Óleos essenciais e extratos vegetais como ferramentas alternativas ao controle químico de larvas de Aedes spp, Anopheles spp e Culex spp / Essential oils and plant extracts as alternative tools for chemical control of Aedes spp, Anopheles spp, and Culex spp

Objetivos: Realizar um levantamento das contribuições científicas produzidas entre 2017 e 2021 acerca do efeito larvicida de óleos essenciais e extratos vegetais no controle de Aedes spp, Anopheles spp e Culex spp. Métodos: de setembro a outubro de 2022, foi realizado um levantamento de artigos científicos publicados entre os anos de 2017 e 2021, nas bases de dados Portal Periódicos Capes, Scielo, Science Direct e Scopus. Foram utilizados os descritores "larvicide", "essential oil" e "plant extracts" com a interposição do operador boleano "AND". Resultados: inicialmente, foram obtidos 246 artigos, dos quais 110 foram excluídos (68 não estavam disponíveis na íntegra e 42 apareceram em mais de uma base de dados). Dos 136 artigos restantes, 36 foram excluídos por não terem realizado ensaio larvicida. Dos 100 artigos remanescentes, 63 foram excluídos por não mencionarem valores de CL50, enquanto 3 não especificaram a estrutura vegetal de obtenção dos produtos naturais, restando, portanto, 34 artigos para análise. Foram utilizadas 57 espécies vegetais para a obtenção dos produtos vegetais utilizados contra larvas de Aedes spp; 11 espécies nos ensaios contra Anopheles spp, e 36 espécies nos ensaios contra Culex spp. Os óleos essenciais predominaram nos ensaios contra Aedes spp, enquanto os extratos, contra Anopheles spp. A maior parte dos produtos testados exibiu CL50 < 100 ppm. Conclusão: a atividade larvicida demonstrada por uma grande variedade de extratos vegetais e óleos essenciais representa uma alternativa promissora ao tradicional controle químico feito à base de inseticidas sintéticos em programas de manejo integrado de vetores.

Objectives: Conduct a survey of the scientific contributions produced between 2017 and 2021 on the larvicidal effect of essential oils and plant extracts in the control of Aedes spp, Anopheles spp, and Culex spp. Methods: from September to October 2022, a survey was carried out of scientific articles published between 2017 and 2021 in the Portal Periódicos Capes, Scielo, Science Direct, and Scopus databases. The descriptors "larvicide", "essential oil" and "plant extracts" were used with the Boolean operator "AND". Results: initially, 246 articles were obtained, of which 110 were excluded (68 were not available, and 42 appeared in more than one database). Of the remaining 136 articles, 36 were excluded because they did not perform a larvicide assay. Of the 100 remaining articles, 63 were excluded for not mentioning LC50 values, while three did not specify the plant structure for obtaining natural products, thus leaving 34 articles for analysis. A total of 57 plant species were used to obtain plant products used against Aedes spp larvae; 11 species in the tests against Anopheles spp, and 36 species in the tests against Culex spp. Essential oils predominated in the tests against Aedes spp, while extracts against Anopheles spp. Most of the products tested exhibited an LC50 < 100 ppm. Conclusion: the larvicidal activity demonstrated by a wide variety of plant extracts and essential oils represents a promising alternative to traditional chemical control based on synthetic insecticides in integrated vector management programs.

Chemical composition and larvicidal activity of essential oils from Zingiber montanum (J. Koenig) Link ex. A. Dietr. against three mosquito vectors / Composición química y actividad larvicida de aceites esenciales de Zingiber montanum (J. Koenig) Link ex. A. Dietr. contra tres vectores de mosquitos

The chemical composition and larvicidal activity of essential oils derived from the leaves and rhizomes of Zingiber montanum (J. Koenig) Link ex. A. Dietr. were reported. The main compounds in the leaf oil were ß-pinene (13.8%), ß-phellandrene (11.3%) and α-pinene (7.3%) while the rhizome oil was dominated by sabinene (41.1%), terpinen-4-ol (22.7%) and (E)-nerolidol (14.3%). The minimum lethal concentration (larvicidal activity) LC50of the rhizome oil at 24 h against Aedes albopictus was 35.17 µg/mL, while LC50 values of 32.20 µg/mL and 31.12 µg/mL were obtained against Aedes aegypti and Culex quinquefasciatus respectively. At 48 h the oil displayed larvicidal action with LC50 values of 23.18 µg/mL, 25.58 µg/mL and 18.99 µg/mL respectively towards Ae. albopictus, Ae. Aegyptiand Cx. quinquefasciatus. The leaf oil did not exhibit significant mortality and larvicidal action. The results indicate the potential of rhizome essential oil of Z. montanumas a source of larvicidal agent.

