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Ife Journal of Science vol. 16, no. 3 (2014)
INFLUENCE OF FOUR CEREAL FLOURS ON THE GROWTH OF TRIBOLIUM
CASTANEUM HERBST (COLEOPTERA: TENEBRIONIDAE)
*Kayode O. Y., Adedire C. O. and Akinkurolere R. O.
Department of Biology, Food Storage Technology Programme, Federal University of Technology,
Akure, Ondo State, Nigeria
Corresponding Author: yemmyfk@gmail.com
(Received: 8th August, 2014; Accepted: 6th October, 2014)
The influence of four cereals namely, flours of wheat (Triticum aestivum L.), millet (Pennisetum glaucum L.),
sorghum (Sorghum bicolor (L.)Moench) and maize (Zea mays L.)on the growth and development of T. castaneum was
investigated at ambient tropical laboratory conditions of 30±3˚C and relative humidity of 75±5%. The anti-
nutrients, mineral profile and proximate compositions of the four flour types and their effects on the
developmental activity of the flour beetle were studied. Results showed that the moisture content of the cereal
flours ranged from 7.64% in wheat to 9.24% in maize, while protein content ranged from 10.91% in millet to
17.23% in wheat flour and the ash content in the flours ranged from 1.05% in maize to 2.59% in millet. However,
the four cereal flours had sufficient nutrients to support the growth of T. castaneum. Millet flour had the highest
number of larvae (435.50±0.85) at 56-day post-infestation thus depicting millet flour as the most preferred flour
type for oviposition and egg incubation; while the lowest (286.25±0.41) number of larvae was obtained in maize
flour and it was significantly lower (p≤0.05) than the number of emerging larvae in other flour types. The
highest number of pupae was recorded in millet (387.50±0.65) and lowest in maize flour (312.25±0.65). The
highest number of emergent adult Triboliumb was recorded in millet (357.00±0.41) and lowest in maize
(268.25±0.65). Host preference (choice and no-choice) studies revealed millet flour as the most preferred food
and maize flour as the least preferred. Based on the flour colour, anti-nutrient composition and population of
the immature forms of the flour beetle, maize flour was the most unsuitable food source, while millet flour was
the most susceptible to T. castaneum.
Key words: Anti-Nutrients, Proximate Composition, Flour Colour, Cereal Flours, Rust-Red Flour Beetle,
Tribolium castaneum.
ABSTRACT
505
INTRODUCTION
The rust-red flour beetle, Tribolium castaneum
Herbst, is one of the most widespread and
destructive pests of stored products, feeding on
different stored grain and grain products in the hot
humid tropical regions of the world (Padin et al,
2013).
In Nigeria, the host range of the rust-red flour
beetle includes a wide range of food stuffs such as
milled cereal products like wheat, sorghum, millet,
acha, benniseeds, oil seed cake, cowpea,
groundnuts, dried roots and tubers of yam,
cassava, cocoyam, plantain among others (Hill,
1983; Adedire & Oni, 1995; Lale & Yusuf, 2001;
Odeyemi, 2001; Bulus, 2008).
T. castaneum does not possess the ability to infest
and damage wholesome grains or products but
they reproduce rapidly in milled or damaged grains
and products. Their short life cycle coupled with
low mortality of their immature forms account
for the high reproductive success of this species
(Howe, 1962). The larva is the most destructive
stage of the beetle and its intensive feeding activity
results in most serious damage to stored produce.
The beetles contaminate the stored products with
their excreta, exuviates, body odour and their
cadavers thus reducing the palatability, rheological
properties and market value of stored flours.
Recently, there is a huge decline in the use of
synthetic insecticides in agriculture particularly in
stored products protection in developing nations
primarily because of partial or complete
withdrawal of subsidies by governments,
sustained propaganda on organic agriculture and
undesirable health implications of the use of
chemical pesticides and its effect on the
environment by environmentalists and other
concerned non-governmental organizations
(Akinkurolere et al, 2011).
506
The application of resistant species and varieties
has been the major focus of many researchers in
recent times. According to Lale and Yusuf (2001),
many research efforts appeared focused on high
value crops such as maize, cowpea, rice,
groundnuts etc. Food commodities are known to
influence post-embryonic development in the
Indian meal moth, Plodiainter punctella (Hubner). It
is fairly well known that the life cycle of insects is
greatly influenced by environmental factors
notably the quality of food (Bouayad et al., 2008).
