Impact ofCymbopogon flexuosus(Poaceae) essential oil and primary components on the eclosion and larval development ofAedes aegypti(Diptera: Culicidae)

AbstractThe current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) ofCymbopogon flexuosusessential oil (EO) on the development ofAedes aegypti(L.) eggs and larvae. To demonstrate the ovicidal activity of EO, we treated embryonated eggs with 6, 18, and 30 mg.L-1and larvae with 3 and 6 mg.L-1EO concentrations. Citral and geranyl acetate were evaluated at 18, 30, and 42 mg.L-1and compared with commercial growth inhibitors (diflubenzuron and methoprene) at 3 and 6 mg.L-1concentrations. For each treatment, we measured larval head diameter, siphon length, and body length. To complement the morphological analysis, we examined concentrations of moult hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography (HPLC) coupled to mass spectrometry. The EO decreased egg hatching at all concentrations: 6 mg.L-1in 45.3%; 18 mg.L-1in 23.3%, and 30 mg.L-1in 34.6%. EO also altered molting among larval instars and between larvae and pupae, with an increase in the length (3 mg.L-1: 6 ± 0.0 mm; 6 mg.L-1: 6 ± 0.7 mm) and head width (3 mg.L-1: 0.8 ± 0 mm; 6 mg.L-1: 0.8 ± 0.0 mm) compared with the control group (length: 5.3 ± 0 mm; head width: 0.7 ± 0.0 mm). We did not detect chromatographic signals of MH and JH III in larvae treated withC. flexuosusEO or their major compounds. The sub-lethal concentrationsC. flexuosusEO caused a similar effect to diflubenzuron, decreasing hormone concentration, extending the larval period, and death.