Objective: To assess the repellency to female Aedes aegypti (Ae. aegypti), Anopheles dirus (An. dirus) and Culex quinquefasciatus (Cx. quinquefasciatus) of seven essential oils using two treatment methods. Methods: Topical applications of three dose concentrations (0.02, 0.10 and 0.21 mg/cm2) were made on the forearms of volunteers. Dose-response study and protection time study were employed in the experiment. Results: In the dose-response test, Cymbopogon citratus (C. citratus), Cymbopogon nardus (C. nardus), Syzygium aromaticum (S. aromaticum) and Ocimum basilicum (O. basilicum) exhibited a high repellency against Ae. aegypti with ED50 at < 0.045 mg/cm2, whereas C. citratus, C. nardus and S. aromaticum showed repellency against An. dirus with ED50 at <0.068 mg/cm2. Furthermore, the essential oils of C. citratus, C. nardus, S. aromaticum, O.basilicum and Cananga odorata gave strong effective dose (ED 50) values at <0.003 mg/cm2 when tested against Cx. quinquefasciatus. For testing by arm in cage method, at 0.21 mg/cm2, protection time of C. citratus gave the longest lasting period against three mosquito species, 72 min for Ae. aegypti, 132 min for An. dirus and 84 min for Cx. quinquefasciatus. In addition, the two essential oils exhibited moderate repellency against Ae. aegypti, An. dirus and Cx. quinquefasciatus, at 60, 90 and 78 min with C. nardus, and 54, 96 and 72 min with S. aromaticum, respectively. Conclusions: The percentage repellency increased when the concentration of essential oils increased. In contrast, biting rates decreased when the concentration of essential oils increased.C. citratus exhibited high efficiency for the protection time and the percentage of biting deterrent against all of 3 mosquito species.

Abstract. The effect of oviposition-deterrent and ovicidal of seven essential oils were evaluated towards three mosquito vectors, Aedes aegypti, Anopheles dirus and Culex quinquefasciatus. The oviposition activity index (OAI) values of six essential oils namely Cananga odorata, Cymbopogon citratus, Cymbopogon nardus, Eucalyptus citriodora, Ocimum basilicum and Syzygium aromaticum indicated that there were more deterrent than the control whereas Citrus sinensis oil acted as oviposition attractant. At higher concentration (10%) of Ca. odorata (ylang ylang flowers) showed high percent effective repellency (ER) against oviposition at 99.4% to Ae. aegypti, 97.1% to An. dirus and 100% to Cx. quinquefasciatus, respectively. The results showed that mean numbers of eggs were lower in treated than in untreated water. In addition, there was an inverse relationship between essential oil concentrations and ovicidal activity. As the concentration of essential oil increased from 1%, 5% and up to 10% conc., the hatching rate decreased. The essential oil of Ca. odorata at 10% conc. gave minimum egg hatch of 10.4% (for Ae. aegypti), 0.8% (for An. dirus) and 1.1% (for Cx. quinquefasciatus) respectively. These results clearly revealed that the essential oil of Ca. odorata served as a potential oviposition-deterrent and ovicidal activity against Ae. aegypti, An. dirus and Cx. quinquefasciatus.

Objective:To evaluate adulticidal,larvicidal and oviposition deterrent response of the essential oil from dried Zanthoxylum limonella (Z.limonella) fruit against Aedes aegypti (Ae.aegypti) and Culex quinquefasciatus (Cx.quinquefasciatus).Methods:Z.limonella oil was tested by biological assays at 1％,5％ and 10％ concentrations in ethanol.Adulticidal efficacy was tested against the 2-3 day old adult females.Larvicidal activity was tested against immature stage of mosquitoes.Oviposition deterrence of the oil was evaluated on gravid females.Results:The adult mortality was observed after 24 h with the LC5o of 6.0％ for Ae.aegypti,and 5.7％ for Cx.quinquefasciatus.Larvicidal bioassay was carried out with the 10％ Z.limonella oil against immature stages of Ae.aegypti and Cx.quinquefasciatus,which caused 100％ mortality after 12 h and 24 h.In the larvicidal experiment,Z.limonella showed effective result at 1％,5％ and 10％ concentrations with the values of LT5o Ae.aegypti =9.78,5.61,0.24 h for larvae and LT5o =64.08,21.23 h for pupae;Cx.quinquefasciatus had LT50 =28.46,20.25,1.01 h for larvae and LT50 =67.52,27.96,4.11 h for pupae,respectively.Oviposition deterrence of the oil was evaluated on gravid females.In the study,10％ Z.limonella showed 100％ repellency for Ae.aegypti and 99.53％ for Cx.quinquefasciatus.Likewise,oviposition activity indexes of these oil concentrations were all negative values ranging from-0.89 to-1.00 for Ae.aegypti and-0.64 to-0.99 for Cx.quinquefasciatus.The oviposition activity indexes values revealed that Z.limonella oil has deterrent effect,and it caused a remarkable negative response resulting in very few eggs.Conclusions:This result indicates that Z.limonella oil can be used as an effective adulticide,larvicide and oviposition deterrent against Ae.aegypti and Cx.quinquefasciatus.

Objective To evaluate adulticidal, larvicidal and oviposition deterrent response of the essential oil from dried Zanthoxylum limonella (Z. limonella) fruit against Aedes aegypti (Ae. aegypti) and Culex quinquefasciatus (Cx. quinquefasciatus). Methods Z. limonella oil was tested by biological assays at 1%, 5% and 10% concentrations in ethanol. Adulticidal efficacy was tested against the 2–3 day old adult females. Larvicidal activity was tested against immature stage of mosquitoes. Oviposition deterrence of the oil was evaluated on gravid females. Results The adult mortality was observed after 24 h with the LC