This has been demonstrated in storage beetles and
moths (Savov, 1973; Locatelli & Limonta, 1998;
Bulus, 2008).
Generally, four important mechanisms namely
antibiosis, antixenosis, tolerance and escape are
responsible for insect pest resistance. According
to Keneni et al. (2011), escape and tolerance are
resistance mechanisms that are only relevant to
field crop infestations while antibiosis and
antixenosis are applicable to storage insect pests. A
number of physiological and/or biochemical
mechanisms may protect stored crops from insect
pest depredation. In legumes for example, an array
of direct and indirect defenses such as
morphological barriers, secondary metabolites
and anti-nutrients confer resistance on legume
seeds (Edwards &Singh, 2006).
Wheat, millet, sorghum and maize flours are highly
consumed in many parts of sub Saharan Africa.
They are a common staple food in developing
countries including Nigeria. Their deterioration in
storage due to the infestation by T. castaneum and
other microorganisms leads to losses which in turn
has adverse effects on the economy of the nation
and health of the people. It is therefore necessary
that such losses be investigated so as to provide
adequate information that will guarantee food
security in developing countries.
Hence, this study was conducted to determine the
influence of four flours namely, wheat, millet,
sorghum and maize on infestation and
development of T. castaneum using proximate
composition, mineral profile, anti-nutrients and
beetle growth as indices.
MATERIALS AND METHODS
Source of Food Media and Insects
Four cereals namely wheat, sorghum, millet and
maize grains, used for the experiments were
purchased at the Akure main market (“Oja Oba”
Akure), Ondo State and T. castaneum adult insects
used were obtained from the Entomology
Research Laboratory, Department of Biology,
Federal University of Technology, Akure, Nigeria.
Preparation of the Food Media
The grains of maize, sorghum, wheat and millet
used in this study were winnowed and thoroughly
sorted to remove stones and other foreign
materials. The seeds were then pulverized into
fine powder in a “Muchang blender model No.
9FZ-300” until finely divided powder was
obtained. The flours were held in covered plastic
containers at ambient tropical laboratory
conditions of 30±2˚C and relative humidity of
75±5%. The colours of the prepared flours were
also noted.
Sex Determination of Tribolium castaneum
To determine the sex of the rust-red flour beetle,
T. castaneum, the pupal stage of the insect was
placed on a slide and viewed under a binocular
microscope for the sex characteristics. The sexes
were confirmed by observing the genital papillae
on the ventral side of the distal abdominal
segment. The female pupae possess well
developed, protruding genital papillae while the
males possess reduced genital papillae compared
to females (Parthasarathyet al., 2008).
Insect Rearing
T. castaneum adults were cultured in wheat flour
under tropical laboratory conditions of 30±2˚C
and relative humidity of 75±5%. Each wheat
flour was measured into separate containers
(250g/container) and 30 adult beetles (♀:♂ = 1:1)
were introduced into the medium and covered to
prevent possible escape of the beetles. The
containers were then kept in the culturing
chamber (cage) made of wire gauze to prevent
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
507
cross infestation. After 7 days, the adult beetles
were removed. The culture was observed weekly
until teneral adults needed for the subsequent
experiments started emerging.
Determination of the Proximate Composition
of the Flour Types.
To determine the growth factors in the flours, the
nutrient contents such as crude protein, moisture,
lipid, ash and crude fibre and carbohydrate were
assayed using the official methods of the
Association of Analytical Chemists (AOAC,
1990). These analyses were carried out on wheat,
sorghum, millet and maize flours, respectively.
Determination of the Mineral Profile of the
Four Flour Types
The mineral analyses were carried out on all the
samples as follows: One gram (1g) of each sample
was ashed in a muffle furnace at 550°C. The ashed
sample and dishes were removed and transferred
into the desiccator to cool after which the samples
were dissolved with 1ml of concentrated HNO .
