1. Toxic Effects of some Pungent Smelling Seed Extracts and Powders on Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) Infesting Stored Maize Grains
Toxic Effects of some Pungent Smelling Seed Extracts and
Powders on Sitophilus zeamais Motschulsky (Coleoptera:
Curculionidae) Infesting Stored Maize Grains
1Obembe, Olusola Michael, *2Ojo Durojaye Olanrewaju, 3Odetoye Adefunke Adedayo
1Department of Plant Science and Biotechnology, Plant Resources Management Programme, Faculty of Science, Ekiti
State University P.M.B 5363, Ado-Ekiti, Nigeria
2Department of Zoology and Environmental Biology, Faculty of Science, Ekiti State University, P. M. B. 5363, Ado Ekiti,
Nigeria.
3Department of Crop Science and Horticulture, Faculty of Agriculture, Federal University Oye, Nigeria.
Sitophilus zeamais is a notorious field-to-store pest of maize in the Tropic. The use of chemical
insecticides, regardless of its adverse effects has been the major means of managing this pest.
In this study, bio-insecticides of plant origin was used to control maize weevil in the store. The
dry fruits of Capsicum frutescens, Piper guineense and Aframomum melegueta were extracted
with ethanol, using Soxhlet apparatus. The extracts and powders were evaluated on S. zeamais
Motschulsky for mortality, oviposition and adult emergence. The long term storage of the treated
maize was also investigated. The results obtained shows that all extracts and powders from C.
frutescens and P. guineense caused 100 % mortality by day 12 of exposure with all extract
concentrations and doses of powder applied. Powders of A. melegueta was able to achieve 100
% mortality only by day 12 of exposure. The extracts also suppressed oviposition and subsequent
adult emergence. Extracts and powders of A. melegueta and P. guineense completely prevented
infestation and hence damage of the treated maize grains for a period of three months. The result
obtained suggests that extracts and powders of the test plants most especially that of P.
guineense and C. frutescens can be utilized in protecting stored maize grains from infestation by
S. zeamais.
Key words: Sitophilus zeamais, Capsicum frutescens, Piper guineense, Aframomum melegueta, bioinsecticides,
oviposition, mortality and infestation
INTRODUCTION
Maize, Zea mays L. is the most important cereal crop in
Africa and one of the world’s three most important cereal
crops after rice and wheat (Asawalam and Hassanali,
2006). It is the cheapest form of dietary carbohydrate
(Rouanet, 1992) for human and livestock consumption in
Nigeria. It also provides raw ingredients for industries and
supports worldwide business worth 40 million dollars
annually. About 60-80 % of maize produced in Nigeria is
stores at the farm level in order to enhance food supply as
well as providing income for farmers (Golod et al., 1999).
However, the storage of maize has been hampered by
insect pest.
Maize weevil, Sitophilus zeamais (Motsch.) is a major
serious cosmopolitan pest of stored grains, most
especially maize, in the tropic and the sub-tropic region of
the world (Throne, 1994; Adedire et al., 2011). S. zeamais
is a serious primary pest of maize but it is found
secondarily attacking other crops such as rice, guinea
corn, yam products, groundnut, cowpea, millet, cassava
*Corresponding Author: Ojo Durojaye Olanrewaju,
Department of Zoology and Environmental Biology,
Faculty of Science, Ekiti State University, P. M. B. 5363,
Ado Ekiti, Nigeria. Email: entojo1@gmail.com
Research Article
Vol. 6(1), pp. 142-148, February, 2020. © www.premierpublishers.org. ISSN: 2326-7262
International Journal of Entomology and Nematology

2. Toxic Effects of some Pungent Smelling Seed Extracts and Powders on Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) Infesting Stored Maize Grains
Obembe et al. 143
flavour, cocoyam and beniseed in Nigeria (Nwanna 1993;
NRI, 1996). Adult weevils and larvae feed on wholesome
grains and reduce them to powdery form. The female
weevil lays its eggs singly in holes made in the grain with
it mouthparts and plug it with waxy material. The eggs
hatch into larva which feed exclusively on the grain. Each
larva develops within the grain. Matured larvae pupate and
develop into adult inside the grain (Ofuya and Lale, 2001).
The control of insect pest has been achieved in the past
through the use of synthetic chemical insecticides and this
has constituted a lot of problems such as mammalian
toxicity, high level of persistence in the environment,
workers safety, ozone layer depletion potential, insect
resistance and environmental pollution, leading to health
hazards (Adedire and Ajayi, 1996). Considering these
shortcomings of chemical insecticides, attention is
currently being focused on the use of botanicals for crop
protection because they are ecologically friendly,
biodegradable, have low mammalian toxicity (Obembe
and Ojo, 2018; Obembe and Kayode, 2018).
