toxicity of ocimum gratissimum leaf extract on the developmental stages of different mosquito...

Toxicity of Ocimum gratissimum leaf extract on the developmental stages

of different mosquito species.

Keywords: Effective, extracts, developmental stages, mosquito, species, mortality.

ABSTRACT: The effect of some plant extract on the developmental stages of mosquito species was conducted using Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti at the first instar, second instar, third instar, fourth instar, pupae and adult. The plant used was scentleaf (Ocimum gratissimum). Soxhlet apparatus was used to extract each pulverized plant part using petroleum ether solvent. Plant extract from the petroleum ether solvent was used to test their effects on the developmental stages of each mosquito species. The result showed that the higher the developmental stages, the lower the percentage of mortality. It was also observed that as the time and concentration increases, the percentage of mortality also increases. Generally, the result showed that Anopheles gambiae is more susceptible in the extracts used followed by Aedes aegypti and then Culex quinquefasciatus.

068-078 | JRAS | 2014 | Vol 2 | No 1

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www.janimalsciences.com

Journal of Research in Animal

Sciences An International

Scientific Research Journal

Authors:

Ebe TE1, Osuala FOU2,

Njoku OO3, Opara FN4,

Iwuala MOE5

Institution:

1. Department of

Environmental Technology,

School of Environmental

Technology, Federal

University of Technology,

Owerri, Imo state, Nigeria.

2, 3, 4 and 5. Department of

Biological Science, School

of Science, Federal

University of Technology, Owerri, Imo state, Nigeria.

Corresponding author:

Ebe TE.

Email:

Web Address: http://janimalsciences.com/

documents/AS0023.pdf. Dates: Received: 23 Sep 2013 Accepted: 22 Oct 2013 Published: 28 Feb 2014

Article Citation: Ebe TE, Osuala FOU, Njoku OO, Opara FN and Iwuala MOE. Toxicity of Ocimum gratissimum leaf extract on the developmental stages of different mosquito species. Journal of Research in Animal Sciences (2014) 2(1): 068-078.

Journal of Research in Animal Sciences An International Scientific Research Journal

Original Research

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INTRODUCTION

Since the early part of the last century,

researchers have ascertain the importance of mosquito

vectors of human pathogens. Mosquitoes have been a

constant impediment to progress, causing great suffering

on account of their blood-sucking habits and their ability

to transmit disease pathogens.

Yearly, large amounts of money is mapped out

for mosquito control which involves the use of synthetic

(artificial) pesticides; in most cases they

areorgano- chlorines, cabamates, organophosphates etc.

These chemicals have adverse effect on the environment

and man, and some are very persistent and take a long

time to breakdown and are easily moved by wind or

water to any part of the earth. Persistent pesticides have

also been discovered in animals including humans.

Another problem that is associated with persistent

chemicals used as pesticides is its bioaccumulative effect

in humans. Furthermore, some pests are resistant to

synthetic pesticides therefore, they have little or no effect

on the control of these pests which tend to impose

problem on the environment. However, extracts of some

plants with insecticidal properties have been tried in the

recent past for the control of variety of insect pests and

vectors. For instance, Ocimum gratissimum commonly

called “scent leaf” or “fever plant” is a small, smooth

shrub with many branches and are commonly found in

the tropics and widely distributed because of its

medicinal uses. Ocimum gratissimum (Scent leaves)

belongs to the family Lamiaceae and it is an aromatic

perennial herb widely grown in Nigeria. It is commonly

known as scent leaf or locally, it is called Nchuanwu by

the Igbos, Effirim by the Yorubas and Dai doyatagida by

the Hausa (Orwa et al., 2009; Okoli et al., 2010). The

plant can be used for the treatment of diseases like

malaria (Rabelo et al., 2003). Edeoga et al., 2006,

reported the presence of alkaloids and flavonoids in the

plant. There is presence of bioactive compounds like

eugenol, thymol, camphor and linolool on its leaf

essential oil (Rabelo et al., 2003; Lemos et al., 2005).

METHODOLOGY

Collection of mosquito species

The eggs of the different species of Mosquito

(Aedes aegypti, Anopheles gambiae and

Culex quinquefasciatus) were collected from the egg

colony at the National Arbovirus and Vector Research

Centre, Enugu, Enugu State, Nigeria, and were reared in

the laboratory.