3
Little distilled water was added and filtered into a
clean small plastic bottle using Whatman No. 43
filter paper. Distilled water was later used to dilute
the solution up to 50ml. Atomic absorption
spectrophotometer Buck 210 Model 200 was used
in determining the concentration of the metals:
Copper (Cu), Iron (Fe), Manganese (Mn), Lead
(Pb), Magnesium (Mg), Calcium (Ca) and Zinc
(Zn) while sodium (Na) and Potassium (K) were
determined by flame photometry.
Anti-Nutrient Analyses of the Flour Media
Anti-nutrient contents were estimated by the
bioassay procedures of AOAC (1990) as modified
by various authors cited in specific assays. The
modified procedure of Day & Underwood (1986)
was used to determine the oxalate content. The
phytate and saponincontent of the flour types
were assayed by protocols described by Obadoni
& Ochuko (2001).
The tannin contents were determined using the
Folin Denis reagent as described by Makkar et al.,
(1993). A standard calibration curve was prepared
and the absorbance (A) against concentration of
tannins at 725nm was estimated.
Effect of the Food Type on the Growth of
Tribolium castaneum
To determine the effect of food type on the
growth of the rust-red flour beetle, an experiment
was carried out under ambient tropical laboratory
conditions of 30±2˚C and 75±5% r.h. Two
copulating pair of adult T. castaneum were
introduced into each of the four replicates of 20g
of each of the different food media (i.e wheat,
sorghum, maize and millet flours) measured into
small plastic containers with the lid perforated
and sealed with a muslin cloth to prevent the
escape of the insects. The containers were
thereafter kept in the culturing chamber (cage)
made of wire gauze to prevent cross infestation.
The adult beetles were removed after 7 days by
2
sieving the flour with a sieve of 0.5mm mesh size.
th
The experiment was observed on the 14 day after
the introduction of the insects and subsequently
th
on weekly basis until the 56 day for the
emergence of larvae, pupae and adults. The flour
media were sieved to facilitate the separation of
the various life-forms (larva, pupa, adult). The
population growth was checked by counting the
number of larvae, pupa and adult insects in each
replicate of the food media.
Host Preference Studies in Tribolium castaneum:
Choice and No-Choice Tests
Choice Test
This procedure investigates the feeding
preference of T. castaneum on each of the flour
media namely; wheat, millet, sorghum and maize.
This experiment was carried out in 4 replicates.
Plastic Petri dishes were divided into four sections
with paraffin wax after which 5 g each of the
flours were introduced into the individual
sections and labelled. Ten adult males and ten
females of T. castaneum were introduced into the
centre of each Petri dish and covered. The Petri
dishes were sealed off with a paper tape to prevent
the insects from escaping and they were thereafter
kept in an insect cage. The insects were allowed to
copulate and removed after 7 days. On the
fourteenth day, the flour in each section was
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
508
carefully removed and sieved using 0.05 mm mesh
size. The filtrate was then observed under a
monocular light microscope to view the number
of larva in each section.
No-Choice Test
This test was aimed at investigating the
development of T. castaneum in four different flour
media. This experiment was carried out in 4
replicates. Fine flour was obtained from the four
cereal grains used in this experiment. Twenty
grams (20 g) of each of the flours was measured
into separate Petri-dishes. Ten copulating pairs of
adult T. castaneum beetles were introduced into the
plastic Petri-dishes which then were covered and
sealed with paper tape. Other protocols and
observations for larval emergence were as
described in 'choice test' above.
Statistical Analysis
Data obtained from the proximate analysis,
mineral profile and anti-nutrient profile of the
four cereal flours tested and the biological activity
of T. castaneum were subjected to one-way Analysis
of Variance (ANOVA) and where significant
differences existed, treatment means were
compared at 0.05 significant levels using New
Duncan's multiple range test (Zar, 1984).
Furthermore, the aforementioned data were also
subjected to correlation-regression analysis using
®
the SPSS 16.0 (2007 version) statistical package to
identify if there was any relationship between the
chemical composition of the cereal flours and the
biological activity of T. castaneum.
RESULTS
Colour of the Prepared Flour Types
Table 1 shows the colour of the cereal flours used
to rear T. castaneumin the course of this study. The
colour of the flours ranged from white in maize
flour to pink in sorghum flour while whole wheat
flour was light brown in appearance and millet
flour was grey in colour.
