Comparison of novaluron, pyriproxyfen, spinosad and temephos as larvicides against Aedes aegypti in Chiapas, Mexico / Comparación de novaluron, piriproxifeno, spinosad y temefos como larvicidas contra Aedes aegypti en Chiapas, México

Abstract: Objective: To compare the efficacy of three modern larvicides with the organophosphate temephos for control of Aedes aegypti in water tanks in Chiapas. Materials and methods: Trials were performed to compare the efficacy of pyriproxyfen, novaluron, two formulations of spinosad (granules and tablets) and temephos in oviposition traps and domestic water tanks. Results: Pyriproxyfen and temephos provided 2-3 weeks of complete control of larvae in oviposition traps, whereas spinosad granules and novaluron provided 7-12 weeks of control. Treatment of water tanks resulted in a significant reduction in oviposition by Ae. aegypt in houses (p<0.001). Higher numbers of larvae were present in temephos and pyriproxyfen-treated water tanks compared to novaluron and spinosad tablet treatments during most of the study. Conclusion: Spinosad formulations and novaluron were effective larvicides in this region. The poor performance of temephos may be indicative of reduced susceptibility in Ae. aegypti populations in Chiapas.

Resumen: Objetivo: Comparar la eficacia de tres larvicidas modernos para el control de Aedes aegypti en tanques de agua doméstica en Chiapas. Material y métodos: Se comparó la eficacia de piriproxifeno, novalurón, dos formulaciones de spinosad (gránulos y tabletas) y temefos en ovitrampas y tanques domésticos de agua. Resultados: El piriproxifeno y el temefos proporcionaron de 2 a 3 semanas de control de larvas en ovitrampas, mientras que los gránulos de spinosad y novaluron proporcionaron de 7 a12 semanas. Los tanques de agua tratados produjeron una reducción significativa en la oviposición por Ae. aegypti en las casas (p<0.001). Se encontró gran cantidad de larvas en los tanques tratados con temefos y piriproxifeno en comparación con los tratados con novaluron y tabletas de spinosad durante la mayor parte del estudio. Conclusión: Las formulaciones de spinosad en tabletas y novaluron fueron larvicidas efectivos en esta región. El bajo desempeño de temefos puede indicar una susceptibilidad reducida en poblaciones de Ae. aegypti en Chiapas.

Control de Aedes (Stegomyia) aegypti utilizando Bacillus thuringiensis var. israelensis en Armenia, Quindío, Colombia / Control of Aedes (Stegomyia) aegypti using Bacillus thuringiensis var. israelensis in Armenia, Quindío, Colombia

RESUMEN En Colombia, Aedes aegypti es resistente a la mayoría de insecticidas utilizados. Debido al lento desarrollo de resistencia a Bacillus thuringiensis var. israelensis (Bti), así como su alta especificidad e inocuidad ambiental, el uso de este larvicida, se torna una alternativa en el manejo de este vector. En este trabajo, se evaluó experimentalmente y describió por medio de un modelo matemático, la dinámica del control de poblaciones naturales de A. aegypti, utilizando Bti. Se determinó el perfil de susceptibilidad, a través de bioensayos dosis-respuesta con larvas colectadas de Armenia (Quindío, Colombia). Adicionalmente, con los datos de mortalidad de las localidades analizadas, un nuevo análisis fue realizado, para estimar el perfil de susceptibilidad del municipio de Armenia. Los datos de mortalidad fueron utilizados para calcular las concentraciones letales 50 y 95. Con éstas, se realizaron simulaciones hipotéticas del comportamiento del vector, obtenidas a partir de un modelo matemático, que describe la dinámica poblacional, usando aplicaciones sucesivas de Bti y diferentes intervalos de tiempo. Los bioensayos dosis-respuesta indican que las poblaciones del vector analizadas son susceptibles al Bti, por presentar una respuesta biológica similar a la obtenida en la cepa de referencia Rockefeller. Las simulaciones aplicando un control periódico sostenido, sugieren que el Bti es efectivo para controlar el vector; sin embargo, su eficiencia a largo plazo depende de la relación entre concentración letal y frecuencia de aplicación. Se concluye que la aplicación sostenida de Bti constituye una alternativa viable para el control de poblaciones de A. aegypti, a largo plazo.

