Background: Mosquitoes transmit serious human diseases, causing millions of deaths every year. Use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of botanical origin have been reported as useful for control of mosquitoes. Azadirachta indica (Meliaceae) and its derived products have shown a variety of insecticidal properties. The present paper discusses the larvicidal activity of neem-based biopesticide for the control of mosquitoes.
The repellent properties of different fractions isolated from Lantana camara flowers by using steam distillation, solvent partition and chromatographic methods were evaluated against Aedes mosquitoes. Maximum protection time of one fraction eluted by chloroform from a silica gel column was 3.45 h. One application of this fraction gave 100% protection for 2 h and may protect 75.8% at 7 h (t ¼ 7.00, P < 0.001) against the bites of Aedes mosquitoes. Further purification of the most efficient fraction into pure compounds did not result in any increase in repellency.
The larvicidal activity of roots of Hibiscus abelmoschus was evaluated against the larvae of mosquitoes in the genera Anopheles and Culex. Mean median lethal concentration values of the aqueous extract from the roots of H. abelmoschus against the larvae of Anopheles culicifacies, An. stephensi, and Culex quinquefasciatus were 52.3, 52.6, and 43.8 ppm, respectively. Efficacy of fraction code HAM-4 decreased with an increase in water depth when sprayed at a dose calculated by surface area. Fraction code HAM-4 at the rate of 82 ppm showed 91.1% reduction of larval An. stephensi in a tank, whereas 87.4% reduction of larval Cx. quinquefaisciatus occurred in a blocked drain 24 h after application of HAM-4 under field conditions.
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