Vol. 1, Issue 3, Part A (2014)

Author(s): M. Ramar, S. Ignacimuthu and M. Gabriel Paulraj

Abstract: Essential oils from 12 medicinal plants were evaluated by three different bioassay methods (Vaporizer, Filter paper and Aerosol) for Knock-down and adulticidal efficacy on the filarial vector mosquito, Culex quinquefasciatus. Based on screening results the effective plants were selected for investigating Knock-down and adulticidal potential against adult female of the laboratory-reared mosquito species, Cx. quinquefasciatus. In vaporizer bioassay method four different doses (1.25, 2.5, 5 and 10%) were used. Four different doses (0.625, 1.25, 2.5 and 10%) were used both filter paper (cm²) and aerosol (cm³) bioassay methods. Five essential oils (calamus, camphor, citronella, clove and eucalyptus) were identified as potential treatments in vaporizer bioassay. The result showed that the knock down time decreased with increased concentration in clove oil treatment; the Knock-down time (KT _{50 =} 46.1 ± 0.1, 38.5 ± 0.1, 30.7 ± 0.2, and 20.1 ± 0.1 minutes) was recorded at 1.25, 2.5, 5 and 10% /cm³ respectively. In filter paper method nine essential oils were identified as potential treatments. After 1 hr exposure period clove oil recorded the lowest median Knock-down time (KT₅₀) which was calculated as 9.15 ± 0.1min/cm². Followed by citronella (KT₅₀ =11.4 ± 0.1 min) and eucalyptus (KT₅₀ =11.4 ±0.1min) oils since they recorded lower median Knock-down time. All the twelve essential oils were identified as potential treatments in aerosol activity. The lethal time decreased when the concentration increased. At 5 % concentration the median lethal time (LT₅₀) for clove oil was calculated as (LT₅₀₌3.80 ± 0.1minutes). The Cinnamon oil was effective which recorded (LT₅₀ = 1.99 mins) as median lethal time. Camphor (LT₅₀ =19.6± 0.1 min) oil were found to be less toxic by aerosol method. These results suggest that clove oil and cinnamon oil have the potential to be used as a eco-friendly approach for the control of the major important filaria vector Cx. quinquefasciatus under laboratory condition.