Collection of plant parts

Fresh plant parts were collected at Amudi in

Ezinihitte Mbaise Local Government Area of Imo State

and identified by a botanist in Forestry and Wild Life

Department of Federal University of Technology,

Owerri. Dead leaves were removed together with insect

larvae from the twigs. The plant part was carefully

washed, rinsed with tap water and air dried at room

temperature of 28±1oC for five days and stored in air

tight glass containers for further use (Okigbo et al.,

2010).

Preparation of plant extract

The completely dried plant part was ground with

Binatone Mx10 blender and sieved to obtain a fine

powder of the plant part.150 grams of each pulverised

plant part was placed in a plain sheet of white paper, then

placed in the timbel of the soxhlet apparatus

compartment using petroleum ether extraction solvent

(Okigbo et al., 2010).

Preparation of test material

Larval and pupal stages.

Stock solution was prepared by dissolving 5g of

the extract in 150mls of water into which three drops of

acetone was added to emulsify the oil in water and then

making it up to 250ml by mixing with distilled water in

standard flask. All the test solutions were made by

pipetting 5ml-50ml of the stock solution and introduced

into 240ml, 235ml to 195ml of distilled water

respectively in separate labelled500ml bowls making it

Ebe et al.,2014

069 Journal of Research in Animal Sciences (2014) 2(1): 068-078

up to 245ml in volume (WHO, 1981 )

Adult stage

Stock solution was prepared by dissolving also

5g of the extract in 150mls of water and three drops of

acetone is added to emulsify the oil in water and then

making it up 250ml by mixing with distilled water in

standard flask. All the test solutions were made by

pipetting 5-50ml of the stock solution and impregnate a

white paper with the different concentrations of the test

plant extract. The impregnated papers were placed

separately in a plastic container of 500ml size and

covered with a mosquito net of 0.1cm mesh with a small

opening and then tied with a rubber band.

Susceptibility test

LARVA/PUPA

Twenty specimens of each stage of the different

mosquito were picked using rubber pipette and placed in

small separate specimen bottles containing 5ml of water

and then exposed to each of the concentrations of the

extract giving a final volume of 250ml in the bowls.

Quaker oat powder was used to feed the larvae

every twenty-four hours (Mbgemena, 2010). Three

replicates for each of the test concentration and control

(without plant extracts) were tested for anti-larval/pupal

effects. The larval/pupae mortalities were recorded at

intervals of 8 hours for 48 hours exposure. All the

mortalities were counted and recorded.

Adult stage

Twenty specimens from each of the mosquitoes

types were collected from the rearing cage using

aspirator and introduced into the plastic containers

containing impregnated paper of varying concentrations

(WHO, 1999, WHO, 1992 and Siriporn and Mayura,

2011); control experiment was set-up by exposing

mosquito species to an untreated paper . Each test was

performed in three replicates with simultaneous control

sets (Siriporn and Mayura, 2011).

RESULTS

From the Table 1, after 8hrs of exposture,

Anopheles gambiae recorded 100% mortality at 50mg/ml

at the first instar stage which decreases with increase in

developmental stages while both Culex quinquefasciatus

and Aedes aegypti recorded 97.5% at the same

concentration and stage which also decreases with

increase in developmental stages.

Table 2 shows that Anopheles gambiae recorded

100% mortality from 35mg/ml-50mg/ml at the first instar

stage and 50mg/ml at the second instar stage while less

than 100% mortality was recorded from the third instar-

the adult stages.

Furthermore, Aedes aegypti recorded 100%

mortality from 40mg/ml-50mg/ml at the first instar

and at 50mg/ml at the second stage and less than

100% from third instar- adult stages. Likewise, in

Culex quinquefasciatus recorded 100% mortality from

45-50mg/ml only at the first instar while from second

instar-adult stages recorded less than 100%.

In Table 3, after 24hrs exposture,

Anopheles gambiae recorded 100% mortality from first

instar to fourth instar at 25-50mg/ml, 35-50mg/ml, 45-

50mg/ml and 50mg/ml respectively.

Also Culex quinquefasciatus recorded 100%

mortality in first and second instar stages at 30-50mg/ml

and 45-50mg/ml respectively while Aedes aegypti also

recorded also 100% mortality in the first and

second instar stages at 25-50mg/ml and 35-50mg/ml

respectively.

