journal of entomology and zoology studies 2017; 5(5): …€¦ · ~ 522 ~ journal of entomology and...

~ 518 ~

Journal of Entomology and Zoology Studies 2017; 5(5): 518-524

E-ISSN: 2320-7078

P-ISSN: 2349-6800

JEZS 2017; 5(5): 518-524

© 2017 JEZS

Received: 25-07-2017

Accepted: 26-08-2017

Lokesh KV

Department of Zoology,

Madras Christian College,

Chennai, Tamil Nadu, India.

Kanmani S




Adline JD




Raveen R




Samuel T




Arivoli S


Thiruvalluvar University,

Vellore, Tamil Nadu, India.

Jayakumar M


University of Madras,


Correspondence

Dr. Raveen R

Associate Professor,




[email protected]

Adulticidal activity of Nicotiana tabacum

Linnaeus (Solanaceae) leaf extracts against the

sweet potato weevil Cylas formicarius Fabricius

1798 (Coleoptera: Brentidae)

Lokesh KV, Kanmani S, Adline JD, Raveen R, Samuel T, Arivoli S and

Jayakumar M

Abstract Sweet potato, Ipomoea batatas (Linnaeus) Lam. (Convolvulaceae), is a major staple food in several

regions of the world. This crop is likely to make a growing contribution to the global food system as it

plays a vital role in human diet. The sweet potato weevil, Cylas formicarius Fabricius (Coleoptera:

Brentidae) is considered to be the single most destructive pest of Ipomoea batatas globally, particularly

in the tropics and subtropics. The damage caused by this pest severely reduces the yield and greatly

affects the tubers. Control measures for this pest involves application of chemical and synthetic

insecticides, however the world is facing severe ecological challenges due to its use. Plants containing

active insecticidal phytochemicals are gaining attention because of their broad spectrum insecticidal

activity, safety, biodegradability and integrated crop management approaches as they are probable

candidates for alternatives to chemical and synthetic insecticides. In the present study, the crude solvent

(hexane, petroleum ether, dichloromethane, chloroform, ethyl acetate, acetone, methanol and aqueous)

leaf extracts of Nicotiana tabacum were tested for their efficacy against the adults of Cylas formicarius at

concentrations of 0.625, 1.25, 2.50, 5.00, 10.00 and 20.00µg/insect by the petridish bioassay method.

Adult mortality was calculated 24, 48 and 72 hours after exposure. Overall assessment of the results

indicated the chloroform and acetone extract of Nicotiana tabacum leaves to exhibit the highest activity

against the adults of Cylas formicarius with one hundred per cent adult mortality after 72 hours of

exposure and their LD50 and LD90 values were 0.49 and 0.81; 1.67 and 4.34µg/insect respectively.

However, further studies are needed to make these phytopesticides more effective and to investigate their

efficacy under field conditions since it is a well-known fact that the results of laboratory experiments

cannot be transferred uncritically into conditions which hold for the environment.

Keywords: Cylas formicarius, Ipomoea batatas, adulticidal, Nicotiana tabacum, leaf extracts

Introduction Sweet potato, Ipomoea batatas (Linnaeus) Lam. (Convolvulaceae), (Figure 1A) a

dicotyledonous plant and a tuberous root crop which originated in Central America [1] is a

major staple food in several regions of the world [2, 3]. It is cultivated in over one hundred

developing countries and ranks sixth in the world among the most important food crop

consumed after rice, wheat, potato, maize and cassava [4, 5]. Approximately 92% of world’s

sweet potato is produced in Asia with China being the largest producer worldwide [6]. This

crop is likely to make a growing contribution to the global food system as it plays a vital role

in the human diet as a rich source of energy in the form of starch and Vitamin A [7, 8]. It is also

used as animal feed in many developing countries [9]. The sweet potato weevil, Cylas

formicarius Fabricius (Coleoptera: Brentidae) (Figure 1B) is considered to be the single most

destructive pest of Ipomoea batatas [10] globally [11], particularly in the tropics and subtropics [12] both in field and storage [13, 14]. This pest has been associated with sweet potato since

1500’s and the damage caused by this pest severely reduces the yield and greatly affects the

tubers (Figure 1C & D) [15].