ABSTRACT In Colombia, Aedes aegypti is resistant to most used insecticides. Due to the slow development of resistance to Bacillus thuringiensis var. israelensis (Bti) as well as its high specificity and environmental safety, the use of this larvicide becomes an alternative in the management of this vector. In this work, we evaluated experimentally and describe by a mathematical model the dyamics of control of natural populations of A. aegypti using Bti. The susceptibility profile to Bti was determined through dose-response bioassays with larvae collected in Armenia (Quindío, Colombia). In addition, in order to estimate the susceptibility profile, an analysis was carried out using the mortality data obtained from the four localities analyzed. The mortality data were used to estimate the lethal concentrations (LC50 and 95) from each locality. Using these LC, hypothetical simulations of vector behavior were carried out, obtained from a mathematical model that describes the population dynamics, using successive applications of Bti at different time intervals. The dose-response bioassays indicate tha the analyzed vector populations are susceptible to Bti since they present a biological response similar to the one obtained from A. aegypti Rockefeller strain. Computer simulations using sustained periodic inspection indicate Bti is effective for the vector control. Nevertheless, its long-term efficiency depends on relation between the LC and the frequency of application. It is concluded that the sustained application of Bti represents a long-term viable alternative for the control of A. aegypti populations.

Estudo experimental sobre a ação de larvicidas em populações de Aedes aegypti do município de Itabuna, Bahia, em condições simuladas de campo / Estudio experimental sobre la acción de larvicidas en poblaciones de Aedes aegypti del municipio brasileño de Itabuna, BA, en condiciones simuladas de campo / Experimental study on the action of larvicides in Aedes aegypti populations collected in the Brazilian municipality of Itabuna, Bahia, under simulated field conditions

Objetivo: avaliar, em condições simuladas de campo, a eficácia do pyriproxyfen (hormônio juvenil), do novaluron (inibidor de quitina) e do spinosad (biolarvicida) no controle do Aedes aegypti. Métodos: exposição periódica de larvas de Ae. aeypti obtidas em Itabuna a recipientes tratados com os larvicidas, e comparação do efeito residual do tratamento com cepa Rockfeller. Resultados: o efeito inibitório na emergência de adultos, após 60 dias, foi de 89,5% spinosad, 96,5% novaluron e 75,4% pyriproxifen para larvas de Itabuna, não havendo diferença estatística (p=0,412) entre os tratamentos; spinosad e novaluron apresentaram maior percentual de mortalidade na fase larval, 98,8% e 97,9% respectivamente; pyriproxifen apresentou mortalidade maior na fase pupal, 95,1%. Conclusão: os três larvicidas apresentaram controle semelhante; no entanto, o pyriproxifen pode deixar a falsa impressão de positividade dos criadouros, por agir em fase pupal, comprometendo os indicadores de infestação que são parâmetros estratégicos para as ações de controle.

Objetivo: evaluar en condiciones simuladas de campo la eficacia del piriproxifén (hormona juvenil), novaluron (inhibidor de quitina) y spinosad (biolarvicida) en el control del Ae. Aegypti. Métodos: exposición periódica de larvas obtenidas de Itabuna, BA, Brasil, a recipientes tratados con larvicida y comparación del efecto residual con cepa Rockefeller. Resultados: el efecto inhibidor en la emergencia de adultos, después de 60 días, fue de 89,5% spinosad, 96,5% novaluron y 75,4% piriproxifén para larvas de Itabuna, no habiendo diferencia estadística (p=0,412) entre los tratamientos; spinosad y novaluron presentaron mayor mortalidad en la fase larval, 98,8% y 97,9% respectivamente; piriproxifén presentó mayor mortalidad en la fase de pupa, 95,1%. Conclusión: los tres larvicidas fueron eficaces en el control de larvas de Ae. Aegypti; sin embargo, piriproxifén puede dejar falsa positividad de los criaderos, por actuar en fase de pupa, comprometiendo los indicadores de infestación, parámetros estratégicos para las acciones de control.