After 32hrs of exposture, 100% mortality was

recorded in Anopheles gambiae from the first instar

pupa stages from 5 to 50mg|ml respectively.

Culex quinquefasciatus recorded 100% mortality from

the first instar to third instar stages from 20-50mg/ml,

30-50mg/ml and 50mg/ml respectively. While

Aedes aegypti recorded 100% mortality from first instar to

fourth instar stagefrom15-50mg/ml,25-50mg/ml, 45-50mg/

ml and 50mg/ml respectively. This is shown in table 4.

Ebe et al., 2014

Journal of Research in Animal Sciences (2014) 2(1): 068-078 070

Ebe et al.,2014


Table 1:Effect of Ocimum gratissimum leaf on different stages of three mosquito species after eight hours.

Mosquito species Conc. of plant Stages of mosquito species

Extract (Mg/Ml)

1 2 3 4 5 6

Anopheles gambiae

5 45.00 25.00 15.00 2.33 0.00 0.00

10 50.00 30.00 20.00 7.67 0.00 0.00

15 55.00 40.00 25.00 17.67 7.67 0.00

20 65.00 45.00 32.33 27.67 17.67 8.00

25 72.33 55.00 37.33 37.33 27.33 13.00

30 80.00 60.00 45.00 40.00 30.00 23.00

35 90.00 67.67 57.67 52.33 42.33 18.00

40 95.00 77.33 67.67 57.33 47.67 33.67

45 97.33 85.00 77.33 65.00 55.00 38.00

50 100.00 92.67 85.00 72.67 62.67 39.67

Culex quinquefasciatus

5 25.00 7.67 00.00 00.00 00.00 00.00

10 35.00 15.00 00.00 00.00 00.00 00.00

15 42.67 20.00 2.67 00.00 00.00 00.00

20 55.00 25.00 7.67 2.67 00.00 00.00

25 60.00 35.00 12.67 5.00 2.33 00.00

30 65.00 45.00 20.00 10.00 7.33 00.00

35 72.67 55.00 25.00 20.00 12.33 3.00

40 82.67 60.00 30.00 27.33 20.00 8.00

45 92.67 70.00 40.00 32.33 25.00 14.67

50 97.33 75.00 45.00 40.00 30.00 19.67

Aedes aegypti

5 32.33 20.00 2.33 00.00 00.00 00.00

10 40.00 25.00 5.00 00.00 00.00 00.00

15 50.00 30.00 7.67 2.67 00.00 00.00

20 60.00 40.00 12.33 7.67 2.33 00.00

25 65.00 45.00 17.67 12.67 7.67 00.00

30 70.00 50.00 27.33 20.00 17.67 1.33

35 77.33 65.00 35.00 27.33 22.67 9.67

40 85.00 70.00 45.00 37.67 27.67 13.00

45 90.00 75.00 47.67 42.67 32.67 19.67

50 97.67 85.00 60.00 52.67 42.33 24.33

Ebe et al.,2014


Mosquito species Conc. of plant extract Different stages of mosquito species

1 2 3 4 5 6

Anopheles gambiae 5 65.00 45.00 37.67 20.00 10.00 00.00

10 70.00 50.00 45.00 27.67 17.33 00.00

15 75.00 60.00 55.00 32.67 22.67 1.00

20 80.00 65.00 60.00 47.67 37.67 11.00

25 87.67 75.00 67.33 55.00 45.00 16.00

30 95.00 80.00 72.67 62.67 52.67 26.00

35 100.00 85.00 77.33 70.00 60.00 31.00

40 100.00 90.00 82.67 77.33 67.67 37.67

