~ 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
Department of Zoology,
Madras Christian College,
Chennai, Tamil Nadu, India.
Adline JD
Department of Zoology,
Madras Christian College,
Chennai, Tamil Nadu, India.
Raveen R
Department of Zoology,
Madras Christian College,
Chennai, Tamil Nadu, India.
Samuel T
Department of Zoology,
Madras Christian College,
Chennai, Tamil Nadu, India.
Arivoli S
Department of Zoology,
Thiruvalluvar University,
Vellore, Tamil Nadu, India.
Jayakumar M
Department of Zoology,
University of Madras,
Chennai, Tamil Nadu, India.
Correspondence
Dr. Raveen R
Associate Professor,
Department of Zoology,
Madras Christian College,
Chennai, Tamil Nadu, India.
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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Journal of Entomology and Zoology Studies
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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Journal of Entomology and Zoology Studies
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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Journal of Entomology and Zoology Studies
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
Table 2: Adulticidal activity of Nicotiana tabacum leaf extracts against Cylas formicarius at 48 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 0.33 ±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
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.
Table 3: Adulticidal activity of Nicotiana tabacum leaf extracts against Cylas formicarius at 72 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 0.67 ±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
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.
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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Journal of Entomology and Zoology Studies
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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Journal of Entomology and Zoology Studies
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