Objective: to evaluate, under simulated field conditions, the efficacy of pyriproxyfen (juvenile hormone), novaluron (chitin inhibitor) and spinosad (biolarvicide) in controlling Aedes aegypti. Methods: periodic exposition of Ae. aegypti larvae collected in Itabuna, BA, Brazil, to recipients treated with larvicides and comparison of residual effect of treatment with the Rockefeller strain. Results: the inhibitory effect on adult emergence after 60 days was spinosad 89.5%, novaluron 96.5% and pyriproxifen 75.4% for Itabuna larvae, with no statistical difference (p=0.412) between treatments; spinosad and novaluron had a higher percentage of mortality in the larval stage, 98.8% and 97.9% respectively; pyriproxyfen showed higher mortality (95.1%) in the pupal stage. Conclusion: the three larvicides demonstrated similar control; however, pyriprofyxen might give a false impression of breeding ground positivity as it acts at the pupal stage, compromising the indicators of infestation that are strategic parameters for control actions.

Aceites esenciales y sus componentes como una alternativa en el control de mosquitos vectores de enfermedades / Essential oils and their components as an alternative in the control of mosquito vectors of disease

Resumen Más de la mitad de la población humana está expuesta a contraer infecciones transmitidas por mosquitos. El cambio climático y la aparición de cepas resistentes a los insecticidas tradicionalmente utilizados han motivado la búsqueda de nuevos agentes capaces de controlar las poblaciones de mosquitos. Los aceites esenciales han resultado ser eficaces agentes repelentes y larvicidas. El objetivo de este trabajo fue revisar las investigaciones llevadas a cabo en los últimos años sobre la actividad larvicida de los aceites esenciales y sus componentes contra mosquitos de los géneros Aedes, Anopheles y Culex, así como los últimos reportes sobre su posible mecanismo de acción.

Abstract More than half of the human population is exposed to mosquito-borne infections. Climate change and the emergence of strains resistant to traditionally used insecticides have motivated the search of new agents for mosquito population control. Essential oils have been effective repellents and larvicidal agents. The aim of this work was to review research studies conducted in recent years on the larvicidal activity of essential oils and their components against Aedes, Anopheles and Culex mosquitoes, as well as the latest reports about their possible mechanism of action.

Acción larvicida de extractos alcohólicos de semilla de Annona Muricata (guanábana) sobre Aedes Aegypti y Aedes Albopictus / Larvicidal action of alcoholic extracts of the seed of Annona Muricata (soursop) on Aedes Aegypti y Aedes Albopictus

Cada vez es más frecuente el reporte de resistencia de diferentes especies de vectores a los insecticidas usados en los programas de control; por ello existe un interés creciente en el desarrollo de productos eficaces, económicos y más amigables con el medio ambiente que permitan el control de los vectores de enfermedades como el dengue. Los extractos crudos obtenidos a partir de diferentes plantas han demostrado poseer actividades larvicidas. El objetivo de esta investigación fue evaluar la actividad larvicida de dos extractos alcohólicos (etanólico y metanólico) obtenidos a partir de las semillas de Annona muricata (guanábana) sobre Ae. aegypti (cepa Rockefeller) y Ae. albopictus exponiéndolas durante 24 h a diferentes diluciones de cada extracto. Las concentraciones letales (CL50) fueron las siguientes: a) para Ae. aegypti 41,8 mg L-1 (LC0,95=34,5-49,2 mg L-1) con el extracto etanólico y 32,8 mg L-1 (LC0,95=27,4-38,4 mg L-1) con el extracto metanólico; y b) para Ae. albopictus 299,6 mg L-1 (LC0,95=224,9-377,3 mg L-1) con el extracto etanólico y 326,1 mg L-1 (LC0,95=209,5-442,4 mg L-1) con extracto metanólico. El análisis de los resultados demostró que el efecto tóxico de ambos extractos sobre las larvas de Aedes fue similar y depende de la especie y de la concentración utilizada. Los resultados apuntan a que los extractos alcohólicos obtenidos a partir de A. muricata son una alternativa para el control de las especies de Aedes presentes en Venezuela.