45 100.00 97.67 92.67 82.33 72.67 41.00

50 100.00 100.00 97.33 92.67 82.67 42.67

Culex quinquefasciatus 5 45.00 30.00 2.33 2.67 00.00 00.00

10 55.00 35.00 7.67 7.33 2.33 00.00

15 60.00 47.67 12.67 15.00 7.67 00.00

20 70.00 52.33 25.00 20.00 12.67 00.00

25 80.00 57.33 30.00 25.00 17.33 00.00

30 85.00 70.00 35.00 30.00 22.67 2.67

35 92.67 75.00 45.00 37.33 32.67 6.00

40 97.33 80.00 50.00 42.67 37.67 11.00

45 100.00 90.00 60.00 47.67 42.33 17.67

50 100.00 95.00 65.00 60.00 47.33 22.67

Aedes aegypti 5 50.00 40.00 20.00 2.33 2.33 00.00

10 60.00 45.00 25.00 7.33 7.67 00.00

15 67.67 50.00 30.00 20.00 20.00 00.00

20 75.00 60.00 37.67 25.00 25.00 00.00

25 85.00 65.00 45.00 30.00 30.00 00.00

30 90.00 70.00 50.00 35.00 35.00 4.33

35 95.00 85.00 57.67 45.00 45.00 12.67

40 100.00 92.67 62.33 55.00 55.00 16.00

45 100.00 95.00 70.00 60.00 60.00 22.67

50 100.00 100.00 77.67 67.67 57.67 29.33

Table 2: Effect of Ocimum gratissimum leaf on different stages of mosquito species after sixteen hours

Ebe et al.,2014

Mosquito species Conc. of plant extract (mg/ml) Different stages of mosquito species

1 2 3 4 5 6


10 90.00 70.00 70.00 52.67 40.00 1.67

15 95.00 80.00 75.00 57.67 45.00 5.00

20 97.33 85.00 80.00 62.67 50.00 15.00

25 100.00 95.00 85.00 75.00 62.33 20.00

30 100.00 97.33 90.00 80.00 72.67 30.00

35 100.00 100.00 92.67 85.00 75.00 35.00

40 100.00 100.00 95.00 90.00 80.00 41.67

45 100.00 100.00 100.00 97.33 87.33 45.00

50 100.00 100.00 100.00 100.00 92.67 46.67

Culex

Quinquefasciatus 5 65.00 50.00 20.00 12.33 12.67 00.00

10 75.00 55.00 25.00 20.00 17.33 00.00

15 80.00 67.67 32.67 32.67 30.00 00.00

20 85.00 75.00 40.00 40.00 37.33 00.00

25 97.67 80.00 50.00 45.00 42.33 3.33

30 100.00 90.00 55.00 50.00 47.33 6.67

35 100.00 95.00 65.00 55.00 52.67 10.00

40 100.00 97.33 70.00 60.00 57.67 15.00

45 100.00 100.00 80.00 67.33 62.33 21.67

50 100.00 100.00 85.00 77.67 62.33 26.67

Aedes aegypti 5 70.00 57.33 40.00 12.67 12.33 00.00

10 80.00 62.67 50.00 25.00 22.67 00.00

15 85.00 67.33 55.00 37.33 37.67 00.00

20 95.00 72.33 60.00 45.00 42.33 00.00

25 100.00 77.67 65.00 50.00 47.33 3.33

30 100.00 92.33 70.00 55.00 52.67 8.33

35 100.00 100.00 75.00 60.00 57.67 16.67

40 100.00 100.00 80.00 70.00 67.33 20.00

45 100.00 100.00 85.00 75.00 72.33 26.67

50 100.00 100.00 95.00 85.00 75.00 33.33

Table 3: Effect of Ocimum gratissimum leaf on different stages of mosquito species after twenty four hours.


