Efficacité de quelques extraits botaniques à l’égard de Culex pipiens L. (Diptera : Culicidae) ; Caractérisation chimique, Toxicité, Biochimie et Reproduction

Abstract

Mosquitoes are the most medically important vector borne disease arthropods. Unfortunately, their resistance to conventional insecticides is a growing global threat that needs to be addressed. Plant-derived pesticides are biodegradable, ecofriendly, and could be an alternative to synthetic pesticides. The present study was designed to explore the insecticidal effect of ethanolic extracts of leaves and flowers of Borago officinalis (Boraginaceae) and Lantana camara(Verbenaceae). Results of the larvicidal activity of different extracts were estimated against newly molted fourth-instar larvae (L4) of CulexpipiensL. (Diptera: Culicidae). According to the calculated lethal concentrations (LC30 and LC50), the ethanolic extract of L. camaraflowers was the most toxic with an LC50 = 1.48% compared to the other extracts. The extracts affected the growth and development of Cx. pipiens. L. camaraand B. officinalis leaf extracts decreased the body weight of the studied instars and significantly prolonged L4 and pupal development durations, and females appeared more sensitive. In addition, whole-body biochemical analyses of the different developmental instars indicated a significant decrease in energy reserve levels (carbohydrates and lipids) and an increase in proteins in females following application of the four extracts. Neurotoxicity (inhibition of specific AChE activity) was revealed in L4 treated with the extracts, with a more pronounced effect with B. officinalis. B. officinalis leaf extract deviated the sex ratio of adults in favor of males. Also, wing length of both sexes and reproductive potential (fertility and fecundity) were significantly decreased in adults from L4 treated with the ethanolic extract of L. camara flowers. The detoxification system (GST induction) was induced during the first 24h with L. camaraand during 48h with B. officinalis. The ethanolic extracts of the leaves of B. officinalisand the flowers of L. camararevealed significant contents of polyphenols, flavonoids and tannins, with a very significant antioxidant activity. On the other hand, the anti-inflammatory activity was identical. The results reveal that the extracts of both tested plants could be used to control mosquito larvae and adults, instead of conventional insecticides. Further studies must be conducted to identify the active components and their mode of action.