Reports of resistance of different species of vectors to insecticides used in control programs are every time more frequent. Therefore, there is a growing interest to control harmful vectors (that transmit diseases such as dengue) by developing products that are effective, economical and environment friendly. Crude extracts obtained from different plants have demonstrated larvicidal activities. The objective of this research was to evaluate the larvicidal activity of two alcoholic extracts (ethanol and methanol) obtained from the seeds of Annona muricata (soursop) on Ae. aegypti (strain Rockefeller) and Ae. albopictus, exposed for 24 h to different dilutions of each extract. Lethal concentrations (LC50) were as follows: a) For Ae. aegypti 41.8 mg L-1 (LC0.95 =34.5 to 49.2 mg L-1) with ethanolic extract and 32.8 mg L-1 (LC0.95 =27.4 to 38.4 mg L-1) with methanolic extract; and b) For Ae. albopictus 299.6 mg L-1 (LC0.95=224.9 to 377.3 mg L-1) with ethanolic extract and =326.1 mg L-1 (LC0.95=209.5 to 442.4 mg L-1) with methanolic extract. The analysis of the results showed that the toxic effect of both alcoholic extracts on Aedes was similar and depends on the species and the concentration used. The results suggest that the alcoholic extracts obtained from A. muricata are an alternative for control of Aedes species present in Venezuela.

O uso de larvicidas em água potável é seguro? / Is the use of larvicides in drinking water safe? / ¿El uso de lavicida en la agua potable es seguro?

Provavelmente sim. Não existem evidências que comprovem a segurança do uso de larvicidas em água potável. Entretanto, os poucos estudos que existem avaliando o efeito em população de mamíferos, assim como as avaliações de biodisponibilidades e citotoxicidade, demonstram que em baixa concentração são seguros e não há efeitos carcinogênicos ou genotóxico. Os larvicidas avaliados e autorizados para uso em água potável pela Organização Mundial de Saúde, destinada para consumo humano são: DIFLUBENZUROM, METOPRENO, NOVALUROM, Pirimifós/, PIRIPROXIFEM, ESPINOSADE, TEMEFÓS, além do Bacillus thuringiensis israelensis (BTI). Recomenda-se sempre usar a dose correta dos larvicidas. O temephós é utilizado para tratamento de focos, mas não deve ser utilizado em aquários com peixes. Aprovado para uso em água de consumo humano. O pyriproxyfen é um éter e não há evidências que comprovem que cause dano em fetos de mamíferos. BTI é recomendado como larvicida para uso em saúde pública, é uma bactéria que em contato com a água libera substâncias tóxicas para as larvas de alguns insetos. A aplicação deverá ser realizada por profissional treinado. O BTI não apresenta ingesta diária aceitável, entretanto a orientação de uso deve ser de 1-5mg/litro. A avaliação de substâncias químicas de qualquer natureza sempre deve salientar a possibilidade de bioacumulação. As substâncias que não são biodegradadas, são biopersistentes e mantêm-se em altas quantidades nos tecidos dos seres vivos. Portanto, mesmo que as substâncias não sejam para consumo humano direto a avaliação do seu uso na agricultura, leito de rio e pastos deve ser avaliada criteriosamente.

Probably yes. There is no evidence to prove the safety of the use of larvicides in drinking water. However, there are few studies evaluating the effect on the population of mammals, as are the bioavailabilities and cytotoxicity reviews show that in low concentrations are safe and no genotoxic or carcinogenic effects. Larvicides evaluated and authorized for use in drinking water by the World Health Organization, intended for human consumption are: DIFLUBENZUROM, METOPRENO, NOVALUROM, Pirimifós/, PIRIPROXIFEM, ESPINOSADE, TEMEFÓS, beyond Bacillus thuringiensis israelensis (BTI). It is recommended to always use the correct dose of larvicides. Temephos is used to treat outbreaks, but should not be used in fish tanks. Approved for use in drinking water. The pyriproxyfen is an ether and there is no evidence to support that it causes damage in mammalian fetuses. BTI are recommended as larvicides for use in public health, it is a bacterium that contact with water releases toxic to the larvae of some insects. The application should be performed by trained professional. BTI has no acceptable daily intake, however the guidance of use should be 1-5mg/liter. The evaluation of chemicals of any kind should always stress the possibility of bioaccumulation. Substances that are not biodegraded are biopersistent and remain at high levels in the tissues of living things. So even if the substances are not for direct human consumption, an appraisal of its use in agriculture, river bed and pastures should be carefully evaluated.