Ebe et al.,2014



1 2 3 4 5 6


10 100.00 90.00 80.00 65.00 55.00 8.33

15 100.00 97.33 87.67 77.67 65.00 15.00

20 100.00 97.67 92.33 82.33 70.00 25.00

25 100.00 100.00 97.33 85.00 77.33 31.67

30 100.00 100.00 97.67 92.67 82.33 38.33

35 100.00 100.00 100.00 97.67 87.67 45.00

40 100.00 100.00 100.00 100.00 92.33 50.00

45 100.00 100.00 100.00 100.00 97.33 51.67

50 100.00 100.00 100.00 100.00 100.00 58.33

Culex

quinquefasciatus 5 80.00 67.67 37.33 22.67 22.33 00.00

10 87.33 72.33 45.00 32.33 32.67 00.00

15 97.33 82.67 50.00 45.00 40.00 3.33

20 100.00 92.33 57.67 52.67 50.00 6.67

25 100.00 97.33 67.67 62.67 57.67 13.33

30 100.00 100.00 75.00 70.00 62.67 20.00

35 100.00 100.00 85.00 75.00 67.33 25.00

40 100.00 100.00 90.00 80.00 67.67 28.33

45 100.00 100.00 95.00 85.00 72.33 36.67

50 100.00 100.00 100.00 92.67 77.33 41.67

Aedes aegypti 5 90.00 75.00 57.67 30.00 27.33 00.00

10 97.67 80.00 62.33 40.00 37.33 1.67

15 100.00 90.00 67.67 55.00 52.67 3.33

20 100.00 95.00 72.67 60.00 57.67 6.67

25 100.00 100.00 77.33 65.00 62.33 13.33

30 100.00 100.00 82.33 75.00 72.33 20.00

35 100.00 100.00 92.33 80.00 77.33 28.33

40 100.00 100.00 97.33 87.67 82.33 31.67

45 100.00 100.00 100.00 95.00 87.67 38.33

50 100.00 100.00 100.00 100.00 92.33 45.00

Table 4: Effect of Ocimum gratissimum leaf on different stages of mosquito species after thirty two hours

Ebe et al.,2014


1 2 3 4 5 6

Anopheles gambiae

5 100.00 97.67 82.67 70.00 57.33 8.33

10 100.00 100.00 90.00 77.33 67.67 15.00

15 100.00 100.00 95.00 82.67 72.67 20.00

20 100.00 100.00 97.67 90.00 82.67 28.33

25 100.00 100.00 100.00 95.00 87.33 36.67

30 100.00 100.00 100.00 97.67 92.33 40.00

35 100.00 100.00 100.00 100.00 97.33 51.67

40 100.00 100.00 100.00 100.00 100.00 56.67

45 100.00 100.00 100.00 100.00 100.00 65.00

50 100.00 100.00 100.00 100.00 100.00 75.00

Culex

quinquefasciatus

5 97.33 85.00 47.33 37.67 37.67 00.00

10 100.00 90.00 57.33 45.00 42.33 1.67

15 100.00 97.33 65.00 62.33 47.33 8.33

20 100.00 100.00 75.00 70.00 57.33 16.67

25 100.00 100.00 85.00 75.00 67.67 23.33

30 100.00 100.00 95.00 87.67 72.67 30.00

35 100.00 100.00 100.00 92.67 77.67 36.67

40 100.00 100.00 100.00 97.67 82.67 41.67

45 100.00 100.00 100.00 100.00 87.67 50.00

50 100.00 100.00 100.00 100.00 92.33 56.67

Aedes aegypti

5 100.00 90.00 70.00 45.00 42.33 1.67

10 100.00 95.00 75.00 60.00 52.33 3.33

15 100.00 100.00 80.00 72.33 62.33 6.67

20 100.00 100.00 85.00 80.00 77.67 15.00

25 100.00 100.00 95.00 85.00 80.00 21.67

30 100.00 100.00 97.67 92.33 87.67 28.33

35 100.00 100.00 100.00 97.33 90.00 36.67

40 100.00 100.00 100.00 100.00 92.67 45.00

45 100.00 100.00 100.00 100.00 97.67 56.67

50 100.00 100.00 100.00 100.00 100.00 65.00

Table 5: Effect of Ocimum gratissimum leaf on different stages of mosquito species after forty hours


