Kawal Nyamuk Cara Selamat & Sihat
Racun Serangga Selamat & Sihat
Evaluation of Melaleuca cajuputi (Family:
Myrtaceae) Essential Oil in Aerosol Spray Cans against Dengue Vectors in Low
Cost Housing Flats
2012 Jun 30
Background
Melaleuca cajuputi essential oil in aerosol spray was
evaluated against the dengue vectors Aedes aegypti and Ae. albopictus at low cost housing flats in Section 10, Setapak,
Kuala Lumpur, Malaysia.
Methods:
Essential oil in aerosol viz:
5% and 10% of concentrations were sprayed for 5 seconds each towards hung
mosquitoes in 5 cylindrical net cages. Aerosol weights were recorded before and
after spraying to determine discharge rates. Knockdown and mortality number
were observed and compared to MS standard aerosol which contain 0.07%
prallethrin and 0.05% d-phenothrin as positive control and aerosol contain 40%
kerosene and 60% LPG was used as negative control.
Results:
High knockdown and mortality
was observed in both species of mosquitoes towards MS standard aerosol. There
was a significant difference (P< 0.05)
of mortality and knockdown between 5% and 10% of essential oil aerosol and 5%
and 10% essential oil between MS standard. For 5% essential oil, mean
percentage (%) of knockdown and mortality of Ae. aegypti displayed slightly higher compared to Ae. albopictus. Spraying with 5% M. cajuputi essential oil aerosol indicated a knockdown of Ae. aegypti 5.60±1.18 and mortality of 22.90±4.22 while Ae. albopictus showed 4.60±0.89 knockdown and 20.00±2.85 mortality.
The 10% essential oil concentration gave 23.60±1.68 knockdown and 48.05±0.37
mortality for Ae.
aegypti. Ae. albopictus gave
23.00±3.16 knockdown and 44.20 ± 2.10 mortality respectively.
Conclusions:
Extracts of essential oils
does possessed an adulticidal effects and could
be considered and utilized for future dengue vectors control.
Keywords: Melaleuca cajuputi, essentials
oil, aerosol can, Aedes aegypti, Aedes albopictus
Discussion
In context of pollution
environment such as residue problem, health
risks of the consumer and the development of insect resistance to synthetic insecticides, recent interest among
researchers has developed to investigate and explore potential of plants
extract that are environmentally safe
and target specific but still effective to control vector populations.
From the study, it was observed that
aerosol of MS standard were the most effective followed by essential oil of 10% and 5% concentration respectively.
Pearson’s correlation analysis showed that
the discharge rates had no correlation on the effectiveness (knockdown and
mortality) of the aerosols.
Of all MS standard gave highest mean
percentage of knockdown and mortality of Ae. aegypti and Ae. albopictus compared to the essential oils extract. The mean mortality
percentage for negative control was not more than 20% thus can be said that new
formulations of essential oil have contributed the knockdown and mortality
effect.
Previous studies by Azlinda (2009) on the evaluation of M. cajuputi extract essential oil in aerosol sprays against dengue
vectors in laboratory had similar findings.
That study demonstrated high value of mean
percentage of knockdown and mortality at concentration of 10% with highest
value recorded for knockdown were 37.5±1.33% and mortality were 64.0±5.72%.
In comparison with the present study in
the field trial, the highest number has shown slightly lower of knockdown
(23.60±1.68) and mortality (48.05± 0.37). In spite of that, it indicates the
potential of M. cajuputi essential oil extract as botanical
insecticides in the laboratory as well as in the field.
The bio-efficacy of the products however
depends on many factors such as mode of application and local conditions like
temperature and humidity (Tawatsin et al. 2001).
Study on the evaluation of effectiveness
for household insecticide products performances knockdown time (KT) values is
one of the parameters which contributes not less important.
The knockdown effect were calculated to
estimate the number of knocked down mosquitoes in tested population, as
recommended by WHO (1975) for testing space spraying insecticides such as aerosol.
Values of KT50 and KT95 were lower when
aerosols take shorter time to give knockdown effect. MS standard aerosols give
the lowest values of KT50 and KT95 compared to
the essential oil extracts. However, essential oil with 10% concentration
performs better than 5% concentration.
Similar ported on a study with Callosobruchus maculates of which the knockdown effect varied
with concentrations (Keita et al. 2000). Variation in knockdown time and
mortality were also observed between Ae. aegypti and Ae. albopictus. This probably due to the different reaction to chemical
compound in active ingredients of essential oil which act as a reversible
inhibitor of a acetyl cholinesterase, capable of disrupting the function of
neurotransmitter in insects like mosquito, thus caused knockdown effect (Ryan and Byrne 1988). Recent investigations indicate that
some chemical constituents of many plants extracted essential oils interfere
with the octopaminergic nervous system
in insects. Hence, meet the criteria for
‘reduced risk’ pesticides, as this target site is not shared with mammals (Koul et al. 2008).
From the knockdown and mortality
values, Ae. aegypti showed to be more susceptible
than Ae.
albopictus which
means greater number of knockdown and mortality were noted. Since Ae. aegypti plays a very important role in dengue and dengue
haemorrhagic fever transmission in Southeast Asia and tropical regions (Harinasuta 1984) this
study could provide a useful information in future research.
In conclusion, this study
confirmed that extract of M. cajuputi (Family:
Myrtaceae) essential oil possesses some
adulticidal effects on dengue vectors with most effective concentration was 10%
for controlling vectors.
Similarly, study on the
efficacy of essential oil extract as green
pesticides, has observed that essential oil may require greater application
or frequent reapplication compared to synthetic pesticides (Koul et al. 2008).
Thus, in addition of
development for commercial application of plant essential oil based pesticides,
considerations to include are availability of sufficient quantities of plant
resources, standardization and refinement of pesticide products and regulatory
approval (Isman 2005).The results obtained suggest that,
further studies are considerable essential that will lead to improve
formulations with enhanced activity which may eventually acceptable as mosquito
control.
Acknowledgments
We wish
to thank the Homesafe Products (M) Sdn Bhd in helping and developing essential
oil extract of M. cajuputi plant
into aerosol cans. We appreciate the support of the technical staff from the
Department of Biomedical Science, Faculty of Allied Health Sciences, University
Kebangsaan Malaysia. The cooperation from the resident of low cost housing at
Setapak, Kuala Lumpur and the research grant IRPA 06-02-02-0030EA098 awarded by
Ministry of Science Technology and Innovation Malaysia. The authors declare
that they have no conflicts of interest.
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