Evaluation of different formulations of IGRs against Aedes albopictus and Culex quinquefasciatus (Diptera: Culicidae)

Objective: To test the relative efficacy of pyriproxyfen and methoprene on mortality, deformity, inhibition and emergence to adult stages of Culex quinquefasciatus and Aedes albopictus. Methods: Serial dilutions (0.01-0.05 mg/L) of methoprene, pyriproxyfen 0.5 water dispersible granules (WDG) and pyriproxyfen 1.0 WDG were used to assess mortality and inhibition of 3rd instar larvae of Aedes albopictus and Culex quinquefasciatus. Each concentration and control was replicated four times in completely randomized design. Data on larval mortality, growth inhibition, deformities and adult's emergence was recorded weekly. On the basis of best comparative performance, the efficacy of pyriproxyfen 1.0 WDG at 0.1 g/m

Evaluation of different formulations of IGRs against Aedes albopictus and Culex quinquefasciatus (Diptera:Culicidae)

Objective: To test the relative efficacy of pyriproxyfen and methoprene on mortality, deformity, inhibition and emergence to adult stages of Culex quinquefasciatus and Aedes albopictus. Methods: Serial dilutions (0.01–0.05 mg/L) of methoprene, pyriproxyfen 0.5 water dispersible granules (WDG) and pyriproxyfen 1.0 WDG were used to assess mortality and inhibition of 3rd instar larvae of Aedes albopictus and Culex quinquefasciatus. Each concentration and control was replicated four times in completely randomized design. Data on larval mortality, growth inhibition, deformities and adult's emergence was recorded weekly. On the basis of best comparative performance, the efficacy of pyr-iproxyfen 1.0 WDG at 0.1 g/m3 was also tested in the field by collecting treated water samples monthly for 1–6 months after field application. Twenty five 3rd instar larvae of Aedes and Culex spp. of the same cohorts were used for bioassays and compared with larvae in control cups containing 1 L of untreated tap water. Results: Results revealed variations in fatality of different insect growth regulators (IGRs) to the 3rd instar larvae of Culex and Aedes mosquitoes. Among the IGRs, pyr-iproxyfen 1.0 WDG was found best that exhibited significantly high emergence inhibition against Culex and Aedes spp. Based on the results, the IGRs were classified in terms of the tested parameters in order of pyriproxyfen 1.0 WDG > pyriproxyfen 0.5 WDG > methoprene. In case of field studies, pyriproxyfen 1.0 WDG, pool data of the entire target treated sites showed minimum adult emergence from water sampled of habitats treated with 0.1 g/m3 of pyriproxyfen 1.0 WDG. Conclusions: It is thus concluded that IGRs can be utilized as environment friendly control measures for Culex and Aedes spp. of mosquitoes on small and large scale. This will reduce the use of conventional insecticides by the public health authorities and help in reducing selection pressure of insecticides.

Efecto del regulador de crecimiento pyriproxyfen sobre Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae) de La Pedrera, Maracay, estado Aragua, Venezuela / Effect of the growth regulator pyriproxyfen on Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae) from La Pedrera, Maracay, Aragua, Venezuela

Pyriproxyfen es un análogo sintético de la hormona juvenil ampliamente usado para el control de mosquitos. Esta investigación describe bioensayos realizados en condiciones de laboratorio con una formulación granulada del producto (Sumilarv G-0,5 %), utilizando larvas del IV instar temprano de Aedes aegypti. Se realizaron estos bioensayos con el fin de determinar su eficacia y actividad residual a las dosis de 0,01; 0,02; 0,03; 0,04 y 0,05 ppm sobre larvas Aedes aegypti de las cepas La Pedrera y Rockefeller de referencia; las evaluaciones fueron realizadas a 1, 7, 15, 30, 45, 60, 75 y 90 días después del tratamiento. Los resultados evidenciaron que especímenes tratados, presentaron malformaciones que afectaron su desarrollo y causaron la muerte de los individuos. Fue calculado el porcentaje de mortalidad de larvas, pupas y adultos, asimismo el porcentaje de inhibición de emergencia de adultos. La media aritmética para el porcentaje de mortalidad (% M) en la cepa Rockefeller fue de 76,83 % y para la cepa La Pedrera de 65,37 %. Para el porcentaje de inhibición de la emergencia, la cepa Rockefeller presentó media aritmética de 91,80 %; la cual fue significativamente mayor que la de la cepa La Pedrera, que fue igual a 78,08 %. El producto pyriproxyfen mostró eficacia en la inhibición de la emergencia de adultos con las dosis evaluadas, pero para la dosis de 0,01 ppm fue de menor efecto residual. Los resultados demuestran una mayor eficacia y actividad residual del pyriproxyfen a las dosis de 0,04 y 0,05 ppm hasta los 90 días después del tratamiento; en efecto ambas dosis presentaron elevada eficacia y actividad residual prolongada por 90 días, sugiriendo su uso como alternativa en los programas de control de Aedes aegypti y para el manejo integrado de otros mosquitos vectores en Venezuela, como es el caso de Aedes albopictus.

