final .cdr

9
employing standard WHO procedure . Batches of 25 larvae
were exposed to known concentration of test solution (249
ml dechlorinated tap water and 1ml of DMSO dissolved test
extract) in glass beakers of 500 ml capacity. Three replicate
sets were tested with a final tally of 75 larvae for each
concentration. Solutions containing 249 ml tap water and
1ml of DMSO, without plant sample served as controls. No
food was provided to the larvae during the test period.
Mortality and survival were monitored after 24 h of
treatment. The moribund and dead larvae in replicates were
combined and expressed as percentage mortality. The larvae
were considered as dead or moribund, if they were not
responsive to a gentle prodding with a fine needle.
Experiments were conducted at 25±2 ˚C, 12 h light/dark
regime. The observed percent mortality was adjusted with
10
the control mortality, using Abott's formula and expressed
as corrected mortality. These were subjected to regression
analysis of probit mortality on log dosage using
computerized log-probit analysis, which provided the lethal
dosage of 50, 90, 95 and 99ppm as well as their 95%
11
confidence limit .
Repellency tests
S. Swathi et al Larvicidal and repellent activities of ethanolic extract of pongamia pinnata leaves against mosquitoes
The ethanolic extract of Pongamia pinnata leaves was
evaluated for repellent activities against Aedes aegypti,
Anopheles stephensi and Culex quinquefasciatus using the human –
12
bait technique . The plant extract was diluted in ethanol
and 0.1, 0.5 and 1% concentrations were prepared. For
each test, 10 disease free, laboratory-reared female
mosquitoes were placed into separate laboratory cages
13
(45x38x38 cm) . The mosquito progenies obtained from
laboratory colony were maintained in a cloth cage under
controlled temperature (28±2°C) and relative humidity
14
range (75–80%) . Three volunteers were considered for
performing human-bait technique. Before each test, the
volunteer's skin was washed with unscented soap and the
tested solution was applied from the elbow to the finger tips
13
. The test was repeated at every 30 min interval. The
interval between the application of repellent and the first
two consecutive bites occurring within 30 min was
considered as protection time against the bites afforded by
14
each of the concentrations of the test repellents . In each
cage one arm was inserted for one test concentration and the
other arm applied with ethanol served as control. The
treated and control arms were interchanged regularly to
eliminate bias. Each test concentration was repeated three
times and in each replicate subject different volunteers to
nullify any effect of color of the skin on repellent. Volunteers
13
were asked to follow the testing protocol . The complete
protection time (min) for each concentration was
14
calculated .
RESULTS
Results of the larvicidal and repellent activities of ethanolic
extract of Pongamia pinnata leaves against Aedes aegypti,
Anopheles stephensi and Culex quinquefasciatus are presented in
Table : - 1 and 2. The data was recorded, the LD 50 (50%
lethal dose) , LD 90 (90% lethal dose) , 95 % Confidence limit
and Chi – square value were calculated.
Table1: Larvicidal efficacy of Pongamia pinnata leaves against Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus.
S.No Mosquito species LD (50% LD (90% 95 % (Confidence Chi – square
50
2
lethal dose) lethal dose) limit) value(x )
(ppm) (ppm)
1. Aedes aegypti 346.9423 950.0453 0.0039 ± 0.0024 7.7784
2. Anopheles stephensi 124.2068 309.7531 0.0119 ± 0.0064 4.4232
3. Culex quinquefasciatus 359.4834 796.4536 0.0035 ± 0.0024 24. 4758
ppm – parts per million, Statistical significance:- With increase in concentration, the moratality rate is increasing.
Table 2: Mosquito Repellent activity of Pongamia pinnata against blood starved female
Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus.
Sl.No Concentration(%) Complete Protection Time (Min)
Aedes Anopheles Culex
aegypti stephensi quinquefasciatus
1 Control 1.02 3.7 5.8
2 0.1 20.38 41.78 40.23
3 0.5 50.98 74.08 74.23
4 1 99.96 141.35 144.73
Statistical significance:- With increase in concentration, the complete protection time is increasing
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RJPS, Apr-Jun, 2011/ Vol 1/ Issue 1