Cylas formicarius damage to Ipomoea batatas is devastating, since they complete their entire

life cycle within this plant [13]. The mature females lay their eggs at the base of vines or in

tubers, besides they also oviposit within the cavities excavated either in stems or tubers where

the grubs develop.

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Journal of Entomology and Zoology Studies

The white grubs (Figure 2A) feed and tunnels through the

tubers and vines which gets filled with excrement resembling

saw dust and thereby produces a terpene odour in addition to

the bitter taste and flavour that renders the sweet potato

unsuitable for human and livestock consumption [16]. The

adults prefer to live in the canopy of vines and leaves and feed

on tender buds, leaves, vines and tubers (Figure 2C). Injury

leads to thickening and cracking of stems and also to

secondary infections by microbes [17] which cause extensive

rotting of tubers (Figure 2D & E). Control measures for this

pest involves application of chemical and synthetic

insecticides like dimethoate, methamidophos and dieldrin [15]

however, the world is facing severe ecological challenges due

to its use. Plants containing active insecticidal phytochemicals

are gaining attention because of their broad spectrum

insecticidal activity, safety, biodegradability and integrated

crop management approaches as they are probable candidates

for alternatives of chemical and synthetic insecticides [18-21]. A

study reported by Palaniswami and Mohandas [22] found the

use of tobacco decoction toxic to the sweet potato weevils and

its action lasted for two weeks. Hence, usage of Nicotiana

tabacum leaf extracts was taken up for the present study.

Therefore, keeping in view of the above mentioned factors,

the present study was aimed at controlling this pest using

plant extracts as management of Cylas formicarius which is a

major issue faced by all the sweet potato producing countries

in the world.

Materials and methods

Plant collection and preparation of phytoextracts

Mature and healthy leaves of Nicotiana tabacum (Solanaceae)

were collected from Tamil Nadu, India. Taxonomical identity

of the plant was confirmed at Department of Plant Biology

and Plant Biotechnology, Madras Christian College, Chennai,

Tamil Nadu, India. The leaves were then brought to the

laboratory, washed in dechlorinated water, shade dried and

powdered with the aid of an electric blender. The powdered

leaves (1Kg) were extracted with different solvents (3L) each

viz., hexane, petroleum ether, dichloromethane, chloroform,

ethyl acetate, acetone, methanol and distilled water in a

Soxhlet apparatus [23]. The crude solvent leaf extract thus

obtained was then stored in air tight amber coloured bottles at

4°C for bioassay.

Culture of Cylas formicarius

Cylas formicarius were obtained from weekly collections of

infested tubers taken from fields and tubers infested in the

laboratory. Adults were removed from emergence cages and

placed in separate cylindrical glass jars (29cm depth and

25cm diameter) covered with a fine muslin cloth on a daily

basis. The adults were reared at 28 ±2°C, 65-70% relative

humidity under a photoperiod of 12 hours light and dark cycle

provided with fresh sweet potato tubers.

Adulticidal bioassay Mason et al. [24] methodology of petridish bioassay was

adopted with minor changes for the present study against the

adults of Cylas formicarius. Petridish bioassays were

conducted on two week old adults. For the bioassay, the F1

generation of the adults from the culture was used. Ten

unsexed adults were placed inside glass petridishes (9.5cm

diameter) whose lower dish inner surface was placed with a

Whatman No. 1 filter paper treated with different

concentrations of the plant extracts and thereafter the upper

dish was closed (Figure 2F). Tests were carried at

concentrations of 0.625, 1.25, 2.50, 5.00, 10.00 and

20.00µg/insect. Petridishes containing the treated adults were

then placed on a laboratory bench in the rearing room and

mortality was determined 24, 48 and 72 hours after exposure.

Moribund individuals were scored dead if they showed no

signs of movement. Tween 80 treated filter paper was used as

a treated control and the filter paper which received neither

plant extract nor Tween 80 but distilled water served as

untreated control. A total of three trials with three replicates

per trial were carried out.

Statistical analysis

Data from all replicates were pooled for statistical analysis.

ANOVA was performed to determine the difference in adult

mortality between concentrations. Results with P<0.05 level

were considered to be statistically significant. LD50 and LD90

values were calculated using SPSS software by probit analysis [25].