En el presente trabajo se reportan la composición química y actividad larvicida de los aceites esenciales obtenidos de hojas y rizomas de Zingiber montanum (J. Koenig) Link ex. A. Dietr. Los principales compuestos en el aceite de hojas fueron ß-pineno (13.8%), ß-felandrene (11.3%) y α-pineno (7.3%); mientras que los más abundantes en el aceite de rizomas fueron sabineno (41.1%), terpinen-4-ol (22.7%) y (E)-nerolidol (14.3%). La concentración letal mínima (actividad larvicida) LC50 del aceite de riomas ante Aedes albopictus fue 35.17 µg/mL, mientras que los valores de LC50 de 32.20 µg/mL y 31.12 µg/mL fueron obtenidos ante Aedes aegyptiy Culex quinquefasciatus respectivamente. A las 48 horas, el aceite mostró acción larvicida con valores de LC50 de 23.18 µg/mL, 25.58 µg/mL y 18.99 µg/mL respectivamente, ante Ae. albopictus, Ae. Aegyptiand Cx. quinquefasciatus. El aceite de hojas no mostró mortalidad ni acción larvicida significativa. Los resultados indican el potencial del aceite esencial de rizomas de Z. montanum como una fuente de agentes larvicidas.

Evaluation of the larvicidal potential of root and leaf extracts of Saussurea costus (Falc. ) Lipsch. against three mosquito vectors: Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus

Abstract INTRODUCTION: The larvicidal potential of Saussurea costus (Falc.) Lipsch. was studied against the early 4th instar larvae of Anopheles stephensi Liston., Aedes aegypti Linn.,and Culex quinquefasciatus Say. because of the emergence of mosquito resistance to conventional synthetic insecticides. METHODS: At concentrations of 12.5-200 ppm, larvicidal activities were studied under laboratory conditions. RESULTS: After 24 h of exposure, the methanol extract of the roots recorded the highest larvicidal activity against An. stephensi, with LC50 and LC90values of 7.96 and 34.39 ppm, respectively. CONCLUSIONS: We are developing potent larvicidal compound(s) from S. costus for controlling the mosquito larval population.

Larvicidal effect of Clinopodium macrostemum essential oil extracted by microwave-assisted hydrodistillation against Culex quinquefasciatus (Diptera: Culicidae)

Abstract INTRODUCTION: In the present study, we determined the chemical composition of Clinopodium macrostemum essential oil obtained by microwave-assisted hydrodistillation and its effect on the growth and development of Culex quinquefasciatus mosquito larvae. METHODS: The essential oil compounds were identified by gas chromatography-mass spectrometry analysis, and bioassays were conducted to evaluate the influence on the developmental stages of early second instar larvae of Cx. quinquefasciatus until the emergence of adults, using essential oil concentrations of 50, 100, 200, 400, and 800mg/L. RESULTS: The gas chromatography-mass spectrometry analyses revealed that the leaf essential oil of C. macrostemum contained 32 compounds and the major chemical compounds identified were linalool (55.4%), nerol (6.4%), caryophyllene (6.25%), menthone (5.8%), geraniol acetate (4.1%), terpineol (3.7%), and pulegone (2.8%). The essential oil yield obtained by microwave-assisted hydrodistillation was 0.8% at 20 min. The treatments showed lethal concentrations (LC50 and LC90) of 22.49 and 833.35mg/L, respectively, after the final measurement of the total number of dead larvae (second, third, and fourth instars), and LC50 and LC90 of 6.62 and 693.35mg/L, respectively, at the end of the experimental period. The essential oil inhibited the growth and development of the mosquito larvae by 32% (relative growth index = 0.68) at 50mg/L, and up to 47% (relative growth index = 0.53) at 800mg/L. CONCLUSION: The present study demonstrated the larvicidal effect of C. macrostemum essential oil on Cx. quinquefasciatus, which can be attributed to the oxygenate compounds obtained by the extraction method.