Probablemente sí. No hay evidencia para demostrar la seguridad del uso de larvicidas en la agua potable. Sin embargo, hay pocos estudios que evalúan el efecto sobre la población de mamíferos, como son los biodisponibilidad y las revisiones de citotoxicidad muestran que en concentraciones bajas son seguros y sin efectos genotóxicos o cancerígenos. Larvicidas evaluadas y autorizadas para su uso en la agua potable por la Organización Mundial de Salud, destinados al consumo humano son: DIFLUBENZUROM, METOPRENO, NOVALUROM, Pirimifós/, PIRIPROXIFEM, ESPINOSADE, TEMEFÓS, más allá de Bacillus thuringiensis israelensis (BTI). Se recomienda utilizar siempre la dosis correcta de larvicidas. Temephos se utiliza para tratar los brotes, pero no se debe utilizar en los tanques de peces. Aprobado para uso en la agua potable. El piriproxifeno es un éter y no hay evidencia para apoyar que causa daños en los fetos de mamíferos. Se recomienda BTI como larvicida para uso en la salud pública, es una bacteria que en contacto con el agua tóxicas para las larvas de algunos insectos. La aplicación debe ser realizada por profesionales capacitados. BTI no tiene ninguna ingesta diaria admisible, sin embargo, la orientación de uso debe ser 1-5 mg/litro. La evaluación de los productos químicos de cualquier tipo siempre se debe hacer hincapié en la posibilidad de bioacumulación. Las sustancias que no se biodegradan, son biopersistente y se mantienen en niveles altos en los tejidos de los seres vivos. Así que incluso si las sustancias no son para el consumo humano directo, una apreciación de su uso en la agricultura, lecho del río y pastos debe ser cuidadosamente evaluada.

Insecticide susceptibility in larval populations of the West Nile vector Culex pipiens L. (Diptera: Culicidae) in Saudi Arabia

Objective: To investigate the susceptibility to some conventional and non-conventional insecticides in laboratory and field larval populations of the West Nile vector Culex pipiens L. (Cx. pipiens), the dominant species in Jeddah Province, Saudi Arabia. Methods: The tested conventional insecticides were Actikil and Pesgard, while the non-conventional ones were Bacilod, Dudim and Baycidal. Probit analysis and photomicroscopical observations were carried out to shed light on acute toxicity in laboratory and field Cx. pipiens strains. Results: Cx. pipiens were more susceptible to Pesgard (LC

Larvicidal activities of hydro-ethanolic extracts of three Cameroonian medicinal plants against Aedes albopictus

Objective To investigate the larvicidal activity of Syzygium guineense (Myrtaceae) (S. guineense), Monodora myristica and Zanthoxylum heitzii (Rutaceae) (Z. heitzii) extracts against Aedes albopictus (Ae. albopictus). Methods The larvicidal activity of the hydro-ethanolic extracts from these plant species was assessed at three different concentrations (50, 100 and 200 mg/L) on first-instar of Ae. albopictus larvae in comparison with untreated controls. Mortality rate was recorded daily for a period of 12 days. The values of LC

Larvicidal activities of hydro-ethanolic extracts of three Cameroonian medicinal plants against Aedes albopictus

Objective: To investigate the larvicidal activity of Syzygium guineense (Myrtaceae) (S. guineense), Monodora myristica and Zanthoxylum heitzii (Rutaceae) (Z. heitzii) ex-tracts against Aedes albopictus (Ae. albopictus). Methods: The larvicidal activity of the hydro-ethanolic extracts from these plant species was assessed at three different concentrations (50, 100 and 200 mg/L) on first-instar of Ae. albopictus larvae in comparison with untreated controls. Mortality rate was recorded daily for a period of 12 days. The values of LC50 and lethal time killing 50%of the tested individuals (LT50) were calculated using the log-probit analysis. Results: The root extract of S. guineense exhibited the best activity with 100%mortality after 8 days of treatment at 200 mg/L, followed by the fruit extract of Z. heitzii with 83.33%mortality at the same concentration. Nonetheless, larvae were most susceptible to the fruit extract of Z. heitzii both in terms of LC50 (39.89 mg/L) and LT50 (145.68 h). A statistically significant difference between the control and the group treated at 200 mg/L was noticed in all the extracts. Conclusions: The present study shows that the hydro-ethanolic extracts of S. guineense, Monodora myristica and Z. heitzii tested have significant larvicidal activity. These pre-liminary results are of great interest and some of these plant species can be proposed for the formulation of new bioinsecticides to control Ae. albopictus populations.