Results

The crude solvent leaf extracts of Nicotiana tabacum showed

adulticidal activity against Cylas formicarius. No adult

mortality was observed in untreated and treated control. High

per cent adult mortality was showed by the crude acetone

(86.7%) extract followed by methanol (76.7%) at the highest

concentration after 24 hours of exposure (Table 1; Figure 3A)

and their respective LD50 and LD90 values were 10.19 and

19.07; 10.29 and 23.27µg/insect (Table 4; Figure 3D). In the

case of 48 hours, it was again the acetone (93.3%) extract

which exhibited highest per cent adult mortality but was

followed by chloroform (83.3%) at the highest concentration

(Table 2; Figure 3B) and their respective LD50 and LD90

values were 4.71 and 12.68; 5.74 and 17.70µg/insect (Table 4;

Figure 3E). Whereas, after 72 hours of exposure, one hundred

per cent adult mortality was observed in chloroform, acetone,

petroleum ether and methanol extract at 1.25, 5.00, 20.00 and

20.00µg/insect respectively (Table 3; Figure 3C). Their

corresponding LD50 and LD90 values were 0.49 and 0.81; 1.67

and 4.34; 2.40 and 4.17; 2.80 and 6.74µg/insect (Table 4;

Figure 3F). Overall assessment indicated the chloroform and

acetone extract of Nicotiana tabacum to exhibit the highest

adulticidal activity against Cylas formicarius.

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Fig 1

A: Healthy Ipomoea batatas tuber;

B: Cylas formicarius adult;

C & D: Ipomoea batatas tubers infested with adults of Cylas formicarius

A D

C

B

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Fig 2: A: Cylas formicarius grub; B: Cylas formicarius pupa; C: Cylas formicarius adult

feeding on Ipomoea batatas tubers; D & E: Infested and rotten Ipomoea batatas tubers;

F: Petridish bioassay method

C

E D

F

A

B

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Table 1: Adulticidal activity of Nicotiana tabacum leaf extracts against Cylas formicarius at 24 hours

Solvent extracts Concentration (µg/insect)

UC TC 0.625 1.25 2.50 5.00 10.00 20.00

Hexane 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 0.34 ±0.58ab 0.34 ±0.58ab 1.00 ±0.00bc 1.00 ±0.00bc 1.67 ±0.58c

Petroleum ether 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 0.67 ±0.58ab 0.66 ±0.58ab 2.67 ±2.89abc 4.00 ±2.65bc 6.00 ±1.00c

Dichloromethane 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 0.67 ±0.58ab 1.00 ±0.00b 2.33 ±0.58c 4.00 ±0.00d 4.68 ±0.58d

Chloroform 0.00 ±0.00a 0.00 ±0.00a 0.33 ±0.58ab 1.33 ±0.57ab 1.67 ±0.58ab 3.33 ±0.58bc 5.33 ±3.51c 6.00 ±0.00c

Ethyl acetate 0.00 ±0.00a 0.00 ±0.00a 0.33 ±0.58a 1.00 ±0.00ab 1.33 ±0.58abc 2.33 ±0.58bcd 2.67 ±0.58cd 3.00 ±1.00d

Acetone 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 1.33 ±0.58b 2.68 ±0.58c 3.33 ±0.58c 5.33 ±0.58d 8.67 ±0.58e

Methanol 0.00 ±0.00a 0.00 ±0.00a 2.00 ±1.73ab 2.34 ±0.58abc 3.67 ±0.58bc 4.67 ±1.15bc 5.00 ±1.73cd 7.67 ±1.53d

Aqueous 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 0.67 ±0.58ab 1.33 ±0.58b 2.33 ±0.58c

UC: Untreated control; TC: Treated control; Values are mean of three replicates of three trials ±standard deviation; Different superscript

alphabets indicate statistical significant difference at P<0.05 level by one way ANOVA followed by TUKEY test performed



UC TC 0.625 1.25 2.50 5.00 10.00 20.00

Hexane 0.00 ±0.00a 0.00 ±0.00a 0.33 ±0.58ab 1.33 ±0.58ab 1.68 ±0.58b 3.33 ±0.58c 4.00 ±1.00c 4.68 ±0.58c

Petroleum ether 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 0.68 ±0.58a 2.00 ±1.00a 6.67 ±2.89b 8.33 ±1.53b 9.00 ±1.00b