Larvicidal activity of crude extracts from Larrea cuneifolia (Zygophyllaceae) and of its metabolite nordihydroguaiaretic acid against the vector Culex quinquefasciatus (Diptera: Culicidae)

INTRODUCTION: The aim of the present study was to analyze the larvicidal activity of different crude extracts of Larrea cuneifolia and its most abundant lignan, nordihydroguaiaretic acid (NDGA), against Culex quinquefasciatus. METHODS: Chloroform, methanol, and aqueous extracts from L. cuneifolia and NDGA were tested against larvae of Cx. quinquefasciatus under laboratory conditions. RESULTS: The chloroform extract showed the highest larvicidal effect, with an estimated LC50 of 0.062 mg/ml. NDGA also demonstrated significant larvicidal activity with an estimated LC50 of 0.092 mg/ml. CONCLUSIONS: These results indicate that the chloroform extract of L. cuneifolia and NDGA are promising insecticides of botanical origin that could be useful for controlling Cx. quinquefasciatus.

Larvicidal effect of aqueous and ethanolic extracts of Senna alata on Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti

Senna alata is locally used in South Eastern Nigeria in the treatment of several infections which include ringworm and other parasitic skin diseases.The larvicidal activities of aqueous and ethanolic leaf and stem extracts of S. alata were evaluated in static bioassays, on fourth instar larvae of Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti, at extract concentrations of 0.15, 0.30, 0.45, 0.60 and 0.75% w/v, for 72 hours. Mortality of larvae exposed to the different extracts increased with increase in extract concentration and time of exposure. This study revealed a differential potency of the extracts used and a difference in susceptibility of larvae to the extracts as evident by the 72hLC[50] values obtained. The leaf extract proved to be more lethal to the larvae than the stem extract as judged by the 72hLC[50] values obtained both for the aqueous as well as the ethanolic extracts assayed. Phytochemical screening of the plant parts investigated revealed the presence of some plant metabolites, which have been reported in separate studies to be lethal to mosquito larvae. Results obtained from this study suggest that the leaf and stem extracts of S. alata possess a promising larvicidal potential which can be exploited in mosquito vector control

Evaluation of toxicity of plant extracts against vector of lymphatic filariasis, Culex quinquefasciatus.

Background & objectives: Conventional insecticides are generally used as larvicides to control Culex quinquefasciatus, vector of lymphatic filariasis. This study was undertaken to evaluate the larvicidal activity of some potential larvicidal plants leaf extracts against Cx. quinquefasciatus larvae. Methods: The toxic effects of petroleum ether leaf extracts of plants viz., Argemone mexicana (Mexican prickly poppy), Clausena dentata (Dentate), Cipadessa baccifera (Rana bili), Dodonaea angustifolia (Hop bush) and Melia dubia (Pride of India) were evaluated under laboratory conditions in individual and in combination against 3rd - 4th instar larvae of Cx. quinquefasciatus. Results: The results indicated that among the selected plants, A. mexicana showed maximum larvicidal activity with an LC50 value of 48.89 ppm. Its toxicity was enhanced when the extract was mixed (1:1) with that of C. dentata as the LC50 value became 28.60 ppm indicating synergistic action of A. mexicana. Interpretation & conclusions: Our results showed high larvicidal potential in A. mexicana leaf extract, and it also showed additive effect when mixed with C. dentata extract.

Treatment of an Aedes aegypti colony with the Cry11Aa toxin for 54 generations results in the development of resistance

To study the potential for the emergence of resistance in Aedes aegypti populations, a wild colony was subjected to selective pressure with Cry11Aa, one of four endotoxins that compose the Bacillus thuringiensis serovar israelensis toxin. This bacterium is the base component of the most important biopesticide used in the control of mosquitoes worldwide. After 54 generations of selection, significant resistance levels were observed. At the beginning of the selection experiment, the half lethal concentration was 26.3 ng/mL and had risen to 345.6 ng/mL by generation 54. The highest rate of resistance, 13.1, was detected in the 54th generation. Because digestive proteases play a key role in the processing and activation of B. thuringiensis toxin, we analysed the involvement of insect gut proteases in resistance to the Cry11Aa B. thuringiensis serovar israelensis toxin. The protease activity from larval gut extracts from the Cry11Aa resistant population was lower than that of the B. thuringiensisserovar israelensis susceptible colony. We suggest that differences in protoxin proteolysis could contribute to the resistance of this Ae. aegypti colony.

