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Background and Objectives: Insecticide resistance in malaria vectors has been a major challenge to vector control programs and updated information to the commonly used insecticides is essential for planning appropriate vector control measures. Anopheles culicifacies and An. fluviatilis are the two main vectors prevalent in Jharkhand state of India and role of An. minimus is contemplated in the transmission of malaria in this state. All the districts in the state are predominantly inhabited by the tribal population and are endemic for malaria. A study was undertaken in 12 districts of Jharkhand state to determine the insecticide susceptibility status of the 3 prevalent primary vector species, An. culicifacies, An. fluviatilis, and An. minimus., Methods: Wild-caught adult female An. culicifacies, An. fluviatilis, and An. minimus, mosquitoes were collected from stratified ecotypes from different localities of 12 tribal districts of Jharkhand state during 2018 and 2019. Susceptibility tube tests were conducted following the WHO method using test kits. Mosquitoes were exposed to WHO impregnated papers with the prescribed discriminatory dosages of DDT - 4%, malathion - 5%, deltamethrin - 0.05%, permethrin - 0.75%, cyfluthrin - 0.15% and lambda cyhalothrin - 0.05%., Results: Results indicated that An. culicifacies has developed multiple insecticide resistance in all the 12 districts of Jharkhand state. An. fluviatilis was reported resistant for the first time to DDT in all the districts but was susceptible to malathion, deltamethrin, and permethrin whereas in one district it showed possible resistance to malathion. An. minimus was studied in Noamundi CHC of West Singhbhum district, showed possible resistance against DDT but was susceptible to malathion, deltamethrin, and permethrin., Interpretation & Conclusion: The development of multiple insecticide resistance in An. culicifacies including to pyrethroids, has been a concern for malaria control programmes for effective vector management but a report of resistance to DDT for the first time in An. fluviatlis in all the districts in the state is alarming, An. minimus was found in possible resistance category to DDT in one district and both the species were reported susceptible to malathion, deltamethrin, and permethrin. The result of the present study indicates a need for regular monitoring to assess the insecticide susceptibility to formulate effective vector control measures and resistance management., Competing Interests: None

The larvicidal activity of Mentha piperita, Cymbopogan citratus (lemongrass), Eucalyptus globulus and Citrus sinensis (orange) essential oils and their combinations was evaluated against Musca domestica (housefly) and Anopheles stephensi (mosquitoes) through contact toxicity assay. Among all the tested essential oils/combinations, Me. piperita was found to be the most effective larvicidal agent against Mu. domestica and An. stephensi with LC50 values of 0.66 μl/cm(2) and 44.66 ppm, respectively, after 48 h. The results clearly highlighted that the addition of mentha oil to other oils (1:1 ratio) improved their larvicidal activity. The order of effectiveness of essential oils/combinations indicated that the pattern for An. stephensi follows the trend as mentha > mentha + lemongrass > lemongrass > mentha + eucalyptus > eucalyptus > mentha + orange > orange and for Mu. domestica as mentha > mentha + lemongrass > lemongrass > mentha + orange > orange > mentha + eucalyptus > eucalyptus. The images obtained from scanning electron microscopy (SEM) analysis indicated the toxic effect of Me. piperita as the treated larvae were observed to be dehydrated and deformed. This study demonstrates the effectiveness of tested essential oils/combinations against the larval stages of Mu. domestica and An. stephensi and has the potential for development of botanical formulations.

Background & Objectives: Phlebotomus argentipes is the vector for visceral leishmaniasis in India. The development of resistance in kala-azar vector to DDT has been reported from various parts of India. The main objective of this study was to generate information on insecticides susceptibility status of P. argentipes to DDT, malathion and deltamethrin in different parts in three states of India., Methods: Phlebotomus argentipes were collected from different villages, identified and used to investigate the susceptibility status against DDT, malathion and deltamethrin as per the WHO standard methods., Results: Phlebotomus argentipes was resistant to DDT in different areas, viz. PHCs Murumgaon in Maharashtra; Ramgarh in Jharkhand; Kodah, Falka, Mahua and Lalganj in Bihar. In Phulwari Shareef PHC of Patna district in Bihar, DDT produced 89% mortality in P. argentipes, indicating resistant/tolerance (verification required) to DDT. The corrected percent mortality to malathion (5%) in different areas ranged between 98 and 100%; and to deltamethrin (0.05%) between 98.4 and 100%. The results showed that the tested P. argentipes are susceptible to malathion and deltamethrin., Conclusion: Phlebotomus argentipes are still susceptible to malathion and deltamethrin, but resistant to DDT. The susceptibility status of P. argentipes should be monitored regularly in diversified situations to ascertain the judicious use of insecticides being used for indoor residual spraying in the programme for rational use of appropriate insecticide.

Hexane extract obtained from leaves of Eucalyptus citriodora Hook was tested against larvae of Anopheles stephensi Liston, Culex quinquefasciatus Say and Aedes aegypti Linn to assess its toxicity and growth inhibiting activity. The results showed better activity of hexane extract against larvae of An. stephensi Liston as compared to the larvae of Cx. quinquefasciatus Say and Ae. aegypti Linn. The LC50 values against IVth instar larvae of three species were 69.86, 81.12 & 91.76 ppm respectively after 24 hours and 26.7, 29.9 & 38.8 ppm respectively after 72 hours. At lowest concentration viz. 10 ppm, 73% larvae of An. stephensi Liston failed to emergence as adult mosquito while in Cx. quinquefasciatus Say and Ae. aegypti Linn only 10 & 6% larvae failed to emerge. Further observations showed some morphological abnormalities in same pupae which could not moult normally. These results clearly indicated growth inhibition effect of the hexane extract of Eucalyptus against mosquito larvae, particularly Anopheles species. Thus Eucalyptus citriodora Hook, which is commonly found in Northern India, has a great potential for the development of an eco-friendly herbal insecticidal product for control of mosquito breeding.

Fresh leaf extract of milkweed (Calotropis procera) showed larvicidal properties against mosquito larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti. Methanolic extracts of the same plant were, however, more effective as larvicide. C. procera is a weed growing in uncultivated soils as well as in dry, arid zones in Indian subcontinent throughout the year. The results of this study suggest the utility of milkweed as potential technology for control of mosquito larvae.

Background & Objectives: In India, temephos and fenthion are used as larvicides in fresh and polluted waters. Since use of same insecticide may precipitate resistant, as an alternative bioefficacy of pirimiphos-methyl--an organophosphorus insecticide was evaluated against immatures of Anopheles and Culex species in different breeding habitats in District Ghaziabad (U.P.) and Goa., Methods: Laboratory bioassays were carried out using standard WHO procedure. LC50 and LC90 were calculated using Probit analysis. Abbott's formula was used to calculate per cent corrected mortality in laboratory exposures while, Mulla's formula was applied for calculating per cent reduction in mosquito immatures under field conditions., Results: Pirimiphos-methyl was found to be most effective against larvae of An. stephensi followed by An. culicifacies and Cx. quinquefasciatus. The LC50 and LC90 values against three species were 0.023, 0.032 and 0.04 ppm; and 0.045, 0.057 and 0.114 ppm respectively. In field, pirimiphos-methyl @ 200 g a.i./ha against Anopheles species and @ 300 g a.i./ha against Culex species can produce > 80% reduction in density of immatures up to one week in different habitats. Pirimiphos-methyl < 0.25 ppm is not toxic to fish., Interpretation & Conclusion: Pirimiphos-methyl is more effective against anophelines in clean water than culicines in polluted water. This larvicide should not be used at a concentration above 0.25 ppm in habitats harbouring the larvivorous fish.