Ebe et al.,2014



1 2 3 4 5 6

Anopheles gambiae 5 100 100.00 95.00 80.00 70 21.67

10 100 100.00 100.00 90.00 77.67 28.33

15 100 100.00 100.00 97.33 87.33 36.67

20 100 100.00 100.00 100.00 92.67 43.33

25 100 100.00 100.00 100.00 97.67 50.00

30 100 100.00 100.00 100.00 100.00 65.00

35 100 100.00 100.00 100.00 100.00 70.00

40 100 100.00 100.00 100.00 100.00 75.00

45 100 100.00 100.00 100.00 100.00 80.00

50 100 100.00 100.00 100.00 100.00 90.00

Culex

quinquefasciatus 5 100 97.36 65.00 47.33 47.33 3.33

10 100 100.00 75.00 57.33 55.00 8.33

15 100 100.00 85.00 72.33 60.00 16.67

20 100 100.00 95.00 87.67 65.00 21.67

25 100 100.00 100.00 95.00 77.33 31.67

30 100 100.00 100.00 97.67 85.00 38.33

35 100 100.00 100.00 100.00 90.00 45.00

40 100 100.00 100.00 100.00 92.67 53.33

45 100 100.00 100.00 100.00 97.33 60.00

50 100 100.00 100.00 100.00 100.00 68.33

Aedes aegypti 5 100 100.00 82.67 65.00 62.33 3.33

10 100 100.00 87.67 75.00 67.33 11.67

15 100 100.00 95.00 87.67 77.67 15.00

20 100 100.00 97.67 95.00 87.33 23.33

25 100 100.00 100.00 97.33 90.00 31.67

30 100 100.00 100.00 100.00 95.00 35.00

35 100 100.00 100.00 100.00 95.00 48.33

40 100 100.00 100.00 100.00 100.00 56.67

45 100 100.00 100.00 100.00 100.00 68.33

50 100 100.00 100.00 100.00 100.00 76.67

Table 6: Effect of Ocimum gratissimum leaf on different stages of mosquito species after forty eight hours.

Moreover, after 40 hours of exposure,

Anopheles gambiae and Aedes aegypti showed 100%

mortality from the first instar to pupae stages. The first

instar recorded 100% mortality in both species from

5-50mg/ml while the concentration in the other stages

varied. Culex quinquefasciatus recorded 100% mortality

from the first instar to fourth instar stages at varying

concentration as shown in table 5. The same is applicable

to the result obtained after 48hrs of exposure except that

100% mortality was recorded from 5-50mg/ml in both

the first and second instar stages of both

Anopheles gambiae and Aedes aegypti and from 5-50mg/

ml at the first instar stage of Culex quinquefasciatus.

DISSCUSION

The present study confirmed that the plant part

extract used was a potential agent for the control of

mosquito population. The intensive use of synthetic

organic chemical larvicide or adulticide produce side

effects on many beneficial insects and also poses both

acute and chronic threat to the environment and also

resistance in major vector species. Toxicity of the tested

plant extracts against the four instars of larvae, pupae

and adult of Anopheles gambiae, Culex quinquefaciatus

and Aedes aegypti varied according to the concentration

of the extract, the developmental stage, the species of

mosquito exposed and the duration of exposure. The

percentage mortality decreases by the stage of growth

with more deaths in Anopheles gambiae followed by

Aedes aegypti and then Culex quinquefaciatus. This is

because Anopheles gambiae breed and thrive well in

fresh water unlike the Culex quinquefasciatus that thrives

in polluted water and thereby having more resistance to

the extracts used (Subra, 1980). The mortality rate

decreases with increase in growth; this means that the

highest mortality occurred at the first instars of the

mosquito species with different extract while the least

occurred at the adult stage. Similar results were also

obtained by Murugan and Jeyabalan (1999) and

Prophiro et al., (2008). This may be due to its feeding

habit. The larvae feed voraciously in water (Donald

2008); so during the course of their feeding they take

more of the extract and also the toxic environment affect

with them, while the pupae and adult do not take enough

of the extract because they are not feeding on the extract

but are affected by the toxic environment only. Senthil

Kumar et al., (2009) reported that lethality varied by type

of mosquito and extract: C. citratus, Justicia gendarussa

and Centella asiatica were found to be most effective

against Anopheles stephensi, C. citratus showed toxicity

against Culex quniquefasciatus larvae giving 100%

protection for up to 5 hours at a concentration of 5.0mg/

cm2 (Siriporn and Mayura, 2011).

Furthermore, Vatandoost and Vaziri (2004) also

reported that the mortality rate in Anopheles stephensi is

higher than Culex quinquefasciatus using A. indica leaf

extract.

Virendra et al., (2009) also recorded high

mortality in Anopheles stephensi followed by

Aedes aegypti and Culex quinquefasciatus using

A. indica oil. Application of the A. indica oil formulation

at the rate of 140mg/m2 in pit tanks and drains provided

above 90% reduction of Culex larvae up to one week

whereas 100% reduction was observed in Anopheles

larvae up to two weeks (Virendra et al., 2009). This is

more evident in our research findings too.

CONCLUSION

The extract is easy to prepare and it is a safe and

cheap natural product to be used to suppress mosquito

population. The early developmental stages are more

susceptible to the extracts than the later developmental

stages and since they (larvae and pupae) cluster at a

place, it is easier to kill and control than the adult stage

in which they disperse. Therefore, the use of plant

extracts especially Ocimum gratissimum in the control of

mosquito vector associated with human diseases is

highly recommended.

Ebe et al., 2014


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