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JOURNAL OF MOSQUITO RESEARCH
98
1997; ICMR, 2000; Tawatsin
et
al
., 2001),
Ocimum
selloi
against
Anopheles braziliensis
(Paula
et al
., 2003)
and neem against
Aedes
,
Culex
,
Anopheles
and
Armigeres
mosquitoes (Sharma
et al
., 1993; Dua
et al
.,
1995; Mishra
et
al
., 1995; Pandian and Devi, 1998).
Interest in anti-mosquito products of plant origin is
being revived because of the drawbacks associated
with the continued application of synthetic
compounds, some of which have led to widespread
development of insecticide resistance. Some people
mainly in rural areas burn plant materials using
glowing charcoal to produce smoke which repels or
kills mosquitoes. Therefore, in the present study,
evaluations were carried out by burning leaves of five
plants
viz., Azadirachta indica, Citrus medica
,
Murraya koenigii, Ocimum tenuifloreum
and
Ricinus
communis
using glowing charcoal for their repellent
activity against mosquitoes.
1 Results
In the present study, the repellent activity of selected
local plants
viz., Azadirachta indica, Citrus medica
,
Murraya koenigii, Ocimum tenuifloreum
and
Ricinus
communis
was evaluated. The results indicated that
amongst the five plants utilized,
Azadirachta
indica
,
Murraya
koenigii
,
Citrus
medica
exhibited more
repellence followed by
Ricinus
communis
and
Ocimum
tenuifloreum
with a range between 25 to 75%
repellent activity (Table 1). Maximum repellence was
provided by
Azadirachta
indica
leaves in house 1 with
a protection time of six hours. In house 2 it was
Azadirachta
indica
and
Murraya
koenigii
and in house
3,
Murraya
koenigii
and
Citrus medica
with six hours,
whereas in house 4 it was
Azadirachta
indica
,
Ricinus
communis
and
Ocimum
tenuifloreum
with four hours
(Figure 1). House 5 which served as negative control
provided forty five minutes protection time and in the
case of house six (positive control) no repellence was
observed. The present study also indicated that the
incidence of mosquito bites significantly reduced after
usage of plant products.
2 Discussion
Mosquitoes are a serious threat to public health
transmitting several dangerous diseases for over two
billion people in the tropics. There has been a large
increase in the insecticide resistance of this vector and
has become a global problem. Insecticides residues in
the environment, as a result of chemical insecticide
usage, have turned the researcher’s attention towards
natural products (Murty and Jamil, 1987). In the past
years, the plant kingdom has been of great interest as a
potential source of insecticidal products. Many species
in the plant kingdom synthesize a variety of secondary
metabolites which play a vital role in defense of plants
against insects/mosquitoes. Plants may be alternative
source for mosquito repellent agents since they
constitute a rich source of bioactive chemicals (Wink,
1993). Plant products can be used, either as an
insecticide for killing larvae or adult mosquitoes or as
repellents for protection against mosquito bites,
depending on the type of activity they posses (ICMR,
2003). Products of secondary plant metabolisms may
be responsible for the chemical communication
between plants and insects. Allelochemicals have been
considered as potential natural insecticides and can be
used for insect/mosquito management in integrated
control (Jilani and Su, 1983). Phytochemicals
obtained from plants are usually less environmentally
harmful than synthetic chemicals and it has renewed
the interest in the research on phytocompounds,
considering them as an ecologically safe alternative
for synthetic insecticides (Isman, 2006). A review of
botanical phytochemicals with mosquitocidal potential
published by Shaalan et al. (2005) demonstrates
identification of novel effective mosquitocidal compounds
from botanicals containing active phytochemicals.
Table 1 Details of plant leaves utilized for the repellent study
Plant name
Scientific name
Vernacular name (Tamil)
Family
Neem
Azadirachta indica
Vembu
Meliaceae
Lemon
Citrus medica
Naarthangaai
Rutaceae
Curry leaf
Murraya koenigii
Karuveppilai
Rutaceae
Holy basil
Ocimum tenuifloreum
Ram/Lakshmi tulsi
Lamiaceae
Castor
Ricinus communis
Amanakku
Euphorbiaceae