Chemical Compositions of Crassocephalum crepidioides Essential Oils and Larvicidal Activities Against Aedes aegypti , Aedes albopictus , and Culex quinquefasciatus

The leaf, stem, and floral essential oils of Crassocephalum crepidioides growing wild in central Vietnam were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. The major component in all 3 oils was myrcene (59.3%, 26.1%, and 43.3%, respectively). The 24-hour mosquito larvicidal activities of the oil of the aerial parts (stems and leaves) were determined against wild-caught Aedes albopictus (IC 50 = 14.3 μg/mL), laboratory-reared Aedes aegypti (IC 50 = 4.95 μg/mL), and wild-caught Culex quinquefasciatus (IC 50 = 18.4 μg/mL). The high concentration of myrcene in the essential oil likely accounts for the mosquito larvicidal activity observed.