Larvicidal and pupicidal efficacy of plant oils against Culex quinquefasciatus Say 1823 (Diptera: Culicidae)
Manickkam Jayakumar, Subramanian Arivoli, Rajasingh Raveen and Samuel Tennyson
Mosquitoes are responsible for the transmission of diseases, such as malaria, filariasis, Japanese encephalitis, dengue, chikungunya, Zika virus disease, etc. causing millions of deaths every year. Repeated use of synthetic insecticides for mosquito control has disrupted the environment. This has necessitated the search for alternative approach for mosquito control programme using natural products of plant origin especially plant oils. Therefore in the present study, the bioactivity of plant oils viz., aniseed, camphor, citronella, eucalyptus, geranium, lavender, lemon, rosemary, vetiver and wintergreen were tested at concentrations of 125, 250, 500 and 1000mg/L against the third instar larvae and pupae of Culex quinquefasciatus in the laboratory. Results revealed varying degree of toxicity by plant oils on the larvae and pupae of Culex quinquefasciatus. Among the plant oils tested, eucalyptus showed the highest activity whose LC50 value was 186.77 and 206.08mg/L against the larvae and pupae of Culex quinquefasciatus followed by vetiver with 470.37 and 239.39mg/L respectively. One hundred per cent larval mortality was recorded in eucalyptus oil at 1000mg/L after 24 hours of exposure. The order of the larvicidal efficacy of plant oils after 24 hours were eucalyptus > vetiver > camphor > lemon > citronella > lavender > aniseed > wintergreen > rosemary > geranium whereas for pupicidal efficacy, it was eucalyptus > vetiver > geranium > lemon > camphor > wintergreen > rosemary > aniseed > citronella > lavender oil.