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JOURNAL OF MOSQUITO RESEARCH
8
in term of susceptibility, 14.67% mortality was
achieved with the concentration of 50 ppm and utterly
suppressed the exposed larvae in 100 and 200 ppm
getting LC
50
and LC
90
values of 99.61 and 179.42 ppm,
respectively.
Cx. quinquefasciatus
was still the most
resistant mosquito species against the poisonous effect
of
C. rigidus
essential oil. They presented the highest
mortality rate of 69.33 and 100% only with 100 and
200 ppm, respectively.
The toxicity results of
P. glandulosus
essential oil
against early pupal stages of
Ae. aegypti
,
An. gambiae
and
Cx quinquefasciatus
24 h of exposure clearly
indicated that the oil was toxic against all the three
mosquito species tested (Table 3).
An. gambiae
was
the most susceptible mosquito pupae displaying LC
50
and LC
90
values of 22.60 and 140.53 ppm,
respectively and killing 61.33% of exposed pupae at
lower concentration (25 ppm) and 100% with 300
ppm.
Ae. aegypti
recorded mortality of 54.67% with
the lowest concentration (25 ppm) and 100% from
200 ppm.
Cx quinquefasciatus
showed higher LC
50
and LC
90
values of 104.75 and 225.05 ppm, respectively
registering no mortality at lower concentration of 25 ppm
but total suppression with 300 ppm.
Table 3 Mosquito pupicidal activity of
P. glandulosus
essential oil against
Ae. aegypti
,
An. gambiae
and
Cx quinquefasciatus
pupae
24 h post exposure
Mosquito species used
Conc.(ppm)
MM±SD (%)
LC
50
(LCL
-
UCL) (ppm)
LC
90
(LCL
-
UCL) (ppm)
χ
2
25
54.67±4.61
a
27.22
93.42
2.87
50
62.67±4.61
b
(15.24
-
37.32)
(67.96
-
168.35)
100
90.67±5.11
c
200
100.00±0.00
d
Aedes aegypti
300
100.00±0.00
d
F value
86.40***
25
61.33±6.11
a
22.60
140.53
3.92
50
65.33±4.61
a
(7.64
-
36.21)
(91.76
-
344.88)
100
76.00±5.00
b
200
96.00±4.00
c
Anopheles gambiae
300
100.00±0.00
c
F value
33.40***
25
0.00±0.00
a
104.75
225.05
3.93
50
10.67±4.61
b
(86.20
-
126.00)
(179.33
-
320.06)
100
54.67±4.61
c
200
76.00±3.00
d
Culex quinquefasciatus
300
100.00±0.00
e
F value
254.17***
Note: MM±SD (%): Mean of mortality ± standard deviation (%); MM±SD within a column followed by the same letter do not differ
significantly at P= 0.05 (Duncan’s test); ***: p<0.001; LC
50
and LC
90
: Lethal Concentrations able to kill 50% and 90% of pupae
respectively; ppm: parts per million; LCL: Lower Confidence Limit; UCL: Upper Confidence Limit; χ2: Chi-squared; Number of
replicates: 4
The results presented in Table 4 showed the mortality
of the early pupal stages of
Ae. aegypti
,
An. gambiae
and
Cx quinquefasciatus
by
C. rigidus
leaf essential
oil after 24 h of exposure. Percent mortality gradually
increased with increasing oil concentrations. With the
LC
50
of 47.63 ppm, the oil killed all the exposed
An.
gambiae
pupae at 300 ppm. The same LC
50
values of
50.95 and 307.19 ppm were observed against
Ae.
aegypti
and
Cx quinquefasciatus
, respectively Neither
larvae nor pupae survived against DDVP, the
conventional mosquitocide.
2 Discussion
Essential oil from various plants has been found to be
toxic against different mosquito species in the field of
vector control (Mann and Kaufman, 2012; Asgar, 2013).