Proximate Analysis of the Flour Types
The proximate composition of four cereal flours
namely, wheat, maize, millet and sorghum are
presented in Table 2. Moisture content was lowest
in wheat flour (7.64%) and highest in maize flour
(9.24%) followed by sorghum (8.90%) and millet
flours (8.48%) respectively. There was no
significant difference (P³0.05) between the
moisture content of sorghum and millet, but
significant differences existed between the
moisture content of maize and wheat flour.
Wheat flour had the highest protein content
(17.23%) while millet flour had the lowest protein
content (10.91%). Wheat flour was significantly
different (P<0.05) from the other flour types
(maize, millet and sorghum flour). However,
crude protein in maize, millet and sorghum flours
were not significantly different (P>0.05).
Sorghum has the highest fibre content (2.05%),
while maize flour has the lowest (1.12%). There
were significant differences (P<0.05) in the fibre
content in the four flour types except for maize
(1.12%) and wheat flour (1.16%) that were not
significantly different at P=0.05.
Table 1. The Colours of the Four Cereal Flours
Used as Growth Media for Tribolium castaneum
Flour type Colour
Wheat flour Light brown
Millet flour Grey
Maize flour White
Sorghum flour Pink
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
509
Mineral Analysis of Food Media Used as
Growth Media for Tribolium castaneum
The highest amount of calcium was recorded in
sorghum flour (4.79) while the lowest amount of
calcium occurred in millet flour (0.96) (Table 3).
The calcium content of the four flour types were
significantly different at 5% probability level.
Magnesium content was highest in sorghum flour
(15.07) and lowest in millet flour (8.09). The
magnesium contents were different significantly
(P£0.05) in the four growth media.
Wheat flour had the highest potassium content
(57.56) while the lowest potassium content was
recorded in maize flour (36.50). All the four flour
types showed significant differences in potassium
content at P=0.05. Sodium concentration was
highest in sorghum flour (0.57), followed by wheat
flour (0.55), maize flour (0.45) and millet flour
(0.12). There were significant differences in the
sodium content of all the flours at P=0.05.
Manganese was lowest in maize flour (0.12) and
highest in wheat (0.55). The flours were
significantly different P≤0.05 from each other in
terms of manganese content.
The iron (Fe) content in the four flour types was
significantly different at P=0.05. The iron content
was found to be highest in millet flour (0.92),
followed by sorghum flour (0.78), wheat flour
(0.69) and the lowest value was obtained in maize
flour (0.38).
Sorghum flour had the highest amount of copper
(2.15), while the lowest (0.20) was recorded in
millet flour. There was no significant difference
(P³0.05) between millet and wheat flours in terms
Food media Moisture
Fibre
Ash
Protein
Fat content
Carbohydrate
Sorghum
8.90
ab
± 0.36
2.05c ± 0.12
1.65a ± 0.14
11.34a ± 0.26 16.45a ± 1.11 59.61a±1.18
Maize
9.24b ± 0.38
1.12b ± 0.03
1.05a ± 0.10
11.05a ± 0.38 15.11a ± 0.79 62.41a ±1.22
Millet 8.48ab ± 0.38
0.85a ± 0.05
2.59b ± 0.49
10.91a ± 0.55 16.32a ± 1.10 60.85 a±1.46
Wheat 7.64a ± 0.53
1.16b ± 0.02
1.42a ± 0.10
17.23b ± 0.95 13.81a ± 0.82 57.34a±2.28
Table 2: Proximate Composition (%) of Four Flour Types Used as Growth Media for Tribolium
castaneum
Each value is a mean of triplicate samples ± standard error of the mean. Mean values along a column
followed by the same letter(s) are not significantly different at P<0.05 by New Duncan's multiple range
test.
Table 3: Mineral Contents of Four Flour Media Used for Biological Studies of Rust-Red Flour Beetle
Flour type
Concentration of Minerals (ppm)
Ca Mg K Na Mn Fe Cu Zn Pb
Sorghum
Maize
Millet
Wheat
4.79c±0.09 15.07d±0.02 39.38c±0.02 0.57c±0.02 0.15c±0.00 0.78c±0.01 2.15c±0.01 0.43b±0.01 0.06b±0.00
4.13b±0.01 11.55b±0.01 36.35a±0.08 0.45b±0.01 0.07a±0.01 0.38a±0.01 0.36b±0.02 0.35a±0.01 0.02a±0.01
0.96a±0.02 8.09a±0.00 36.80b±0.01 0.37a±0.01 0.12b±0.01 0.92d±0.01 0.20a±0.01 0.36a±0.01 0.06b±0.01
4.67c±0.01 14.13c±0.01 57.56d±0.00 0.55c±0.01 0.55d±0.01 0.69b±0.01 0.23a±0.01 0.40b±0.01 0.05b±0.01
Each value is a mean of four replicate samples ± standard error of the mean. Mean values along a
column followed by the same letter(s) are not significantly different at P<0.05 by New Duncan's
multiple range test.
