Oramon Santiwitchaya¹
Luepol Punnakunta¹
Prathuengsri Sinchaisri¹
Usavadee Thavara²

Affilications :
      ¹ Faculty of Environmental and Resource Studies, Mahidol University, Thailand
      ² National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Thailand

Source:
      Presented in the fourth International Conference on Biopesticides Feb 13-18, 2005, Chiang Mai.

Language :
      English

Abstract :

      The volatile oils derived from three plant species, Lemon grass (Cymbopogon citratus ), Citronella grass (Cymbopogon nardus ) and May Chang (Litsea cubeba ) were extracted by hydro-distillation and evaluated for mosquito repellent activity against Aedes aegypti  and Culex quinquefasciatus  under laboratory conditions. The volatile oil yields obtained from fresh parts of Lemon grass (leaves), Citronella grass (leaves) and May Chang (fruits) were 0.64% (v/w), 1.04% (v/w) and 3.66% (v/w), respectively. Each oil was prepared as liquid formulation (non-gassed spray) at three different concentrations: 5%, 10% and 15% in ethanol (95%) and then tested against the mosquitoes in a test room at the dosage of about 0.18 - 0.2 g/m³. Assessments were carried out by comparison of mosquitoes captured by volunteers in the test area (with repellent spraying) and the controlled area (without repellent spraying). Overall, repellencies of the three volatile oils against Cx. quinquefasciatus  were significantly higher than those obtained from Ae. aegypti . The repellencies of Lemon grass, Citronella grass and May Chang against Cx. quinquefasciatus  were 28.2 - 68.2%, 33.3 - 80.7% and 48.1 - 76.2%, respectively; whereas those against Ae. aegypti  were 4.7 - 23.6%, 0 - 32.3% and 20.5 - 28.9%, respectively. There is no significant difference among repellencies obtained from the three volatile oils against Cx. quinquefasciatus  as well as against Ae. aegypti . This study therefore indicated that volatile oils derived from Lemon grass, Citronella grass and May Chang were equally effective as mosquito repellent against Cx. quinquefasciatus  and could be useful for protection from biting of the mosquitoes. However, the volatile oil obtained from May Chang is considered to be the most appropriate source of repellent products according to its nice smell and high yield.