Several compounds of medicinal plant origin have been
discovered to exert various physiological and behavioural
activities on stored product insects (Echendu 1991;
Okosun and Adedire, 2010). Lajide et al. (1998) reported
that pulverised seeds of Uvaria afzelli, Eugenia aromatica
and bark of Erythrophleum guineense were highly toxic to
maize weevil when used for coating maize grains. In this
study, the effectiveness of three pungent smelling seeds
namely, Capsicum frutescens, Piper guineense and
Afromomun melegueta seed extracts were evaluated for
the protection of maize grains against infestation by S.
zeamais during storage.
MATERIALS AND METHODS
The study was conducted in Plant Science and
Biotechnology Department Laboratory, Ekiti State
University, Ado Ekiti, Nigeria.
Insect culture
The initial culture of Sitophilus zeamais used for the
experiment was obtained from a Mojere market, Ado Ekiti,
Ekiti State, Nigeria, along with infested maize grains. The
insects were cultured at the temperature 28 ± 2oC and 75±
5% relative humidity inside plastic container covered with
muslin cloth to disallow the escape of the insect as well
prevent the entry of intruding insects. The culture was
maintained by replacing the devoured seeds with new un-
infested seeds.
Collection and preparation of plant materials
Dry fruits of Capsicum frutescens, Piper guineense and
Aframomun melegueta where purchased from Mojere
market, Ado-Ekiti, Nigeria. The seeds were removed from
the fruits and air-dried in the laboratory for a period of
seven days to reduce the moisture content in order to
prevent moldiness. The air-dried seeds were pulverized
into fine powders using an electric blender. The powders
were sieved and passed through 1 mm2 mesh. Thereafter,
the powders were measured separately into beakers and
packed into thimbles and extracted with 250 mL of ethanol
in a Soxhlet apparatus at 60oC. The extract was
concentrated by removing the solvent using rotary
evaporator. The resulting extract was further concentrated
by air-drying to remove traces of the solvent. The extracts
were immediately used for the experiment.
Effect of Capsicum frutescens, Piper guineense and
Aframomun melegueta seed powders on mortality of
Sitophilus zeamais
Twenty grams of clean and dis-infested maize grain was
weighed into conical flask and seed powders weighing 0.3,
0.6, 0.9 and 1.2 g were added to the maize grains in 100
mL volume conical flasks. The maize grains and powders
were thoroughly mixed together to enhance uniform
spreading of the powders. Untreated maize grain was also
set up to serve as the control experiment. Twenty teneral
adults of S. zeamais were introduced into each of the
conical flasks and covered with muslin cloth held tightly in
place with rubber band. Each of the treated and untreated
control was replicated four times and laid in Complete
Randomized Design (CRD). Beetle mortality was
observed at 3 days interval for a period of 12 days. After
every 3 day, the number of dead beetles were counted and
recorded. The beetles were confirmed dead when there
was no response to probing on the abdomen with a sharp
pin.
Effect of Capsicum frutescens, Piper guineense and
Aframomum melegueta seed extracts on mortality of
S. zeamais.
Twenty grams of clean and dis-infested maize grains was
weighed into 100 mL volume conical flask and treated with
0.5, 1.0, 1.5 and 2.0 % v/w seed extracts. Untreated grain
was set up to serve as the control experiment. The maize
grains and the extracts were thoroughly mixed with glass
rod to enhance uniform coating of the extracts on the
grains. Thereafter, the treated grains were air-dried for a
period of 1 h, after which 20 teneral adult S. zeamais (0-7
days old) were introduced into the Petri dishes containing
the treated and the control experiment. Four replicates
were prepared for each treatment and the control and laid
in a Complete Randomized Design. The numbers of dead
beetles were counted and recorded at 3 days interval for a
period of 12 days. The beetles were confirmed dead when
there was no response to probing on the abdomen with a
sharp pin
Effect of Capsicum frutescens, Piper guineense and
Aframomum melegueta seed powder on oviposition
and adult emergence of S. zeamais.