Larvicidal activity of medicinal plant extracts against Anopheles subpictus & Culex tritaeniorhynchus.

Background & objectives: Mosquitoes transmit serious human diseases, causing millions of deaths every year and the development of resistance to chemical insecticides resulting in rebounding vectorial capacity. Plants may be alternative sources of mosquito control agents. The present study assessed the role of larvicidal activities of hexane, chloroform, ethyl acetate, acetone, and methanol dried leaf and bark extracts of Annona squamosa L., Chrysanthemum indicum L., and Tridax procumbens L. against the fourth instar larvae of malaria vector, Anopheles subpictus Grassi and Japanese encephalitis vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae). Methods: Larvicidal activities of three medicinal plant extracts were studied in the range of 4.69 to 1000 mg/l in the laboratory bioassays against early 4th instar larvae of An. subpictus and Cx. tritaeniorhynchus. The mortality data were subjected to probit analysis to determine the lethal concentrations (LC50 and LC90) to kill 50 and 90 per cent of the treated larvae of the respective species. Results: All plant extracts showed moderate effects after 24 h of exposure; however, the highest toxic effect of bark methanol extract of A. squamosa, leaf ethyl acetate extract of C. indicum and leaf acetone extract of T. procumbens against the larvae of An. subpictus (LC50 = 93.80, 39.98 and 51.57 mg/l) and bark methanol extract of A. squamosa, leaf methanol extract of C. indicum and leaf ethyl acetate extract of T. procumbens against the larvae of Cx. tritaeniorhynchus (LC50 =104.94, 42.29 and 69.16 mg/l) respectively. Interpretation & Conclusions: Our data suggest that the bark ethyl acetate and methanol extract of A. squamosa, leaf ethyl acetate and methanol extract of C. indicum, acetone and ethyl acetate extract of T. procumbens have the potential to be used as an ecofriendly approach for the control of the An. subpictus, and Cx. tritaeniorhynchus.

Development of a controlled release formulation of an indigenous insect growth regulator, DPE-28, a substituted diphenylether, for controlling the breeding of Culex quinquefasciatus.

Background & objectives: DPE-28, a substituted diphenyl ether (2,6-ditertiarybutyl phenyl-2’,4’-dinitro phenyl ether) was reported to exhibit promising insect growth regulating activity against Culex quinquefasciatus, the vector of lymphatic filariasis. A controlled release formulation (CRF) of DPE-28 has been developed to control Cx. quinquefasciatus in its breeding habitats. Toxicity of DPE-28, safety to non-target mosquito predators and the release profile of the CRF of DPE-28 are studied and discussed. Methods: The acute oral and dermal toxicity was tested in male and female Wistar rats as per the Organization for Economic Cooperation and Development (OECD) guidelines 425 and 402 respectively. The toxicity of DPE-28 to non-target predators was tested as per the reported procedure from this laboratory. The CRF of DPE-28 was prepared by following the reported procedure developed at this laboratory earlier. The concentration of DPE-28 released from the CRF was monitored by HPLC by constructing a calibration graph by plotting the peak area in the Y-axis and the concentration of DPE-28 in the X-axis. Results: DPE-28 has been tested for acute oral toxicity and found to be moderately toxic with LD50 value of 1098 mg/kg body weight (b.w). The results of the acute dermal toxicity and skin irritation studies reveal that DPE-28 is safe and non-irritant. DPE-28 when tested at 0.4 mg/litre against non-target mosquito predators did not produce any mortality. The release profile of the active ingredient DPE-28 from the CRF by HPLC technique showed that the average daily release (ADR) of DPE-28 ranged from 0.07 to 5.0 mg/litre during first four weeks. Thereafter the matrix started eroding and the ADR ranged from 5 to 11 mg/litre during the remaining 5 wk. The cumulative release of active ingredient showed that > 90 per cent of the active ingredient was released from the matrix. Interpretation & conclusions: The controlled release matrix of DPE-28 was thus found to inhibit the adult emergence (>80%) of Cx. quinquefasciatus for a period of nine weeks. The CRF of DPE-28 may play a useful role in field and may be recommended for mosquito control programme after evaluating the same under field conditions.