Pyriproxyfen is a synthetic juvenile hormone analogue widely used in mosquito control. Bioassays were undertaken to evaluate the efficacy and residual activity of a granular formulation of pyriproxyfen (Sumilarv G- 0.5% in granules) against IV instar Aedes aegypti (La Pedrera and Rockefeller reference strains), at doses of 0.01; 0.02; 0.03; 0.04 and 0.05 ppm. Larvae were examined 1, 7, 15, 30, 45, 60, 75 and 90 days after treatment. The treated specimens showed malformations affecting their development, and higher mortality rates compared to the controls. The percentage mortality of larvae, pupae and adults and the percentage of adult emergence inhibition were calculated. Mortality rates (% M) were 76.83 % (Rockefeller strain) and 65.37 % (La Pedrera strain). The percentage of adult emergence inhibition was significantly higher (91.80 %) in the Rockefeller strain than the La Pedrera strain (78.08 %). Pyriproxyfen produced effective inhibition of adult emergence at all the doses evaluated, but with less residual effect at 0.01 ppm. Doses of 0.04 and 0.05 ppm were the most efficient and persistent over the 90 days of the experiment. The results suggest that pyriproxyfen could be used as an alternative in Aedes aegypti control strategies and integrated mosquito vector management programs in Venezuela.

Eficacia y actividad residual del regulador de crecimiento pyriproxyfen sobre larvas de Aedes aegypti (Diptera: Culicidae) en condiciones de laboratorio / Efficacy and residual activity of insect growth regulator pyriproxyfen on larvae of Aedes aegypti (Diptera: Culicidae) under laboratory conditions

Pyriproxyfen es un análogo sintético de la hormona juvenil ampliamente usado para el control de mos quitos. Esta investigación describe bioensayos realizados en condiciones de laboratorio con una formulación granulada del producto, utilizando larvas del IV instar de aedes aegypti. Este producto (Sumilarv G-0,5%) fue formulado en Brasil, con 0,5 % del ingrediente activo (Pyriproxyfen: S-31183). El objetivo fue determinar la eficacia del producto y evaluar su acción residual a tres concentraciones (0,002; 0,01 y 0,05 ppm) sobre larvas de Ae. aegypti. Para tal fin, se realizaron seis ensayos sucesivos: El ensayo inicial (semana 0) y después a 1, 2, 4, 6 y 8 semanas post-tratamiento al agua. Según los resultados obtenidos, la actividad residual del producto con la concentración de 0,05 ppm, fue bastante satisfactoria durante 8 semanas (60 días) post-tratamiento, obteniéndose valores del porcentaje de Inhibición de la Emergencia (% IE) de 77%. Sin embargo, tanto a 0,002 ppm como a 0,01 ppm, su eficacia disminuyó considerablemente a partir de la primera y segunda semana post-tratamiento. La mortalidad en la fase de pupa fue mucho mayor que la mortalidad larval a todas las concentraciones probadas. Asimismo, en otro experimento se evaluó el efecto del aumento de la densidad de larvas expuestas, sobre la eficacia del producto a la misma concentración de 0,05 ppm. La densidad larvaria no afectó la eficacia del producto; ya que no hubo diferencias estadísticamente significativas entre tratamientos o densidades probadas. El análisis estadístico no reveló ninguna relación significativa entre densidad larvaria y mortalidad de pupas o inhibición de la emergencia de adultos de Ae. aegypti. Según lo cual, se concluye que al aumentar progresivamente la cantidad de larvas a tratar, no disminuye la mortalidad de pupas, ni la inhibición de emergencia de adultos, por lo que no se afecta negativamente la eficacia del producto.

Pyriproxyfen is a synthetic juvenile hormone analogue and it has been widely used in mosquito control. This re search paper describes experiments or trials carried out under laboratory conditions with a granular formulation of pyriproxyfen (Sumilarv -G 0.5% in granules), using IV instars larvae of Aedes aegypti. This is a granular formulation of pyriproxyfen with 0.5% of active ingredient. The efficacy and residual activity of pyriproxyfen were evaluated on larvae and pupae of Ae. aegypti using three final concentrations: 0.002, 0.01 and 0.05 ppm; at (initial day = week 0) and at 1, 2, 4, 6 and 8 weeks after treatment (post-treatment). According to the results, the efficacy of pyriproxyfen was very satisfactory during 8 weeks (60 days) post-treatment, using 0.05 ppm of pyriproxyfen with 77% (% IE). It was observed that mortality in the pupa stage was higher than larvae mortality for all three concentrations. However, the percentage of IE in treated water diminished after the initial week (week 0) to 56.7 % (0.002 ppm) and after first week to 98.8 % (0.01ppm). The other aim of the study was to evaluate the efficacy of pyriproxyfen at 0.05 ppm, in relation to the larval density of Aedes aegypti under laboratory conditions. Five larval densities: 25, 50, 75, 100 and 125 larvae, were evaluated at 0.05 ppm. The statistical analysis not revealed significant differences between these densities, and did not reveal a relationship between the mosquito larval density and pupae mortality of Ae. aegypti. Whereby, it is concluded that by progressively increasing the number of larvae treated, mortality of pupae or adult emergence inhibition do not decrease, therefore it does not adversely affect the product performance.

