Indian Journal of Natural Products and Resources

Vol. 1(2), June 2010, pp.208-212

Larvicidal efficacy of leaf extract of two botanicals against the mosquito

vector Aedes aegypti (Diptera: Culicidae)

KM Remia and S Logaswamy*

PG and Research Department of Zoology, Kongunadu Arts and Science College, Coimbatore, Tamil Nadu, India-641 029.

Received 15 March 2009; Accepted 13 October 2009

Mosquitoes are the most important single group of insects in terms of public health. They transmit a number of diseases,

such as malaria, filariasis, dengue fever, chikungunya, Japanese encephalitis, etc. causing millions of deaths every year. The

application of easily degradable plant compounds is considered to be one of the safest methods to control insect pests and

vectors as an alternative source for the synthetic pesticides. A study was made to monitor the effect of plant extracts on

different instars of larvae and pupae of mosquito vector Aedes aegypti. Bio-assay was made using the solvent acetone to find

out the median lethal concentration (LC50). Plants, like Lantana camara Linn., Catharanthus roseus G. Don which possess

insecticidal properties, are seemed to be better vector control agents than the synthetic xenobiotics.

Keywords: Lantana camara, Catharanthus roseus, Botanicals, Mosquito vector, Aedes aegypti, Insects, Larvicides.

IPC code; Int. cl.8—A61K 36/00, A01N 25/00, A01N 65/00, A01N 65/22.

Introduction There are currently more than 300 mosquito

species in the world grouped in 39 genera and 135

subgenera. Aedes aegypti is a very important disease

vector, transmitting the arbovirus causing dengue

haemorrhagic fever (DHF) and chikungunya in

human1. At present, no effective vaccine is available

for dengue; therefore, the only way of reducing the

incidence of this disease is by mosquito control,

which is frequently dependent on applications of

conventional synthetic insecticides2.

Insect pests have been controlled with synthetic

insecticide over 50 years but problems of pesticide

resistance and negative effects on non-target

organisms, including human and environment have

been reported3. The synthetic insecticides are more

hazardous to handle, leave toxic residues in food

products and are not easily biodegradable. The world

flora has a variety of plant species and in order to

increase the number of plants used for pest control,

more studies are being carried out to identify variety

of effective substances found in different plant

species. Consequently, substances alternative of

chemical pesticides, which pollute our natural sources

and threaten our future, can be discovered. More than

2000 plant species have been known to produce

chemical factors and metabolites of values in pest

control programs and among these plants, products of

some 344 species have been reported to have a variety

of activity against mosquitoes4.

More important fact is that the plant extracts are

sometimes more effective than the synthetic pesticide

and phytochemicals have major role in mosquito

control programme5-7

. Though several plants from

different families have been reported for

mosquitocidal activity, only a very few botanicals

have moved from laboratory to the field use, like

neem based insecticides, which may be due to the

light and heat instability of phytochemicals compared

to synthetic insecticides8. An excellent review of the

activity of neem, Azadirachta indica A. Juss. and

other plants on mosquito control potential has been

published for further studies9.

Lantana camara Linn. (Family-Verbenaceae) is hairy shrub, native to tropical America, found wild and cultivated as an ornamental or hedge plant. About 8 species of Lantana occur in India and different parts of these plants are reported to be used in traditional medicine for the treatment of various human ailments such as ulcers, eczema eruptions, malaria and rheumatism

10. Catharanthus roseus G. Don belonging

to Family- Apocynaceae, grows throughout India and found in wet and sandy land, possesses high medicinal value (Plate 1).

———————

*Correspondent author

E-mail: remiabalan@gmail.com, slogaswamy@yahoo.co.in

Phone: 09952833209, 09443006007

REMIA & LOGASWAMY: LARVICIDAL EFFICACY OF LEAF EXTRACT OF TWO BOTANICALS

209

The present study was carried out to determine the

biological activities of these two plants Lantana

camara Linn. and Catharanthus roseus G. Don

against mosquito species Aedes aegypti. The result of

the present study would be useful in promoting

research aiming at the development of new agents for

mosquito control based on bioactive chemical

compounds from indigenous plant sources.