Twenty grams of dis-infested maize grains were measured
into each of 100 mL volume conical flask and Capsicum

3. Toxic Effects of some Pungent Smelling Seed Extracts and Powders on Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) Infesting Stored Maize Grains
Int. J. Entomol. Nematol. 144
frutescens, Piper guineense and Aframomum melegueta
powders each weighing 0.3, 0.6, 0.9 and 1.2 g were added
to the maize grains in each of the conical flask. The powder
and the maize grains were thoroughly mixed together to
enhance uniform spreading of the extracts on the maize
grains. Untreated maize grain was also set up to serve as
the control experiment. Two pairs of newly emerged
copulating adult S. zeamais were introduced into each
conical flask and covered with muslin cloth held in place
with rubber band. Each treated and untreated control was
replicated four times and laid in Complete Randomized
Design (CRD). The set up was left in the laboratory for 12
days after which the insects were removed and the
numbers of egg plugs were identified and counted after
staining with acid fuchsin dye solution (Frankenfeld, 1948).
Thereafter, the experimental set-up was kept undisturbed
in the wooden cage till the emergence of adults. The
number of adults that emerged were counted and recorded
Effect of Capsicum frutescens, Piper guineense and
Aframomum melegueta seed extracts on oviposition
and adult emergence of S. zeamais
Twenty grams of clean and un-infested wholesome maize
grains was weighed into 100 mL volume conical flask and
treated with 0.5, 1.0, 1.5 and 2.0 % v/w of the oil. Untreated
maize grains serve as the control experiment. The maize
grains and the oil were thoroughly mixed with glass rod to
facilitate uniform coating of the oil on the seeds.
Thereafter, the treated grains were air-dried for a period of
1 h, after which 2 pairs of newly hatched copulating adult
S. zeamais (0-7 days old) were introduced into the Petri
dish containing the treated and the control experiment.
Four replicates were prepared for each treatment and the
controls and laid in a Complete Randomized Design. The
experimental set-up was left in a wooden cage in the
laboratory for 12 days after which the insects were
removed and the numbers of egg plugs were identified and
counted after staining with acid fuchsin dye solution
(Frankenfeld, 1948) as discussed above. Thereafter, the
experimental set-up was kept undisturbed in a wooden
cage till the emergence of adults. The number of adults
that emerged were counted and recorded
Effect of Capsicum frutescens, Piper guineense and
Aframomum melegueta seed powders on grain
damage
Cotyledon powders of Capsicum frutescens, Piper
guineense and Aframomum melegueta at the rate of 0.3,
0.6, 0.9 and 1.2 g was added to 50 g clean and dis-infested
maize grains in a transparent plastic container. The
container was thoroughly shaken to enhance the spread of
the powders on the maize grains. Thereafter, 20 adult
beetles were introduced into the container. A control
without any powder was included in the set-up. Each
treated and control was replicated four times. Each plastic
container was covered with muslin cloth held tightly in
place with rubber band to prevent the escape of insects
and to facilitate adequate ventilation. The experimental
set-ups were kept in a wooden cage in the laboratory for
90 days. After 90 days the seeds were assessed for seed
damage and weight loss. Percentage seed damage was
determined using the formula below:
% Seed damage =
Number of seeds damaged
Total number of seeds
× 100
1
Data analysis
All data obtained were subjected to analysis of variance
and where significant differences existed, means were
separated using Tukey’s test
RESULTS
Effect of seed powders of the test plants on mortality
of S. zeamais
The effects of seed powders of the test plants on mortality
of S. zeamais are presented in Table 1. All the seed
powders effectively caused mortality which is significantly
different from that of the control. Mortality of S. zeamais
increased gradually with time of exposure and the amount
of dosages used. Seed powders of C. frutescens caused
100 % mortality when treated with 0.3, 0.6, 0.9 and 1.2 g
by day 12 of exposure while all dosages of P. guineense
used caused 100 % mortality by days 9 and 12 of
exposure. The least effective seed powder is that of A.
melegueta which only caused 100 % mortality when
treated with 1.2 g seed powder.
Effect of seed extracts of the test plants on mortality
of S. zeamais
The extracts used caused high mortality of S. zeamais.
Weevil mortality also increased with increased in time of
exposure and concentration of extracts used. Weevils
mortality in the exrract-treated grains was significantly (p <
0.05) different from weevil mortality in untreated grains
(Table 2).
Maize grains treated with 0.5, 1.0, 1.5 and 2.0 % of C.
frutescens and P. guineense seed extracts caused 100 %
mortality of S. zeamais by days 6, 9 and 12 after treatment.
