Due to concerns with synthetic neurotoxic insecticides used in insect pest management, alternative control methods are sought. Methoprene is a juvenile hormone analogue, which is well-known for its lethal effects on immature insects, and is registered as a stored-grain insecticide in the U.S.A. and Australia. However, less is known about its sub-lethal effects. Experiments were conducted to investigate the effects of methoprene (Diacon II) on heat tolerance, cold tolerance and progeny production of Tribolium castaneum (Herbst) when late-instar larvae or adults were exposed to wheat treated with methoprene. Methoprene at 3.33 ppm or higher, reduced heat tolerance of adults at 46ºC. In contrast, methoprene did not affect the heat tolerance of larvae. Cold tolerance and cold acclimation of both adults and larvae was not affected by methoprene. Exposure of larvae to 0.001 or 0.0165 ppm of methoprene on wheat had 37 and 72% reduction in adult emergence, respectively. The surviving adults had normal movement, but their progeny production was reduced by 71%. Males were affected more than females. Exposure of adults to methoprene (66.6 ppm) did not reduce progeny production. Methoprene is used as a surface treatment to control insects in empty grain bins, processing facilities and warehouses. Experiments were conducted to assess the effect of surface material, temperature and cleaning practices on methoprene residual efficacy. A bioassay with late-instar larvae at 30ºC until adult emergence was used to measure methoprene residual efficacy. Methoprene applied at the label rate (0.0003 mg/cm2) on varnished wood, held at 20, 30 or 35ºC for 24 weeks, prevented all development of larvae into adults. Conversely, concrete surfaces allowed 22% adult emergence after 8 weeks and 69% after 24 weeks. Temperatures, 20, 30 or 35ºC, that the concrete surfaces were held before the bioassay, did not affect this decline in efficacy. Presence of flour or repeated removal of flour (cleaning) reduced the efficacy of methoprene on concrete surfaces, but not on varnished wood. Maintaining concrete surfaces at 65ºC for 48 hours did not reduce efficacy. The implications of these results are discussed in the context of controlling stored-product insects, as well as insect physiology.

Methoprene is a Juvenile Hormone (JH) analogue commonly used for the control of mosquito larvae. When applied to a mosquito breeding site, methoprene enters the haemolymph, where it mimics the function of JH and interferes with normal metamorphosis, resulting in larval mortality. Methoprene is commonly used for the control of larvae and has not been used as an adulticide, due to an absence of acute effects. This study evaluated possible chronic effects caused by the exposure of adult Aedes mosquitoes to methoprene. Methoprene was applied, in both technical grade and the commercially available Altosid®, topically to adults through droplet application on the abdomen and as a spray application. Mosquitoes were examined for treatment effects on ovary development, adult male and female mortality, and fecundity. The results demonstrate that relatively high doses are required to affect adult survivorship. In contrast, significant impacts on both fecundity and egg hatch were observed for females treated at the lower dosages. I discuss the results in relation to autocidal strategies for mosquito control in which the release of fecund females is to be avoided.

