Repellency of volatile oils from plants against three mosquito vectors

Volatile oils extracted by water distillation from four plants species, turmeric (Curcuma longa), kaffir lime (Citrus hystrix), citronella grass (Cymbopogon winterianus) and hairy basil (Ocimum americanum), were evaluated under laboratory and semi-field conditions for their repellency against three mosquito vectors, Aedes aegypti, Anopheles dirus and Culex quinquefasciatus. The oils from turmeric, citronella grass and hairy basil, especially with the addition of 5% vanillin, repelled the three mosquito species under laboratory conditions for up to 8.0 hours. The oil from kaffir lime alone as well as with 5% vanillin added was effective for up to 3.0 hours. The standard repellent, deet (N, N-diethyl-3-methylbenzamide), provided protection for at least 8.0 hours against Ae. aegypti and Cx. quinquefasciatus, but for 6.0 hours against An. dirus. However, deet with the addition of 5% vanillin gave protection against the three mosquito species for at least 8.0 hours. The results of semi-field evaluations confirmed the repellency obtained under laboratory conditions. This study demonstrates the potential of volatile oils extracted from turmeric, citronella grass and hairy basil as topical repellents against both day and night-biting mosquitoes. The three volatile oils can be formulated with vanillin as mosquito repellents in various forms to replace deet, the most common repellent chemical currently available