C. frutescens seed extract caused 100 % mortality by day
3 on exposure to 2.0 % seed extract while that of P.
guineense was able to cause 100 % mortality when
exposed to 1.0 and 1.5 % seed extracts by day 3 of
exposure. Seed extracts of A. melegueta was able to effect
69.25, 78.15, 88.25 and 100 % mortality when treated with
0.5, 1.0, 1.5 and 2.0 % seed extracts respectively.
Effect of seed powders of test plants on oviposition
and adult emergence of by S. zeamais
The seed powders used in this study drastically reduced
the number of eggs laid by S. zeamais (Table 3).

4. Toxic Effects of some Pungent Smelling Seed Extracts and Powders on Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) Infesting Stored Maize Grains
Obembe et al. 145
Oviposition was significantly lowered (P< 0.05) in powder-
treated grains than the control grains. Oviposition and
adult emergence decreased with increased in powder
dosages of all the seed powders used. No egg was laid in
maize grains treated with 1.2 g of C. frutescens and that of
9.0 and 1.2 g of P. guineense. No adult emerged in maize
grains treated with 9.0 and 1.2 g seed powders of C.
frutescens and that of 6.0, 9.0 and 1.2 g of P. guineense
Effect of seed extracts of the test plants on oviposition
and adult emergence of S. zeamais.
All extracts of the test plants caused reduction in the
number of eggs laid by the weevils (Table 4). Oviposition
by weevils was significantly lowered (P<0.05) in extract-
treated grains than the control grains. The number of eggs
laid and number of adults that emerged decreased with
increased in extracts concentration. Oviposition was totally
prevented in grains treated with 1.5 and 2.0 % extracts of
C. frutescens and P. guineense. There was no adult
emergence in grains exposed to 0.5, 1.0, 1.5 and 2.0 %
seed extracts of C. frutescens and P. guineense.
Oviposition and adult emergence were only prevented in
maize grains exposed to 2.0 % extracts of A. melegueta.
Protection of maize grains with seed powders of the
test plants
Seed powders of C. frutescens and P. guineense
completely prevented grain infestation and subsequent
grain damage and hence weight loss for a period of 90
days (Table 5). There was 26.94 and 10.25 % grain
damage and weight loss recorded respectively in maize
grains treated with seed powders of A melegueta
Protection of maize grains with seed extracts of the
test plants
Seed extracts of C. frutescens and P. guineense
completely prevented infestation and consequent damage
and weight loss by S zeamais for a period of 90 days
(Table 6). Seed extracts of A. melegueta drastically
reduced infestation, grain damage and weight loss for a
period of 90 days.
Table 1: Mean percentage mortality of S. zeamais treated with powders of Capsicum frutescens, Piper guineense and
Aframomum melegueta
Tested plants Dosage (g) Day 3 Day 6 Day 9 Day 12
C. frutescens 0.3 57.20±2.50cd 76.15±1.30b 84.25±3.25b 100.00±0.00a
0.6 68.50±4.20c 84.22±2.14b 95.15±1.00a 100.00±0.00a
0.9 77.15±2.08b 88.45±0.25b 100.00±0.00a 100.00±0.00a
1.2 82.50±3.50a 100.00±0.00a 100.00±0.00a 100.00±0.00a
A. melegueta 0.3 26.25±2.25e 34.15±2.73de 48.15±2.08d 57.20±2.13d
0.6 28.75±3.25e 45.38±7.78d 54.22±7.78d 68.15±7.40c
0.9
1.2
33.20±1.77d
45.25±2.08d
54.35±3.96cd
62.15±3.06c
68.15±2.22c
77.35±3.33c
70.50±2.34c
80.50±2.13b
P. guineense 0.3 62.10±2.75c 92.25±3.11b 100.00±0.00a 100.00±0.00a
0.6 73.75±8.29b 100.00±0.00a 100.00±0.00a 100.00±0.00a
0.9
1.2
78.25±1.23b
100.00±0.00a
100.00±0.00a
100.00±0.00a
100.00±0.00a
100.00±0.00a
100.00±0.00a
100.00±0.00a
Control 0.0 0.00±0.00f 0.00±0.00e 0.00±0.00e 0.00±0.00e
