterpènes hydrocarbonés dont lα-phellandrène, lα-pinène, le sabinène et le β-pinène. H. spicigera et X. aethiopica, dont la composition varie suivant lorigine de la plante, sont les plus efficaces contre Callosobruchus maculatus (F.) et Sitophilus zeamais (Motsch.), principaux ravageurs primaires des greniers au Nord du Cameroun. Lactivité insecticide de H. spicigera est marquée par sa teneur en α-pinène (39,0%) tandis que celle de X. aethiopica est due à leffet synergique de ses composés. La volatilité des huiles essentielles nécessite des supports aptes à réguler le relarguage des molécules volatiles. Avec plus de 90% de molécules volatiles libérées en 7 jours, la poudre des infrutescences de X. aethiopica, qui contiennent plus de 5% dhuile essentielle, bien que toxique contre C. maculatus, ne permet pas de réguler et de prolonger la libération des molécules volatiles. Le kaolin testé dégrade lhuile essentielle X. aethiopica tandis que lincorporation de lamidon à la gomme arabique permet de libérer en 7 jours, 40,5 à 55,9% des molécules volatiles suivant la proportion damidon. Cette combinaison est un système qui autorégule le relarguage en deux phases. La première phase a un taux de relarguage élevé qui entraîne un effet « Knock down » sur C. maculatus, et la seconde phase présente un relarguage lent et prolongé qui pourrait, par un effet répulsif, éviter linfestation des grains stockés. Cette étude est une contribution du projet « STOREPROTECT PIC-2003 » à la protection des denrées stockées par lutilisation des ressources locales au Nord du Cameroun.

During recent years most of the successful developments in pyrethroids have been primarily concerned with structural or compositional variations. As a part of our continuing interest in pyrethroid insecticides, nitrogen-containing compounds having pyrethroid-like structures were synthesized. Seven prolinate compounds, N-(substituted)-phenyl-prolinates and N-carbobenzoxy-prolinates were coupled with known pyrethroid alcohols. These structural variations which "locked in" a specific conformation between the nitrogen and chiral a-carbon in the acid moiety of fluvalinate were studied to determine the influence of certain conformations on insecticidal toxicity. The toxicity data for the prolinate compounds showed intermediate mortality against nonresistant cockroaches. It was concluded that the conformation imposed by the proline ring portion of the esters was probably close to the favored conformation for interaction of fluvalinate-like pyrethroids with the insect receptor site. A second series of nitrogen-containing compounds, twenty-five carbamate esters resulting from the condensation of N-isopropyl-(substituted)-anilines and N-alkyl-(substituted)-benzylamines with appropriate pyrethroid alcohols were studied for insecticidal activity. These studies were conducted on pyrethroid-susceptible houseflies. Some of the carbamate esters exhibited high toxicity when synergized by piperonyl butoxide. For example, the toxicity ( LD 50 ) of O-a-cyano-3-phenoxyfaenzyl-N-a,a-dimethyl-4-bromo-benzyl carbamate was 0.012 ug/g, which is significantly greater than that reported for the potent pyrethroid, fenvalerate. Correlations of insecticidal activity with respect to structure and conformational factors of the carbamate esters have been made. The N-isopropyl substituent decreases insecticidal activity in the N-benzyl-derived compounds, while the N-isopropyl substituent enhances activity in the N-phenyl-derived compounds. Certain substituents on the phenyl ring of both analogs greatly affect insecticidal potency of the carbamate esters. Also, some alkyl substituents (especially, a,cx-dimethyl and a-cyclopropyl groups) on the benzylic carbon of the benzylamine series enhance toxicity. The a,a-dimethyl branching of the N-benzyl carbamate approximates the steric shape given by the gemdimethyl group for conventional cyclopropane ring-containing pyrethroids. The N-benzyl compounds are significantly synergized by piperonyl butoxide, particularly those in which the carbamate nitrogen atom is mono-substituted.

The synthesis and insecticidal activity of a series of 2,2-dicyano cyclopropane carboxylic acids, (3-phenoxyphenyl)- methyl esters were investigated. Synthesis of the compounds was accomplished by reaction of a dimethyl sulfonium carbethoxy ylide with propanedinitrile alkylidene compounds. Final products were formed in one step by use of the (3-phenoxyphenyl)-methyl ester of the ylide. Insecticidal activity was determined at 500 ppm application with Permethrin as the standard against houseflies, mexican bean beetles, and southern army worms.