Susceptibility of Aedes aegypti (L) to the insect growth regulators diflubenzuron and methoprene in Uberlândia, State of Minas Gerais

Aedes aegypti (L) (Diptera: Culicidae) was reared in several concentrations of diflubenzuron and methoprene under laboratory conditions in Uberlândia, State of Minas Gerais, southeastern Brazil. Characteristics such as LC50 and LC95, the susceptibility of immature stages of different ages to these insect growth regulators and their residual effects were studied. The LC50 and LC95 of diflubenzuron and methoprene were 5.19 and 12.24 ppb; 19.95 and 72.08 ppb, respectively. While diflubenzuron caused great mortality in all larval instars, methoprene was more effective when the mosquito was exposed from the start of the fourth larval instar onwards. Commercial concentrations of these two insect growth regulators close to LC95 presented greater residual activity than did their respective technical formulations. The parameters were compared with those obtained elsewhere. The characteristics investigated here indicate that these insect growth regulators are effective alternatives for controlling the dengue vector in the Uberlândia region.

Aedes aegypti (L) (Diptera: Culicidae) foi criado em várias concentrações de diflubenzuron e methoprene sob condições de laboratório em Uberlândia, Minas Gerais, sudeste do Brasil. Foram estudados aspectos tais como, CL50 e CL95, suscetibilidade de estágios imaturos de diferentes idades a estes insect growth regulators e seu efeito residual. As CL50 e CL95 de diflubenzuron e methoprene foram: 5,19 e 12,24ppb; 19,95 e 72,08ppb, respectivamente. Enquanto diflubenzuron causou grande mortalidade em todos os estádios larvais, methoprene causou maior mortalidade quando o mosquito foi exposto a partir do início do quarto estádio larval. As concentrações comerciais dos dois insect growth regulators próximas às CL95 mostraram maior atividade residual que suas respectivas formulações técnicas. Os parâmetros são comparados com aqueles obtidos em outros locais. Os aspectos aqui investigados indicam estes insect growth regulators como alternativas efetivas para o controle do vetor da dengue na região de Uberlândia.

Efeitos de três análogos do hormônio juvenil aplicados em bicho-da-seda, Bombyx mori L. (Lepidoptera: Bombycidae) / Effects of three juvenile hormone analogues applied on the silkworm, Bombyx mori L. (Lepidoptera: Bombycidae)

Juvenile hormone analogues (JHA) have been tested as growth regulators of Bombyx mori L., aiming to increase the cocoon production. These chemicals, when applied in appropriate doses, promote prolongation of the larval period. The effects of JHA application may vary with the product, strain, and time of application. The objective of this study was to evaluate the topical application in different times of three JHA and their effects on larval growth and silk production of the Brazilian silkworm strain C115xN108. Pyriproxyfen, methoprene and fenoxycarb were applied on silkworm larvae at 24h, 48h, 72h or 96h after the beginning of the fifth instar (HFI) and the effects of the products on larval and adult biological characters and silk production were evaluated. Independently of the time of application, the three products affected all the evaluated parameters. The nutrients stored during the extended period by the treated insects were used for growing the silk glands and were converted in corporal weight, with consequent increments in the silk production. Applications of piryproxyfen, methoprene and fenoxycarb between 48 and 72 HFI promoted, in a general way, the largest increments in the biomass and cocoon production of B. mori. Variations in the time of application between 24 and 96 HFI did not influence adult emergence, oviposition or the egg viability of B. mori.

Análogos do hormônio juvenil (AHJ) têm sido testados como reguladores de crescimento de Bombyx mori L., com vistas ao incremento da produção de casulos. Esses produtos, quando aplicados em doses adequadas, prolongam o período larval. Os efeitos da aplicação de AHJ podem variar com o produto, a linhagem e o momento de aplicação. Este estudo teve por objetivo avaliar o efeito da aplicação tópica, em diferentes momentos, de três análogos do hormônio juvenil sobre o crescimento dos insetos e a produção de seda da linhagem brasileira C115xN108 do bicho-da-seda. Os produtos piriproxifem, metoprene e fenoxicarbe foram aplicados em larvas do bicho-da-seda a 24h, 48h, 72h e 96h após o início do quinto ínstar (HQI) e seus efeitos sobre características biológicas larvais e adultas e a produção de seda foram avaliados. Independentemente do momento de aplicação, os três produtos afetaram todos os parâmetros avaliados. A reserva de nutrientes acumulada durante o período larval prolongado dos insetos tratados foi destinada ao crescimento das glândulas sericígenas e, também, convertida em peso corporal, com conseqüentes incrementos na produção de seda. Aplicações entre 48 e 72 HQI provocaram os maiores incrementos na biomassa e na produção de casulos de B. mori. Variações no momento de aplicação de 24h e 96h não influenciaram a emergência ou a oviposição de adultos de B. mori, nem a viabilidade dos ovos.