Each value is the mean ± standard error of four replicates. Means in the same column followed by the same letter(s) are
not significantly different at p ≥ 0.05 by Tukey’s test
Table 2: Mean percentage mortality of S. zeamais treated with extracts of Capsicum frutescens, Piper guineense and
Aframomum melegueta
Tested plants Conc % (v/w) Day 3 Day 6 Day 9 Day 12
C. frutescens 0.5 88.25±3.33b 100.00±0.00a 100.00±0.00a 100.00±0.00a
1.0 92.15±2.22ab 100.00±0.00a 100.00±0.00a 100.00±0.00a
1.5 98.30±1.33a 100.00±0.00a 100.00±0.00a 100.00±0.00a
2.0 100.00±0.00a 100.00±0.00a 100.00±0.00a 100.00±0.00a
A. melegueta 0.5 30.15±2.25cd 38.25±3.30bc 58.25±3.04c 69.25±1.34cd
1.0 38.25±1.25c 54.25±1.20bc 65.25±2.20c 78.15±3.40c
1.5 48.75±2.22c 62.35±1.22b 72.15±3.23bc 88.25±1.50b
2.0 60.25±2.08b 75.35±3.06b 88.15±4.08b 100.00±0.00a
P. guineense 0.5 92.25±1.77ab 100.00±0.00a 100.00±0.00a 100.00±0.00a
1.0 97.50±2.20a 100.00±0.00a 100.00±0.00a 100.00±0.00a
1.5 100.00±0.00a 100.00±0.00a 100.00±0.00a 100.00±0.00a
2.0 100.00±0.00a 100.00±0.00a 100.00±0.00a 100.00±0.00a
Control 0.0 0.00±0.00d 0.00±0.00e 0.00±0.00e 0.00±0.00e
Each value is the mean ± standard error of four replicates. Means in the same column followed by the same letter(s) are
not significantly different at p ≥ 0.05 by Tukey’s test

5. Toxic Effects of some Pungent Smelling Seed Extracts and Powders on Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) Infesting Stored Maize Grains
Int. J. Entomol. Nematol. 146
Table 3: Mean oviposition count and adult emergence of
S. zeamais treated with powders of Capsicum frutescens,
Piper guineense and Aframomum melegueta
Tested
plants
Conc. %
(v/w)
No of eggs
laid
Mean No. of
adult emerged
C. frutescens 3.0 8.25±0.75cd 26.75±2.49b
6.0 5.50±1.55d 12.20±2.24d
9.0 3.15±2.20d 0.00±0.00e
1.2 0.00±0.00e 0.00±0.00e
A. melequeta 3.0 22.25±0.85b 32.15±2.13b
6.0 18.38±2.30b 16.20±1.15c
9.0 16.12±3.22c 10.15±1.22d
1.2 12.20±1.15c 0.00±0.00e
P. guineense 3.0 7.20±2.25cd 18.30±2.20c
6.0 3.25±1.22d 0.00±0.00e
9.0 0.00±0.00e 0.00±0.00e
1.2 0.00±0.00e 0.00±0.00e
Control 0.0 30.25±0.75a 56.15±2.75a
Each value is the mean ± standard error of four replicates.
Means in the same column followed by the same letter(s)
are not significantly different at p ≥ 0.05 by Tukey’s test.
Table 4: Mean oviposition count and adult emergence of
S. zeamais treated with exracts of Capsicum frutescens,
Piper guineense and Aframomum melegueta
Tested plants Conc. %
(v/w)
No of eggs laid Mean No. of
adult emerged
C. frutescens 0.5 6.35±1.40bc 0.00±0.00e
1.0 3.20±3.12c 0.00±0.00e
1.5 0.00±0.00d 0.00±0.00e
2.0 0.00±0.00d 0.00±0.00e
A. melequeta 0.5 10.75±0.85b 38.15±2.20b
1.0 7.25±1.25bc 26.25±1.13c
1.5 4.35±1.32c 12.75±1.22d
2.0 0.00±0.00d 0.00±0.00e
P. guineense 0.5 4.25±2.20c 0.0.±0.00e
1.0 2.35±1.10cd 0.00±0.00e
1.5 0.00±0.00d. 0.00±0.00e
2.0 0.00±0.00d. 0.00±0.00e
Control 0.0 30.25±0.75a 56.15±2.75a
Each value is the mean ± standard error of four replicates.
Means in the same column followed by the same letter(s)
are not significantly different at p ≥ 0.05 by Tukey’s test.
Table 5: Effect of Capsicum frutescens, Piper guineense and Aframomum melegueta seed powders on long term storage
of maize grains.
Name of Plant No. of seed Mean of damaged seed Mean % grain Mean % weight loss
C. frutescens 168.50 0.00±0.00 0.00±0.00c 0.00±0.00c
A. Melegueta 167.75 45.20±1.25 26.94±1.25b 10.25±1.22b
P. guineense 169.25 0.00±0.00 0.00±0.00c 0.00±0.00c
Control (Untreated) 168.50 150.50±2.15 89.32±1.72a 42.10±2.23a
Each value is the mean of 4 replicates. Mean in each column followed by the same alphabet(s) are not significantly
different (p ≥ 0.05) by Tukey’s test.
