Eco-Friendly Control of Culex quinquefasciatus Say (Diptera: Culicidae) through Botanical Insecticides and Predatory Insects

Abstract

The present study aims to evaluate the efficacy of n-hexane extracts of two medicinal plants, Artemisia scoparia and Anisomeles indica against larvae, pupae and adults of Culex quinquefasciatus. The study also evaluated the predatory effects of the diving beetle, Agabus cybister, against various instar larvae of Cx. quinquefasciatus. Bioassay of whole-plant extracts was performed following WHO methods, with slight modifications. LC50 values for A. scoparia and A. indica against early fourth instar larvae were 360.4 and 971.1 ppm, respectively. LC50 values for pupae were 1665 and 2838 ppm for A. scoparia and A. indica extracts, respectively. Percent knockdown after 1 h exposure was 49.0 for A. scoparia. KDT50 and KDT90 values for A. scoparia were 69.7 and 763.5 min, respectively. LC50 values for A. scoparia and A. indica against adult mosquitoes were 0.266 and 3.364 per cent respectively. A linear relationship was found between extract concentration and mosquitocidal activity. Regarding predatory control, it was found that during a 12-hour laboratory study, A. cybister consumed 10 exposed larvae. Under field conditions, introduction of predator decreased the larval density from 141.7 to 71 in 15 days. In conclusion, these plants and predator may be useful in controlling mosquito populations in an eco-friendly way.