Materials and Methods Collection of plants and preservation of acetone extract of

leaves

The leaves of L. camara and C. roseus were

collected locally in and around Coimbatore identified

by experienced botanist and they were washed with

water, dried in shade at room temperature and

powdered with the help of mechanical device. The

dried powder (100g) was extracted with 300ml of

acetone solvent with a minimum of 8h up to 20h in a

Soxhlet apparatus11

. After extraction the solvent was

evaporated using vacuum evaporator to obtain the

extract in dried form. Dried residues obtained were

12g (L. camara) and 10.5g (C. roseus) of acetone

extract; they were stored in airtight desiccators and

used for experiment.

Collection and storage of experimental animals

The eggs of Aedes aegypti were collected from

National Institute for Communicable Disease Center

(NICDC), Coimbatore. The larvae were cultured and

maintained in the laboratory at 27 ± 1oC and 85% of

relative humidity. Larval forms were maintained in

tray by providing dog biscuit and yeast powder in the

3:1 ratio.

Test for larvicidal activity12

The laboratory colonies of Aedes aegypti were used

for the larvicidal activity. II and IV instar larvae and

pupae of the selected mosquito species were kept in

500ml glass beaker and different concentration of

selected plant extract was added to find out LC50.

Bioassay experiment

Different concentrations of extract (between

50ppm to 500ppm) were prepared using distilled

water. The mosquito larvae were treated with extract

by using the method of WHO13

. Ten larvae of Aedes

aegypti were introduced in different test concentration

of both plant extracts along with a set of control

containing distilled water without any test solution.

After adding the larvae, the glass dishes were kept in

laboratory at room temperature. By counting the

number of dead larvae at 24hrs of exposure, the

mortality rate and the median lethal concentration

were obtained. Five replications were maintained for

each concentration. Dead larvae were removed as

soon as possible in order to prevent decomposition,

which may cause rapid death of the remaining larvae.

The water used for the study was analyzed by using

the method of APHA14

.

The LC50 values and upper, lower confidence limit

and chi-square test were calculated according to

Probit methods of Finney15

.

Results and Discussion Physical and chemical characteristics of water used

for the study, like temperature 26.5±0.6oC, pH

7.5±

0.5, dissolved oxygen 4.5±0.4mg/l, dissolved carbon

dioxide 1.5±0.2mg/l, salinity 1.0±0.1ppt and

Plate 1: A. Lantana camara; B. Catharanthus roseus

INDIAN J NAT PROD RESOUR, JUNE 2010

210

alkalinity 129±0.6 mg/l were within the permissible

limits throughout the study periods.

The 24h bioassay is a major tool for evaluating the

toxicity of phytotoxins, and a number of researchers

have been applying this method to assess the toxic

effect of different plant extraction against

mosquitoes16,17

. The mosquito larvae exposed under

plant extracts showed significant behavioral changes.

The changes were observed within 30 minutes of

exposure. The most obvious sign of behavioral

changes observed in Aedes aegypti was inability to

come on the surface. The larvae also showed

restlessness, loss of equlibrium and finally led to

death. These behavioral effects were more

pronounced in case of C. roseus than L. camara

extracts after exposures. These effects may be due the

presence of neurotoxic compounds in both

the plants. No such behavioral changes were obtained

in control groups.

Results of the experiment conducted for evaluating

the larvicidal efficacy of both plants showed that they

are toxic to the Aedes aegypti larvae. Lethal

concentration of leaf extracts were 203.49ppm

(L. camara) and 230.76ppm (C. roseus) for the IV

instar larvae and it was 281.35ppm for pupae at 24hrs

of exposure periods. The same concentration of plant

extract gave 100% mortality after 96hrs of test period.

The leaf extracts of C. roseus showed more effect

than the L. camara. LC50 of C. roseus was 75.31ppm

for the II instar larvae, whereas it was 156.85ppm for

IV instar larvae and it was 207.83ppm for the pupae.

Zero percent of mortality was noted in control. The

Chi-square test revealed significance of the study

(Table 1). The larval II, IV instar and pupal mortality

rate was higher when exposed under C. roseus

compared to L. camara toxicity (Table 2).