Dichloromethane 0.00 ±0.00a 0.00 ±0.00a 1.00 ±0.00b 2.00 ±1.00c 2.33 ±0.58c 3.67 ±0.58d 6.00 ±0.00e 6.67 ±0.58e

Chloroform 0.00 ±0.00a 0.00 ±0.00a 4.00 ±2.65b 4.67 ±1.15bc 5.00 ±1.00bcd 6.33 ±2.31bcd 8.00 ±1.00cd 8.33 ±0.58d

Ethyl acetate 0.00 ±0.00a 0.00 ±0.00a 1.33 ±0.58ab 2.67 ±1.15b 3.33 ±0.58c 3.33 ±0.58c 3.67 ±0.58c 4.00 ±1.00c

Acetone 0.00 ±0.00a 0.00 ±0.00a 3.00 ±1.73b 3.67 ±1.15c 6.33 ±0.58d 6.33 ±0.58d 8.67 ±1.15e 9.33 ±0.58e

Methanol 0.00 ±0.00a 0.00 ±0.00a 3.33 ±2.08ab 3.67 ±1.53b 4.33 ±0.58b 6.00 ±1.00bc 6.33 ±2.31bc 8.67 ±1.53c

Aqueous 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 0.33 ±0.58a 0.68 ±0.58a 1.00 ±1.00ab 1.33 ±0.58ab 2.67 ±1.53b


alphabets indicate statistical significant difference at P<0.05 level by one way ANOVA followed by TUKEY test performed.



UC TC 0.625 1.25 2.50 5.00 10.00 20.00

Hexane 0.00 ±0.00a 0.00 ±0.00a 0.67 ±1.15a 3.00 ±0.00b 3.33 ±0.58b 4.68 ±0.58bc 6.00 ±1.00cd 7.00 ±1.00d

Petroleum ether 0.00 ±0.00a 0.00 ±0.00a 2.33 ±0.58b 2.68 ±1.15bc 3.67 ±1.15c 10.00 ±1.00d 10.00 ±0.00d 10.00 ±0.00 d

Dichloromethane 0.00 ±0.00a 0.00 ±0.00a 2.67 ±1.53b 4.00 ±2.00bc 4.68 ±0.58bc 6.00 ±0.00cd 7.67 ±0.58d 8.00 ±0.00d

Chloroform 0.00 ±0.00a 0.00 ±0.00a 8.00 ±2.00b 10.00 ±0.00c 10.00 ±0.00c 10.00 ±0.00c 10.00 ±0.00c 10.00 ±0.00c

Ethyl acetate 0.00 ±0.00a 0.00 ±0.00a 3.33 ±0.58b 5.33 ±0.58c 5.33 ±0.58c 5.68 ±0.58c 6.67 ±0.58cd 8.00 ±0.00d

Acetone 0.00 ±0.00a 0.00 ±0.00a 4.67 ±1.53b 5.33 ±0.58b 9.33 ±0.58c 9.33 ±0.58c 9.67 ±0.58c 10.00 ±0.00c

Methanol 0.00 ±0.00a 0.00 ±0.00a 4.33 ±2.52b 5.00 ±1.00bc 5.33 ±1.00bc 7.33 ±0.58cd 9.67 ±0.58de 10.00 ±0.00e

Aqueous 0.00 ±0.00a 0.00 ±0.00a 0.00 ±0.00a 1.00 ±1.00bc 1.67 ±0.58bc 2.67 ±0.58bc 3.33 ±1.15c 3.33 ±2.52c


alphabets indicate statistical significant difference at P<0.05 level by one way ANOVA followed by TUKEY test performed.

Table 4: Probit analysis of Nicotiana tabacum leaf extracts against

the adults of Cylas formicarius

Solvent extracts

Hours

24 48 72

Concentration (µg/insect)

LD50 LD90 LD50 LD90 LD50 LD90

Hexane 33.92 55.18 17.36 33.64 10.70 23.82

Petroleum ether 15.31 26.81 6.91 14.50 2.40 4.17

Dichloromethane 17.65 31.46 11.95 24.77 7.00 19.06

Chloroform 13.82 26.67 5.74 17.70 0.49 0.81

Ethyl acetate 24.82 46.09 20.39 45.84 6.83 20.93

Acetone 10.19 19.07 4.71 12.68 1.67 4.34

Methanol 10.29 23.27 7.02 18.50 2.80 6.74

Aqueous 26.38 40.57 27.03 44.47 21.97 41.20

LD50: Lethal concentration that kills 50% of the exposed adult;

LD90: Lethal concentration that kills 90% of the exposed adult

Discussion

Insect pests are a nuisance to man with respect to agriculture.

