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Bioactivity of
Acyranthes aspera
(Amaranthaceae) Foliage against the Japanese Encephalitis Vector
Culex vishnui
Group
92
Figure 2 Graphical presentation of LC
90
values of crude extract
of
A. aspera
foliage against
Cx. vishnui
group
was correlated with the concentration of exposure (X)
positively with regression coefficient (R
2
) close to 1 in
each case (Table 4). However the non-target
populations were nonresponsive i.e., no changes in the
survival rate and swimming activity, when exposed to
47.30 ppm concentration of acetone extract i.e., LC
50
value of 3
rd
instars for a period of 24 hours. The
larvicidal activity of
A. aspera
leaves were found
statistically significant (p < 0.05) through completely
randomized ANOVA analyses (Table 5).
2 Discussion
Employment of eco-friendly and biodegradable natural
insecticides of plant origin has been recognized and
Table 2 Percent mortality of 3
rd
instars larvae
of Cx. vishnui
group using all the six solvents at 72 hours of post-exposure
Percent mortality ( Mean ± SE) at 72 Hours
Solvent extracts
20 ppm
40 ppm
60 ppm
80 ppm
100 ppm
Petroleum ether
0.00 ± 0.00
0.00 ± 0.00
0.00 ± 0.00
1.00 ± 0.00
1.00 ± 0.00
n-hexane
0.00 ± 0.00
1.2 ± 0.00
0.00 ± 0.00
0.85 ± 0.00
0.00 ± 0.00
Ethyl acetate
4.00 ± 0.72
4.00 ± 1.28
4.00 ± 0.75
4.00 ± 0.72
6.05 ± 0.25
Chloroform: methanol (1:1 v/v)
6.12 ± 0.28
6.12 ± 0.44
7.45 ± 0.88
7.45 ± 1.28
7.45 ± 0.45
acetone
35.00 ± 0.94
47.32 ± 0.82
68.00 ± 0.75
78.00 ± 0.00
95.32 ± 0.82
Absolute alcohol
0.00 ± 0.00
10.00 ± 0.94
16.68 ± 0.94
18.32±0.94
22.00± 0.82
given importance, recently, for mosquito borne disease
control. Larval control is regarded as the best
approach to diminish mosquito population at very
early stage as imprisonment to water bodies and very
stumpy rate of scattering make the mosquito larvae
most susceptible. Hence, mosquito control is mostly
aimed at wrigglers’ control and only against matures
when necessary. Botanicals are proved to be efficient
bio-pesticides not only as crude extract but as solvent
extracts also. Diverse plant ingredients are verified to
be larvicidal (Bhattacharya and Chandra 2013, Kundu
et al., 2013), pupicidal (Rawani et al., 2012),
adulticidal, repellent and smoke toxic (Chowdhury et
al., 2007) against different mosquito species. The
current study well documented the bio-activity of
crude extract of
A. aspera
foliage against
Cx. vishnui
group. Adhikari et al. (2012) established the larvicidal
activity of crude extract of
Swietenia mahagoni
leaves
against
Cx. vishnui
where cent percent mortality of 3
rd
instars was recorded at 0.4% concentration following
an exposure period of 72 h with LC
50
and LC
90
values
of 0.05% and 0.28% correspondingly. However, in the
present study 78.68% mortality of 3
rd
instars was
achieved followed by 72 hours of post exposure at
0.5% concentration with significant (p < 0.05)
elevated values of LC
50
(Figure 1) and LC
90
( Figure 2).
Among all the active fractions the acetone extract of
A.
aspera
showed highest mortality at 100 ppm doses at
72 hour against
Cx. vishnui
group. Singha et al. (2012)
also established the larvicidal effect of acetone extracts
of
Holoptelea integrifolia
against
Cx. vishnui
group
where cent percent mortality was achieved at 400 ppm
concentrations. The larvicidal effect of the present
Journal of Mosquito Research