Due to concerns with synthetic neurotoxic insecticides used in insect pest management, alternative control methods are sought. Methoprene is a juvenile hormone analogue, which is well-known for its lethal effects on immature insects, and is registered as a stored-grain insecticide in the U.S.A. and Australia. However, less is known about its sub-lethal effects. Experiments were conducted to investigate the effects of methoprene (Diacon II) on heat tolerance, cold tolerance and progeny production of Tribolium castaneum (Herbst) when late-instar larvae or adults were exposed to wheat treated with methoprene. Methoprene at 3.33 ppm or higher, reduced heat tolerance of adults at 46ºC. In contrast, methoprene did not affect the heat tolerance of larvae. Cold tolerance and cold acclimation of both adults and larvae was not affected by methoprene. Exposure of larvae to 0.001 or 0.0165 ppm of methoprene on wheat had 37 and 72% reduction in adult emergence, respectively. The surviving adults had normal movement, but their progeny production was reduced by 71%. Males were affected more than females. Exposure of adults to methoprene (66.6 ppm) did not reduce progeny production. Methoprene is used as a surface treatment to control insects in empty grain bins, processing facilities and warehouses. Experiments were conducted to assess the effect of surface material, temperature and cleaning practices on methoprene residual efficacy. A bioassay with late-instar larvae at 30ºC until adult emergence was used to measure methoprene residual efficacy. Methoprene applied at the label rate (0.0003 mg/cm2) on varnished wood, held at 20, 30 or 35ºC for 24 weeks, prevented all development of larvae into adults. Conversely, concrete surfaces allowed 22% adult emergence after 8 weeks and 69% after 24 weeks. Temperatures, 20, 30 or 35ºC, that the concrete surfaces were held before the bioassay, did not affect this decline in efficacy. Presence of flour or repeated removal of flour (cleaning) reduced the efficacy of methoprene on concrete surfaces, but not on varnished wood. Maintaining concrete surfaces at 65ºC for 48 hours did not reduce efficacy. The implications of these results are discussed in the context of controlling stored-product insects, as well as insect physiology.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Aedes aegypti (L.), the vector of urban yellow fever and dengue, is controlled in Brazil mainly by the use of the organophosphate Temephos. Resistance to Temephos has been described in Brazil and in other countries as well. Insect Growth Regulators (IGRs), Diflubenzuron (chitin synthesis inhibitor) and Methoprene (juvenile hormone analog), are insecticides that affect the development of insects by affecting adult emergence. A. aegypti susceptibility to Diflubenzuron and Methoprene was investigated in Uberlândia, by studying the 50% and 95% lethal concentrations of both IGRs for the A. aegypti population (LC50 and LC95) and their action on the immature stages. In addition, other aspects, such as IGRs residual activity and the effect of sublethal dosages upon adult symmetry, size, weight, fecundity, fertility and longevity were investigated. The experiments were done in laboratory conditions using individuals from a colony originated from eggs collected in the urban area of Uberlândia. The number of replicates was six in all assays. The confidence level adopted in all the statistical analysis was 95%. The LC50 and LC95 of Diflubenzuron and Methoprene were 5.19 and 12.24 ppb; 19.95 and 72.08 ppb, respectively. Diflubenzuron was effective in all larvae instars and Methoprene caused greater mortality when the mosquito was exposed from the early fourth instar larvae on. Concentrations of commercial IGRs presented greater residual activity than did the technical formulations. Increased levels of fluctuating asymmetry were observed in the mosquitoes exposed to Diflubenzuron. Females treated with Methoprene showed smaller weight than did the untreated females. On the other hand, the longevity of the mosquito was reduced in the groups treated with both IGRs. The LC50 and LC95 of Diflubenzuron obtained here are compatible with the values observed for this IGR in other studies, while the LCs of Methoprene were higher than those generally reported in the literature. However, the results obtained here indicate that Diflubenzuron and Methoprene are potential tools to control this mosquito in the region of Uberlândia. / Aedes aegypti (L.), vetor da febre amarela urbana e da dengue, é controlado no Brasil utilizando-se principalmente o organofosforado Temephos. Tem-se registrado a ocorrência de resistência deste mosquito ao Temephos aqui e em outros países. Os Reguladores de Crescimento de Insetos (IGRs) Diflubenzuron (inibidor de síntese de quitina ) e Methoprene (análogo ao hormônio juvenil) são um grupo de inseticidas que afetam o desenvolvimento do inseto. A susceptibilidade de A. aegypti a estes IGRs foi investigada em Uberlândia a partir da obtenção das concentrações letais para 50% e 95% da população de mosquitos (CL50 e CL95) e sua atuação nas formas imaturas deste mosquito. Também foram investigados outros aspectos da susceptibilidade tais como, atividade residual destes IGRs e efeitos de dosagens subletais sobre a simetria, tamanho, peso, fecundidade, fertilidade e longevidade de adultos. Os experimentos foram realizados em laboratório com indivíduos de uma colônia originária de ovos colhidos na região urbana de Uberlândia. O número de réplicas dos grupos tratados e controles se manteve em seis em todos os experimentos. Foi adotado o nível de confiança de 95% em todas as análises estatísticas. As CL50 e CL95 obtidas para Diflubenzuron e Methoprene foram: 5,19 e 12,24 ppb; 19,95 e 72,08 ppb, respectivamente. Diflubenzuron mostrou-se efetivo em todos os estádios larvais, enquanto Methoprene causou maior mortalidade quando o mosquito foi exposto a partir do início do quarto estádio larval. As formulações comerciais dos IGRs apresentaram maior atividade residual que suas respectivas formulações técnicas. Níveis aumentados de assimetria flutuante foram observados nos mosquitos expostos ao Diflubenzuron. Fêmeas tratadas com Methoprene apresentaram menor peso que as não tratadas. Por outro lado, a longevidade do mosquito foi reduzida nos grupos tratados com ambos os produtos. Os valores das CL50 e CL95 registrados para Diflubenzuron estão dentro do intervalo de variação observados na literatura para este IGR. Já os valores registrados para Methoprene estão acima dos observados em outros locais, indicando uma relativa tolerância natural da população de A. aegypti de Uberlândia a este IGR. No entanto, os resultados aqui obtidos indicam Diflubenzuron e Methoprene como alternativas para o controle do vetor da dengue na região de Uberlândia. / Doutor em Imunologia e Parasitologia Aplicadas

This thesis comprises three published papers and one manuscript, all focused on the role of juvenile hormone (JH), the JH receptor Methoprene-tolerant (Met) and its target gene Krüppel-homolog 1 (Kr-h1) in insect development and reproduction. The JH-Met-Kr-h1 pathway is critical for metamorphic transition in hemimetabolan Pyrrhocoris apterus (Hemiptera) and holometabolan Bombyx mori (Lepidoptera) but seems to be dispensable during early larval postembryonic development. The results also show that Met and its heterodimeric partner Taiman (Tai) but not Kr-h1 are critical for ovarian development and vitellogenesis in Pyrrhocoris females. In vitro, in vivo and cell-based techniques in Drosophila melanogaster have demonstrated that Met and its paralog Gce are a bona fide receptor for JH. Only Gce capable of binding JH rescued Drosophila deficient for Met and Gce proteins, and the capacity of Gce to bind JH was necessary for JH-dependent transcriptional activation by Gce and Tai.