Efficacy of pirimiphos-methyl (50% EC), as a larvicide for the control of Culex quinquefasciatus.

Background & objectives: Pirimiphos-methyl, an organophosphorus insecticide is known to overcome resistance mechanisms of mosquitoes to other organophosphates. Information on the duration of efficacy of pirimiphos-methyl (50% emulsifiable concentrate) for the control of immatures of Culex quinquefasciatus, the vector of bancroftian filariasis, is scanty and hence site specific field trials are necessary to determine the field dosage. Pirimiphos-methyl (50% EC) was tested for its efficacy in cesspits and drains against the immatures of Cx. quinquefasciatus at Puducherry, an endemic area for filariasis, south India. Methods: In cesspits, Pirimiphos-methyl (50% EC) was tested at the dosage of 25, 50, 100 and 200 g(ai)/ ha and in drains at 50, 100 and 200 g(ai)/ha. Immature density during pre-treatment and post-treatment periods was recorded and the efficacy was determined by calculating percentage reduction in larval and pupal densities for a period of about one month. Results: In cesspits, application of the insecticide at 25 and 50 g(ai)/ha reduced the density of larvae by >80 per cent for 2-4 days only, whereas at 100 and 200 g(ai)/ha, the efficacy lasted for 7-8 days. More than 80 per cent reduction was observed in pupal density for 4 days at 50 g(ai)/ha and for 10-12 days at 100 and 200 g(ai)/ha respectively. In drains treated with 50 g (ai)/ha, >80 per cent reduction in larval density was recorded up to 3rd day post-treatment. The efficacy showing >80 per cent reduction in larval density lasted for 12-13 days and the same in pupal density lasted for 10-12 days at 100 and 200 g(ai)/ha. Interpretation & conclusions: At the dosages of 100 and 200 g(ai)/ha, pirimiphos-methyl (50% EC) showed no difference in the control of larvae of Cx. quinquefasciatus in cesspits and drains. Pirimiphosmethyl may be applied at the field dosage of 100 g (ai)/ha at 10 day-intervals in the larval habitats of Cx. quinquefasciatus to achieve >80 per cent reduction in immature density.

Larvicidal & emergence inhibitory activities of NeemAzal T/S 1.2 per cent EC against vectors of malaria, filariasis & dengue.

Background & objectives: Vector control, using agents of chemical origin, continues to be practiced in the control of vector borne diseases. However, due to some drawbacks including lack of selectivity, environmental contamination, and emergence and spread of vector resistance, development of natural products for vector control has been a priority in this area. In the present study we evaluated the larvicidal and emergence inhibitory activities of a neem based formulation Neem Azal T/S 1.2 per cent EC against the vectors of malaria, filariasis and dengue. Method: Larvicidal and emergence inhibition (EI) activity of a neem formulation, NeemAzal T/S 1.2 per cent EC, was studied in the laboratory respectively against early 4th and early 3rd instar larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti following standard procedures. Results: Among the three vector species studied, An. stephensi was highly susceptible to NeemAzal T/S as revealed by the LC50 and LC90 values (1.92 and 2.76 ppm). The formulation produced an overall mortality or inhibition of emergence of 90 per cent (EI90, when 3rd instar larvae were treated) at 0.046, 0.208 and 0.866 ppm in An. stephensi, Cx. quinquefasciatus and Ae. aegypti, respectively. The corresponding EI50 values were 0.006, 0.048 and 0.249 ppm. On treatment, NeemAzal T/S induced certain morphogenetic abnormalities, broadly characterized in five types, in larvae, pupae and adults of all the three vector species. The percentage of dead specimens of any stage showing morphogenetic abnormalities was the maximum in Cx. quinquefasciatus (14.4%; n=2113) followed by Ae. aegypti. Interpretation & conclusions: Our results indicated that because of its emergence inhibition activity, NeemAzal T/S 1.2 per cent EC could be a promising candidate for the use in integrated vector management programme and replace chemical insecticides.

