Abstract
Mosquito resistance to chemical insecticides and their persistence in the environment promoted the research on natural plant extracts to determine their potential as alternative tools for mosquito control. A study carried out by our team showed that the essential oil of L. alba harvested in Abidjan had insecticidal effect against mosquito vectors. As the biological activity of an essential oil may vary according to its chemotype, the aim of this study was to determine the phytochemical composition of essential oils of L. alba harvested in Bobo-Dioulasso (LA-BF) and Abidjan (LA-CI) and their insecticidal activity on adults of susceptible and resistant strains of Anopheles gambiae (KIS, KdrKIS, Tiass) and Aedes aegypti (SBE, KdrSBE and Abdj). The essential oils were obtained by distillation of the dry leaves using an alembic and a clevenger. Data on the chemical composition of the oils were obtained by GC- MS and analysed using MzMine 2.53 software. The insecticidal effect of the oils was assessed at 0.1 and 1% using the method of WHO test tubes. The main compounds in LA-BF were methyl geranate (16.9%), hepten-2-one (6-methyl-5-) (11.4%), geranial (11.3%) and lavandulyl acetate (9.1%). Those of LA-CI were methyl geranate (14.8%), geranial (9.9%), hepten-2-one (6-methyl-5-) (8.4%) and ocimene (e-beta-) (7.8%). The mortality rates produced by both 0.1% oils on all strains were lower than the 14% achieved by LA-BF on KIS. At 1%, LA-BF and LA-CI induced 100% and 84.9% mortality for KIS, 89.8% and 98.1% for KdrKIS, and 85% and 29% for Tiass, respectively. 100% mortality of SBE strain also observed with LA-CI at 1%. Our study showed that LA-BF and LA-CI were toxic against adults of An. gambiae and Ae. aegypti. Plants have been used for protection against insects since ancient times and remain potential alternatives for the development of natural tools to control mosquitoes.