Insecticide susceptibility in larval populations of the West Nile vector Culex pipiens L. (Diptera:Culicidae) in Saudi Arabia

Objective: To investigate the susceptibility to some conventional and non-conventional insecticides in laboratory and field larval populations of the West Nile vector Culex pipiens L. (Cx. pipiens), the dominant species in Jeddah Province, Saudi Arabia. Methods: The tested conventional insecticides were Actikil and Pesgard, while the non-conventional ones were Bacilod, Dudim and Baycidal. Probit analysis and photo-microscopical observations were carried out to shed light on acute toxicity in laboratory and field Cx. pipiens strains. Results: Cx. pipiens were more susceptible to Pesgard (LC50: 0.045 and 0.032 mg/L) than Actikil (0.052 and 0.038 mg/L) and Bacilod (0.129 and 0.104 mg/L), for the field and laboratory strains, respectively. Results showed that treatments with the chitin syn-thesis inhibitor Dudim and Baycidal evoked morphological effects similar to those induced by other insect growth regulators. According to IC50 values obtained (concen-tration which to inhibit the emergence of 50%of mosquito adults), the compound Dudim (0.000 3 and 0.000 1 mg/L) was more effective against Cx. pipiens L. mosquitoes than Baycidal (0.000 4 and 0.000 3 mg/L) for both the field and laboratory strains, respectively. Conclusions: Our results provide baseline data to enhance control programs and orient public health decisions on the selection of pesticides against mosquito vectors in Saudi Arabia.

Larvicidal efficacies and chemical composition of essential oils of Pinus sylvestris and Syzygium aromaticum against mosquitoes

Objective:To assess the chemical composition and mosquito larvicidal potentials of essential oils of locally sourced Pinus sylvestris (P. sylvestris) and Syzygium aromaticum (S. aromaticum) against Aedes aegypti (A. aegypti) and Culex quinquefasciatus (C. quinquefasciatus). Method:The chemical composition of the essential oils of both plants was determined using GC-MS while the larvicidal bioassay was carried out using different concentrations of the oils against the larvae of A. aegypti and C. quinquefasciatus in accordance with the standard protocol. Results:The results as determined by GC-MS showed that oil of S. aromaticum has eugenol (80.5%) as its principal constituent while P. sylvestris has 3-Cyclohexene-1-methanol, .alpha., .alpha.4-trimethyl (27.1%) as its dominant constituent. Both oils achieved over 85%larval mortality within 24 h. The larvae of A. aegypti were more susceptible to the oils [LC50 (S. aromaticum)=92.56 mg/L, LC50(P. sylvestris)=100.39 mg/L] than C. quinquefasciatus [LC50(S. aromaticum)=124.42 mg/L;LC50(P. sylvestris)=128.00 mg/L]. S. aromaticum oil was more toxic to the mosquito larvae than oil of P. sylvestris but the difference in lethal concentrations was insignificant (P>0.05). Conclusion: The results justify the larvicidal potentials of both essential oils and the need to incorporate them in vector management and control.