They affect food crops under field conditions as well as in

storage resulting in severe revenue loss. Conventional

pesticides have not only become less effective, as target insect

populations have developed resistance, but also kill non-target

species and natural enemies of many insect pests [26]. An

overview of research in sweet potato weevil management

during the last two decades has been reviewed by Korada et

al. [27]. Although Cylas formicarius has no record of chemical

and synthetic pesticide resistance, it may occur in the future

and thereby by way of abundant caution, the eco-friendly

phytochemicals were used in the present study viz., Nicotiana

tabacum leaf extracts and the results showed that they could

cause adult mortality of Cylas formicarius. It has been

reported by Leng and Reddy [28] that due to the cryptic nature

of the larvae, the phytochemicals may not be effective in

bringing down the larval population, but by killing or

interfering with adults they can prevent oviposition on sweet

potato crops which has been corroborated in the present study.

Botanical pesticides are effective against insect pests and have

been reported to possess insecticidal activity against this pest.

The results of the present study revealed the chloroform and

acetone extracts of Nicotiana tabacum leaves to exhibit the

highest activity against the adults of Cylas formicarius with

one hundred per cent adult mortality after 72 hours of

exposure and their LD50 and LD90 values were 0.49 and 0.81;

1.67 and 4.34µg/insect which are comparable with other

reports. An extract of the gum from leaves and twigs of

Croton linearis, contains a diterpene compound, which

showed marked insecticidal activity to the adults of Cylas

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formicarius elegantulus with a LD50 value of 0.32μg/insect

after 72 hours of exposure [29]. Sesquiterpene furan and

epingaione isolated by guided isolation of the crude ethanol

extract of the leaves and stems of Bontia daphnoides were

found to have insecticidal properties to Cylas formicarius [30].

Williams [31] evaluated the toxicity of Rhizophora mangle

extract and found them toxic to Cylas formicarius (LC50

70μg/insect) since the extract was reported to contain

triterpenoids. Jayaprakas et al. [32] demonstrated the

insecticidal effects of petroleum ether fraction of cassava seed

against Cylas formicarius with 86.7% adult mortality. The

essential oil of leaves, stem and fruits of Hyptis capitata

dominated by sesquiterpenes exhibited an LD50 of 55μg/insect

for leaves and stems and LD50 of 60μg/insect for fruits after

72 hours of exposure [33]. Hexane extract of Cleome viscosa

leaves and stem showed pyrethroid type of contact

insecticidal activity with 60% knock down effect and the

LD50 was 89.0µg/insect [34].

In the present study, observations on the adult weevil on

exposure to the leaf extracts of Nicotiana tabacum showed

signs of distress viz., sporadic bursts of running,

uncoordinated locomotory movements, stiffened legs causing

staggered walk followed by complete paralysis, necrosis and

death of the adult on exposure to 72 hours. The above

mentioned symptoms are characteristics of neurotoxic

insecticides as the phytochemical insecticides could have

gained entry into the weevil through legs and spiracles as

contact and respiratory poison. Mathur [35] reported that

Nicotiana tabacum contains nicotine which is a contact

insecticide but act principally as a fumigant and a stomach

poison for vegetable and fruit pests which are soft bodied and

minute which has been corroborated in the findings of the

present study. The present study concludes that botanical

extracts are promising candidates as environmentally friendly

pesticides that can be compatible with Cylas formicarius IPM

programs, hence may potentially substitute harmful broad

spectrum pesticides in the control of this insect pest.

However, further studies are needed to make these

phytopesticides more effective and to investigate their

efficacy under field conditions because Jagers Op Akkerhuis

et al. [36] specifically reported that it is a well-known fact that

the results of laboratory experiments cannot be transferred

uncritically into conditions which hold for the environment.

Fig 3: Per cent adult mortality of Cylas formicarius on exposure to Nicotiana tabacum leaf extracts at A: 24; B: 48 and C:

72 hours. D, E and F indicates probit analysis of Nicotiana tabacum leaf extracts against the adults of Cylas formicarius at

24, 48 and 72 hours respectively

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