Table 6: Effect of Capsicum frutescens, Piper guineense and Aframomum melegueta seed extracts on long term storage
of maize grains.
Name of Plant No. of seed Mean of damaged seed Mean % grain Mean % weight loss
C. frutescens 170.20 0.00±0.00 0.00±0.00c 0.00±0.00c
A. Melegueta 168.50 33.25±2.25 13.80±1.25b 12.35±2.20b
P. guineense 169.25 0.00±0.00 0.00±0.00c 0.00±0.00c
Control (Untreated) 170.20 152.20±3.15 89.32±1.55a 40.20±3.33a
Each value is the mean of 4 replicates. Mean in each column followed by the same alphabet(s) are not significantly
different (p ≥ 0.05) by Tukey’s test
DISCUSSION
The results obtained from this research showed that seed
extracts and powders of Capsicum frutescens, Piper
guineense and Aframomum melegueta were found to be
effective in the control of maize weevils, S. zeamais.
Extracts and powders of C. frutescens and P. guineense
were found to be very effective in the control of Sitophilus
zeamais as revealed by their potency on the insect in term
of their ability to cause 100% mortality right from the sixth
to twelfth day of exposure to the powders and extracts and
hence totally preventing oviposition and adult emergence.
The powders also prevented grain damage and weight
loss. The observed mortality can be ascribed to the
pungency of the extract and powder of C. frutescens and
P. guineense. It can also be due to their pepperish nature.
Some interesting developments have been made in the
use of plant extracts and powders in the control of weevils.
The observation in the present study tallies with the
findings of Cobley and Steele, 1976; Ivbijaro and Agbaje,
1986; Lale, 1992: Lajide et al., 1998; who observed that
Powders and extracts of C. frutescens, P. guineense and
Pipper umbellatum adversely affected the biology of maize
weevil and also cause high adult mortality. Also, Lale, 1992
reported that Aligator pepper, A. melegueta seed powder
and extract have been found effective in controlling adult
S. zeamais.
Oviposition and adult emergence by S. zeamais female
were totally inhibited in maize grains treated with C.
frutescens and P. guineense powder and extract as
against their oviposition in the untreated maize grains.
Boeke et al., 2001 has also reported that plant extracts
induce reduction or complete inhibition of oviposition by

6. Toxic Effects of some Pungent Smelling Seed Extracts and Powders on Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) Infesting Stored Maize Grains
Obembe et al. 147
female coleopteran pests and also effected the mortality of
the developmental stages. The ability of the powder and
extract to cause 100 % mortality in the present study may
also be due to respiratory impairment, which must have
probably affected the process of metabolism and hence
the functioning of the body system of the beetle
(Onolemhemhem and Oigiangbe, 1991). The significant
reduction in adult emergence was as a result of the
efficacy of the powder and extract. Botanical insecticides
weaken adult weevil suppressing or totally preventing
oviposition and causing reduction in hatchability of the
eggs to larvae and final metamorphosis to adults. The
effectiveness of different non-synthetic chemical products
to various storage insect pests of stored products have
been reported by several authors (Huang et al., 2000; Oni
and Ileke 2008; Adedire et al., 2011). It was also reported
that botanical based products may act as fumigant,
repellent, stomach poison and physical barrier against
various insects (Adedire et al., 2011). Higher concentration
of the extracts and higher dosage of the powder could be
more effective in insect control since it is expected to
contain more active ingredients
The result obtained from this study confirmed that extracts
and powders of Piper guineense and Capsicum frutescens
were very effective in controlling the population of S.
zeamais.
REFERENCES
Adedire CO, and Ajayi TS. (1996). Assessment of the
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7. Toxic Effects of some Pungent Smelling Seed Extracts and Powders on Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) Infesting Stored Maize Grains
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Accepted 21 November 2019
Citation: Obembe OM, Olanrewaju OD, Adedayo OA
(2020). Toxic Effects of some Pungent Smelling Seed
Extracts and Powders on Sitophilus zeamais Motschulsky
(Coleoptera: Curculionidae) Infesting Stored Maize
Grains. International Journal of Entomology and
Nematology, 6(1): 142-148.
Copyright: © 2020 Obembe et al. This is an open-access
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