Development of physiological resistance and its stage specificity in Culex quinquefasciatus after selection with deltamethrin in Assam, India

The study investigated the development and stage specificity of physiological resistance to insecticides in a colony of Culex quinquefasciatus Say (Diptera: Culicidae) mosquitoes, which are vectors of bancroftian filariasis in India, after selection with deltamethrin. Resistance was selected by exposing the larvae to the concentration of deltamethrin that caused 50 percent mortality in the tested population (i.e., LC50). Under continuous selection pressure, the LC50 increased steadily in subsequent generations. The estimated LC50 for the F0 generation was 0.409 μg/L; the LC50 first displayed a substantial increase in the F5 generation (5.616 μg/L) and reached 121.902 μg/L in the F10 generation. The objective of this study was to establish a deltamethrin-resistant colony to develop a research programme that will study the evolution of physiological resistance patterns and stage-specific resistance responses in Cx. quinquefasciatus larvae and adults under laboratory conditions. An approximately 298-fold increase in resistance was recorded after 10 generations, as evidenced by the resistance ratio (RR50). The progress and effect of the selection pressure in the adult stage was monitored with the World Health Organisation (WHO) diagnostic test. The mortality, as observed using the WHO diagnostic test, declined significantly from the F5 generation (85 percent) onwards and the highest rate of survival (65 percent) was observed in the F10 generation.

Evaluation of Bacillus sphaericus bioinsecticide produced with white soybean meal as culture medium for the control of Culex (Culex) quinquefasciatus / Avaliação do bioinseticida de Bacillus sphaericus, produzido com meio de cultivo de farelo branco de soja no controle de Culex (Culex) quinquefasciatus

Bioinsecticides are shown to be useful in control programs to prevent several diseases, based on their specificity and efficiency against insect vectors. In the current study a bioinsecticide based on Bacillus sphaericus was produced using a white soybean culture medium and applied to larvae of Culex quinquefasciatus, the susceptible species, and Aedes aegypti, the refractory species used as the negative control. Efficacy was compared with that of the product fermented with the Luria Bertani (LB) reference medium. The experiments showed that C. quinquefasciatus was highly susceptible to the product prepared with white soybean meal, reaching 100 percent larval mortality even at 10mg/L, while A. aegypti failed to reach 70 percent mortality at a concentration of 1g/L. By comparison with the reference medium, the proposed culture medium showed high larvicidal power, reaching a LD90 of 2.26mg/L, while 4.37mg/L was needed for the LB medium to achieve the same mortality rate. Cost comparison between the formulations favored the use of the bioinsecticide produced with white soybean meal. After factoring in the LD90 value, the cost ratio favored the new raw material by nearly 1:220.

A utilização de bioinseticidas tem se mostrado útil aos programas de prevenção de diversas enfermidades devido a sua especificidade e eficiência contra insetos vetores. No presente trabalho, o bioinseticida de Bacillus sphaericus foi produzido com um meio de cultivo composto de farelo branco de soja e aplicado em larvas de Culex quinquefasciatus, espécie susce-tível, e Aedes aegypti, espécie refratária, usada como controle negativo. O desempenho foi comparado com o do produto fermentado com o meio referência Luria Bertani (LB). Os experimentos constataram que C. quinquefasciatus apresentou uma alta suscetibilidade ao produto produzido com farelo branco de soja, alcançando mortalidade de 100 por cento mesmo na diluição de 10mg/L, enquanto A. aegypti não atingiu 70 por cento na concentração de 1g/L. Quando comparado com o meio referência, a formulação proposta proporcionou um alto poder larvicida, alcançando uma DL90 de 2,26mg/L, ao passo que LB precisou de 4,37mg/L para a mesma mortalidade. A comparação do custo das formulações favoreceu o bioinseticida produzido com o meio farelo branco de soja. Considerando os valores de DL90, a relação do custo das matérias-primas ficou próxima de 1:220.

Larval susceptibility of Aloe barbadensis and Cannabis sativa against Culex quinquefasciatus, the filariasis vector.

Larvicidal potential of petroleum ether, carbon tetrachloride and methanol extracts of Aloe barbadensis and Cannabis sativa has been investigated against Culex quinquefasciatus. Among the extracts examined, Carbon tetrachloride extract (Cte) of Aloe barbadensis was the most effective with LC50 values of 15.31 and 11.01 ppm after 24 and 48 hr of exposure, respectively followed by pertoleum ether extract (Pee) of A barbadensis, Cte of C. sativa, methanol extract (Mee) of A. barbadensis, methanol and petroleum ether of C. saliva, LC, being 25.97, 88.51, 144.44, 160.78 and 294.42 ppm affer 24hr and 16.60, 68.69, 108.38, 71.71 and 73.32 ppm after 48 hr of post treatment, respectively. Cte of both the plants exhibits potential larvicidal activity and can be used as ecofriendly alternative in the management of the filariasis vector, Culex quinquefasciatus.

