Preliminary screening of plant essential oils against larvae of Culex quinquefasciatus Say (Diptera: Culicidae)
Preliminary screenings of 22 plant essential oils were tested for mortality of the mosquito larvae Culex quinquefasciatus under laboratory conditions. Percent (%) mortality of the mosquito larvae were obtained for each essential oil. At different exposure periods, viz. 1, 3, 6, 12 and 24 h among the 22 plant oils tested, eight oils viz., aniseed, calamus, cinnamon, clove, lemon, orange, thyme, and tulsi oils gave promising results on larvicidal activity. For larvicidal screening bioassay, the mortality was recorded at different exposure periods viz., 1, 3, 6, 12 and 24 h, and it was found that larval mortality increased when exposure time increased. The clove oil was found to be the most effective treatment. In the preliminary screening, clove oil gave 100% mortality at all exposure periods. Vetiver oil recorded 36.2, 61.2, 76.2, 87.5 and 100% mortality in 1, 3, 6, 12 and 24 h, respectively. Results of this study show that the essential oils may be a potent source of natural larvicides.
Key words: Screening, essential oils, Culex quinquefasciatus, Larvicidal.