In vitro PHYTOTHERAPY OF VECTOR SNAILS BY BINARY COMBINATIONS OF LARVICIDAL ACTIVE COMPONENTS IN EFFECTIVE CONTROL OF FASCIOLIASIS / Fitoterapia in vitro de caramujos vetores por combinações binárias de componentes ativos larvicidas como controle efetivo de fasciolíase

SUMMARY A food-borne trematode infection fascioliasis is one among common public health problems worldwide. It caused a great economic loss for the human race. Control of snail population below a certain threshold level is one of the important methods in the campaign to reduce the incidence of fascioliasis. The life cycle of the parasite can be interrupted by killing the snail or Fasciola larva redia and cercaria inside of the snail Lymnaea acuminata. In vitro toxicity of different binary combinations (1:1 ratio) of plant-derived larvicidal active components such as citral, ferulic acid, umbelliferone, azadirachtin and allicin against Fasciola redia and cercaria were tested. The mortality of larvae was observed at 2h, 4h, 6h and 8h of treatment. In in vitro condition azadirachtin + allicin (1:1 ratio) was highly toxic against redia and cercaria (8h LC50 0.006 and 0.005 mg/L). Toxicity of citral + ferulic acid was lowest against redia and cercaria larvae. .

RESUMO A infecção alimentar pelo trematóide da fasciolíase é uma dentre os mais comuns problemas de saúde pública mundiais, causando grande prejuízo econômico para a humanidade. Controle da população de caramujos abaixo de determinado nível é um dos métodos no campo mais importantes para a redução da incidência da fasciolíase. O ciclo de vida do parasita pode ser interrompido pela morte do caramujo ou da larva redia e cercária da Fasciola dentro da Lymnaea acuminata. Foi testada a toxicidade in vitro das diferentes combinações binárias (relação 1:1) entre os vários componentes larvicidas ativos da planta tais como citral, ácido ferúlico, umbeliferone, azadiractina, e alicina contra a Fasciola redia e a cercária. A mortalidade das larvas foi observada após duas, quatro, seis e oito horas de tratamento. A condição in vitro azadiractina + alicina (relação 1:1) foi altamente tóxica contra redia e cercária (8h LC50 0,006 e 0,005 mg/L). Toxicidade do citral + ácido ferúlico foi a mais baixa contra redia e larvas de cercária. .

Larvicidal activity of Kotschya uguenensis plant powders and methanol extracts against Anopheles gambiae s.s. larvae in the laboratory and in simulated ponds.

Polar constituents of Kotschya uguenensis Verdc. (Fabaceae) do not exhibit acute toxicity but cause growth disruption of Anopheles gambiae s.s. Gile (Diptera: Culicidae) larvae with eventual death. Time-course larvicidal effects of powders of root and stem barks and their crude methanol extracts in form of emulsions were compared in the laboratory and in artificial semi-field ponds. Kotschya uguenensis powders of root and stem barks and emulsions of their crude methanol extracts were assayed against An. gambiae s.s according to protocols of WHO 1996 & 2005. All formulations were equally effective under laboratory conditions giving 100% larval mortality within three days at a dose of 50 μg/ml of the extracts or concentrations of powders corresponding to the same level of extractable material. Under semi-field conditions, suspensions of the powder materials appeared to perform better than emulsions of methanol extracts. Time taken to give 80% mortality (LT80) of larvae and pupa at 0.1% w/v was 6.06 days for powders of root bark and 5.60 days for powders of stem bark. The LT80 for the root bark extract at 200 μg/ml was 8.28 days while that for the stem bark methanol extract was 12.47 days. No residual effects of the test materials on the larvae or pupae were evident in semi-field ponds 14 days after the reintroduction of the test materials. Our results suggest that, for the control of anophelines in the field, a weekly application of appropriate amounts of powders of K. uguenensis may be effective.

Actividad larvicida de extractos etanólicos de Tabernaemontana cymosa y Trichilia hirta sobre larvas de estadio III y IV de Aedes aegypti (Diptera: Culicidae) / Larvicidal activity of ethanol extracts of Tabernaemontana cymosa and Trichilia hirta against III and IV stage larvae of Aedes aegypti (Diptera: Culicidae)