Efficacy of 4-methyl-7-hydroxy coumarin derivatives against vectors Aedes aegypti and Culex quinquefasciatus.

4-Methyl-7-hydroxy coumarin is considered as a lead molecule as a biopesticide. Its mono bromo and tribromo derivatives were synthesized. Two more derivatives were synthesized by acylation. Compound 1 (3,6,8-tribromo-7-hydroxy-4-methyl-chromen-2-one) was found to be the most potent against IVth instar larvae of C. quinquefasciatus and A. aegypti the LC50 being 1.49 and 2.23 ppm respectively. It showed 100% larval mortality at 25 ppm against A. aegypti and at 10 ppm against C. quinquefasciatus. Compounds 1 and 2 (3,6,8-tribromo-7-hydroxy-4-methyl-chromen-2'-oxo-2H-chromen-7-yl acetate) showed remarkable ovicidal activity. Significant reduction of 80-85% hatching of eggs of both mosquito species was observed at the highest dose of 100 ppm. The hatched larvae showed 100% mortality in the successive instars. Compounds 3 and 4 (3-bromo-7-hydroxy-4-methyl-chromen-2-one and 3-bromo-4-methyl-2'-oxo-2H-chromen-7-yl acetate) showed moderate activity against both mosquito species.

Efficacy of agnique (mmf) monomolecular surface film against immature stages of Anopheles arabiensis patton and Culex spp (diptera: culicidae) in Khartoum, Sudan.

The efficacy of the larvicidal and pupicidal agent (Agnique) MMF was evaluated against larvae of An. arabiensis and Culex (Diptera: Culicidae) under field conditions in Bahary Locality, Khartoum, Sudan. At an applied dosage of 0.25 ml/m2, MMF resulted in 89.4, 79.8 and 88.2% reductions in L3-L4 instars An. arabiensis and 63.5% in Culex larvae (all stages) 24 to 72 hours post-treatment. Pupae were completely eliminated (100%) within 24 hours posttreatment. The earlier instars (L1-L2) of An. arabiensis were more tolerant with a 62.5% reduction at 72 hours post-treatment compared to (L3-L4) instars and pupae. At 7-days post-treatment Agnique gave a 57.5% reduction in L1-L2 and 92.6% in L3-L4 instar larvae of An. arabiensis and 57.3% and 86.4% in Culex larvae and pupae, respectively. We conclude that Agnique can perform effectively against L3-L4 instars and pupae of An. arabiensis for only 1 week, and 3 to 4 days against L1-L2 instars of Culex spp.

Use of expanded polystyrene [EPS] and shredded waste polystyrene [SWAP] beads for control of mosquitoes

Mosquitoes transmit several diseases to human. There are several measures for control of larvae. As part of Integrated Vector Management [IVM] program, the utility of floating layers of polystyrene beads [EPS] is a potential alternative in habitats of mosquito larva. EPS beads prevent oviposition of mosquito as well as killing the immature stages by forming a tick layer on the water surface. They are cheap, environmentally safe and do not need frequent application and remain on the surface of water for long time. The objective of the current study was to asses the effectiveness of two types of polystyrene beads of [EPS] and [SWAP] for control of mosquito larvae under laboratory conditions. Anopheles stephensi and Culex quinquefasciatus were used for experimental purposes. In each tray 250 larvae of late 3rd and early 4th instars were introduced. The experiment was conducted on 4 replicates for An. stephensi, Cu. quinquefasciatus and combination of both. Emerging of adult mosquitoes were calculated every day until the end of experiments. Mortality rate and Inhibition of Emerge [IE] for Cu. quinquefasciatus, An. stephensi and combination of both species was 97.8%, 100% and 99.07%, respectively using EPS. In average, EPS was able to kill 98.9% of larvae. The figures with SWAP were 63%, 91.05% and 72.65%, respectively. The average mortality for mosquitoes was 75.57% EPS and SWAP beads can be very effective and practical for elimination of An. stephensi and Cx. quinquefasciatus under the laboratory conditions