Neem and Karanja oil are employed extensively in

Ayurvedic formulations for various purposes for

Table 1— Toxicity of leaf extracts of Lantana camara and

Catharanthus roseus against different stages of Aedes aegypti

under 24h exposure

95% Fiducial

Plants used

Stages of

exposure

LC 50

(ppm) Upper Lower

Chi-

square test

II instar 203.49 197.23 209.60 0.0047

IV instar 230.76 235.64 225.17 0.0052

L. camara

Pupae 281.35 287.52 275.10 0.0037

II instar 75.31 79.64 71.48 1.362

IV instar 156.85 161.79 150.64 1.145

C. roseus

Pupae 207.83 212.28 203.19 0.0049

Table 2— Percentage larval and pupal mortality of Aedes aegypti for different concentrations of leaf extract of

Lantana camara and Catharanthus roseus for 24 h exposure

Plants used

Stages of exposure

(Aedes aegypti)

Parameters

Effective concentration in ppm

Control

50

100

150

200

250

II instar

Larval Mortality

(%)

0

4

22

36

48

65

Control

200

210

220

230

240

IV instar

Larval Mortality

(%)

0

19

27

33

53

60

Control

220

240

260

280

300

L. camara

Pupae

Pupal Mortality (%)

0

11

23

29

50

65

Control

20

40

60

80

100

II instar

Larval Mortality

(%)

0

24

30

39

50

69

Control

50

100

150

200

250

IV instar

Larval Mortality

(%)

0

11

30

51

66

77

Control

190

200

210

220

230

C. roseus

Pupae

Pupal Mortality (%)

0

33

39

50

64

79

REMIA & LOGASWAMY: LARVICIDAL EFFICACY OF LEAF EXTRACT OF TWO BOTANICALS

211

years. The use of vegetable oil presents a better option

in comparison to chemical pesticides for the larval

mosquito control, as chemicals may cause

environmental hazards and proved troublesome in the

long run18

. Extensive research has been carried out on

the effect of botanical derivatives of the neem tree and

its derivatives19

.

Methanolic extract of the leaves of Atalantia

monophylla Corr. (Rutaceae) were evaluated for

mosquitocidal activity against the immature stages of

mosquitoes, Culex quinquefasciatus, Anopheles

stephensis and Aedes aegypti in the laboratory20

. A

survey of literature on control of different species of

mosquito revealed that assessment of the efficacy of

different phytochemicals obtained from various plants

has been carried out by a number of researches on the

field of vector control4 Ageratina adenophora

(Spreng.) R. M. King & H. Rob. showed toxic effects

on the mosquito species of Aedes aegypti and Culex

quinquefasciatus21

. Albizia amara Boiv. and Ocimum

sanctum Linn. showed larvicidal and repellant

properties against Aedes aegypti and neem seed kernel

extracts showed higher larvicidal activity16,22

on Aedes

aegypti. A detailed laboratory study on extracts of

fruit of Piper nigrum Linn. against larvae of Culex

pipines, Aedes aegypti and Aedes togoi was carried

out23

. The authors determined the LC50 and observed

the behavioural changes and mortality in the larvae.

Similar observations were noticed in the present study

and support the potential applications of these herbs

in mosquito control measures.

Molluscicidal and mosquito larvicidal efficacy of

Lantana indica Roxb. and mosquito larvicidal

property of Momordica charantia Linn. have already

been reported24,25

and observed them safe for human

health. These investigations support the present work.

Conclusion

As the leaf extract of L camara and C. roseus are

highly toxic even at low doses these plants may

eventually prove to be useful larvicide. Further

analysis is required to isolate the active principles and

optimum dosages, responsible for larvicidal and adult

emergence inhibition activity in Aedes aegypti. The

product of these plants can be well utilized for

preparing biocides or phytochemicals from which all

the non-target organisms can be rescued from harmful

vectors. These plants would be eco-friendly and may

serve as suitable alternative to synthetic insecticides

as they are relatively safe, inexpensive and are readily

available in many areas of the world.

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