Introducción: el mosquito Aedes aegypti es el principal vector de los virus del dengue y la fiebre amarilla. Una de las formas actuales para combatir estas enfermedades es el control del vector. Sin embargo, los problemas causados por los insecticidas sintéticos y la resistencia adquirida por los mosquitos, hacen cada vez más difícil esta lucha. Las plantas constituyen una fuente alternativa al uso de insecticidas sintéticos. Objetivos: evaluar la actividad larvicida para el mosquito Aedes aegypti, de los extractos etanólicos y fracciones activas, de diferentes órganos vegetales de las especies Trichilia hirta L. y Tabernaemontana cymosa Jacq. Métodos: en este estudio se utilizaron larvas de Aedes aegypti en estadios III y IV. Los extractos etanólicos totales se obtuvieron por maceración del material vegetal seco y molido, durante una semana y posterior secado a presión reducida con un rotoevaporador. La obtención de fracciones y subfracciones, se realizó por cromatografía de columna abierta, usando solventes de diferentes polaridades. La actividad larvicida se evaluó bajo protocolos recomendados por la Organización Mundial de la Salud. Resultados: los extractos etanólicos de corteza de Trichilia hirta y flores, corteza y hojas de Tabernaemontana cymosa, no mostraron actividad larvicida. El extracto de semillas de Trichilia hirta mostró una actividad moderada con una CL50 y CL90 de 219,2 y 331,4 mg/L respectivamente. El extracto etanólico de semillas de Tabernaemontana cymosa, la fracción F008 y la subfracción F011, mostraron una buena actividad larvicida con CL50 de 35,1; 20,9, y 14,98 mg/L, respectivamente. Conclusiones: según los resultados, se consideró como promisorio el extracto de semillas de Tabernaemontana cymosa para la obtención de metabolitos secundarios con actividad larvicida.

Introduction: Aedes aegypti is the main vector of dengue and yellow fever. One way to combat these diseases today is the vector control. However, the problems caused by synthetic insecticides and the acquired resistance by mosquitoes, turn this control into a more difficult struggle every day. The plants offer an alternative source to the use of synthetic insecticides. Objectives: the objective of this study was to evaluate the larvicidal activity of the ethanol extracts and active fractions of different organs of Trichilia hirta L. and Tabernaemontana cymosa Jacq. Methods: in this study, Aedes aegypti larvae in III and IV stages were used. The total ethanol extracts were obtained by maceration of dried and ground plant material for a week and then dried at reduced pressure. The fractionation was performed by open column chromatography with the use of different polarity solvents. The larvicidal activity was assessed following protocols recommended by the World Health Organization. Results: the ethanol extracts from Trichilia hirta bark and flowers, and Tabernaemontana cymosa bark and leaves showed no larvicidal activity. The Trichilia hirta seed extract showed a moderate activity with an LC50 and LC90 of 219.2 and 331.4 mg/L respectively. The ethanol extract from Tabernaemontana cymosa seeds, the fraction F008 and the subfraction F011, showed good larvicidal activity with LC50 of 35.1, 20.9, and 14.98 mg/L, respectively. Conclusions: according to the results obtained in this study, the extract from Tabernaemontana cymosa seeds could be considered as a potential source of secondary metabolites with larvicidal activity.

Plant extracts as potential mosquito larvicides.

Mosquitoes act as a vector for most of the life threatening diseases like malaria, yellow fever, dengue fever, chikungunya ferver, filariasis, encephalitis, West Nile Virus infection, etc. Under the Integrated Mosquito Management (IMM), emphasis was given on the application of alternative strategies in mosquito control. The continuous application of synthetic insecticides causes development of resistance in vector species, biological magnification of toxic substances through the food chain and adverse effects on environmental quality and non target organisms including human health. Application of active toxic agents from plant extracts as an alternative mosquito control strategy was available from ancient times. These are non-toxic, easily available at affordable prices, biodegradable and show broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on phytochemical sources and mosquitocidal activity, their mechanism of action on target population, variation of their larvicidal activity according to mosquito species, instar specificity, polarity of solvents used during extraction, nature of active ingredient and promising advances made in biological control of mosquitoes by plant derived secondary metabolites have been reviewed.

Efficacy of Five Mosquito Larvicides Against Mosquito Larvae in Field / 环境与健康杂志

malathion.68 days after chlopyrifos was sprayed,the decrease rate of larvae density was still 95.34%.Conclusion The efficacy and persistent activity of chlopyrifos and the mixture of Bti and Bs-10 against mosquito larvae was better than the others.To control mosquito larvae in field,the suitable larvicides and application dosages should be applied according to the environment,characteristics,the pollute condition of water body etc.