Affiliations: * National Institute of Health, Department of Medical Sciences,
Ministry of Public Health, 88/7 Tiwanon Rd., Nonthaburi 11000, Thailand
** Medicinal Plant Research Institute, Department of Medical Sciences, Ministry of Public Health, 88/7 Tiwanon Rd., Nonthaburi 11000, Thailand
Source: Presented in the 3rd International Congress of Vector Ecology, Barcelona,
Spain, 16-21 September 2001
Volatile oils extracted by steam distillation from rhizomes of turmeric (Curcuma longa Linn.) and galangal minor (Alpinia officinarum Hance) were evaluated for ovipositional deterrence, larvicidal and repellent activities against four mosquito vectors: Aedes aegypti (L.), Ae. albopictus (Skuse), Anopheles dirus Peyton & Harrison, and Culex quinquefasciatus Say. In three-choice oviposition assays carried out in cages in the laboratory, open cups in which water was treated with turmeric oil and galanga oil (each with 5 ul of the extracts) received significantly fewer mosquito eggs or egg rafts than did untreated cups. However, the mosquito eggs or egg rafts obtained from the cups treated with turmeric oil were significantly lower than in cups treated with galanga oil. Evaluations of larvicidal activity conducted in laboratory reveled that both oils provided a high degree of larvicidal effects against larvae of the four mosquito species tested. Turmeric oil exhibited LC50 of 53.9, 11.4, 1.2 and 30.6 ppm against the fourth instar larvae of Ae. aegypti, Ae. albopictus, An. dirus and Cx. quinquefasciatus, respectively, whereas those obtained from galanga oil were 77.5, 47.1, 20.5 and 55.7 ppm, respectively. Regarding repellent efficacy against host-seeking mosquitoes tested in cages in laboratory, turmeric oil repelled adults of the four mosquito species for up to 8 hours, whereas galanga oil showed less repellency against the mosquitoes than did turmeric oil. However in the field, turmeric oil provided protection from biting of various mosquito species, such as Ae. albopictus, An. barbirostris, An. umbrosus, Armigeres subalbatus, Cx.gelidus, Cx. quinquefasciatus, Cx. tritaeniorhynchus, Mansonia annulifera, Ma. dives, Ma. indiana, Ma. uniformis during the 12 hours of exposure period, between 1800 h to 0600 h. In conclusion, this study demonstrated the potential uses of volatile oils extracted from turmeric and galanga as natural products for prevention and control of mosquito-borne diseases.