INSECTICIDAL EFFECT OF SOME BOTANICAL OILS ON LARVAE OF CULEX PIPIENS (DIPTERA: CULICIDAE)

Abstract

Resistance against commonly used insecticides is a serious obstacle against eliminating mosquito-borne diseases. There is a demand for novel safe insecticides to control mosquito populations. This study aimed to evaluate the larvicidal action of essential oils extracted from Citrus limon, Myristica fragrans, Citrus sinensis, Syzygium aromaticum, Carumcarvi, Prunusdulcis, Eucalyptus staigeriana, Rosmarinu sofficinalis, Jasminum officinale, and fixed oil extracted from Linum usitatissimum against Culex pipiens 3rd instar larvae. The LC50 value of lemon oil was the lowest and consequently it has been used for subsequent experiments. Lemon oil was characterised using gas chromatography/mass spectrometry (GC/MS), revealing 36 compounds. Treatment with sublethal lemon oil doses significantly reduced fecundity and fertility of the 3rd instar larvae. Transmission electron microscopy revealed histopathological changes in integument layers of lemon oil-treated larvae. The titre of octopamine was increased in 3rd instar larvae. Additionally, lemon oil demonstrated low cytotoxic effects in WI-38 human cells as evaluated. Given the relative non-lethality of lemon oil to non-targets, it is proposed as a promising and environmentally safe alternative to synthetic insecticides for controlling mosquito populations.