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
510
of copper content. However, significant
differences existed in the copper content of the
growth media at 5% probability level (Table 3).
Zinc was highest in sorghum flour (0.43) and
lowest in maize flour (0.35). There was no
significant difference (P≥0.05) in the amount of
zinc present in maize and wheat flour. There was
also no significant difference (P≥0.05) between
sorghum and millet flour (Table 3). Table 3 shows
that there was no significant difference (P≥0.05)
in the amount of lead present in sorghum flour,
millet flour and wheat flour. However, the lead
content of maize flour (0.03) was significantly
lower (P≤0.05) than the other flours evaluated.
Table 4: Anti-Nutritional Content (mg/100g) of Four Flour Types Used for Bioassays on T. Castaneum
Food media Oxalate PhytateSaponin Tannin
Sorghum
Maize
Millet
Wheat
0.54
d
±0.00 7.64a±0.53 3.46b±0.07 0.88b±0.05
0.36a±0.00 8.78ab±0.27 2.02a±0.04
0.77b±0.03
0.47c±0.02 9.58b±0.26 3.29b±0.02 0.49a±0.03
0.41b±0.00 13.31c±0.49 3.43b±0.67 0.57a±0.03
Each value is a mean of triplicate samples ± standard error of the mean. Means along a column
followed by the same letter(s) are not significantly different at P<0.05 by New Duncan's multiple range
test.
Antinutrient Contents of the Four Flour
Types Used as Growth Media for Tribolium
castaneum
The antinutrient contents of all the flour types
used in this study is presented in Table 4. The
oxalate, tannin and saponin contents were highest
in sorghum flour while oxalate and saponin were
lowest in maize. Millet (0.49) and sorghum (7.64)
had the lowest tannin and phytate contents.
Wheat flour had the highest phytate content
(13.31) followed by millet flour (9.58) and maize
flour (8.78). Wheat flour showed significant
difference (P£0.05) in the phytate content
compared to the other flour types.
Sorghum flour had the highest oxalate content
(0.54) followed by millet flour (0.47), wheat flour
(0.41) and maize flour (0.36). There were
significant differences (P≤0.05) in the oxalate
contents for all four flour types. Sorghum flour
had the highest saponin content (3.46) while
maize flour had the lowest saponin content (2.02).
There was no significant difference (P≥0.05)
between the saponin content in sorghum, millet
and wheat flours whereas, significant differences
existed between maize flour and the other flours
at P=0.05. Sorghum flour (0.88) has the highest
percentage of tannin compared to the other food
media (Table 3). There was significant difference
(P≤0.05) between the tannin content in wheat
flour and sorghum flour, and no significant
difference (P≥0.05) was obtained between wheat
and millet flours. There was also no significant
difference between the tannin content in
sorghum and maize flour at 5% probability level.
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
511
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
512
The Development of Tribolium castaneum on
Four Flour Types
Larval Development
Larval emergence was first seen in the four flour
th
types on the 14 day (Figure 2). Wheat flour had
th
the highest mean larval count on the 14 day
(38.50±0.65), while maize flour had the lowest
(33.50±0.65). The highest (435.50±4.96) and
lowest (285.25±4.51) mean larval count was
observed in millet flour and maize flour
respectively. There was no significant difference
in the number of larvae in millet flour (36.00) and
th
sorghum flour (36.50) on the 14 day, but the
larval count in wheat and maize flours were
significantly different (P£0.05). There were
significant differences in the number of larvae in
st th
the four growth media on the 21 and 28 day at
P= 0.05 (Figure 2).
Table 5: Food Preference of T. castaneum in Four Flour Types
Food
media
Mean number of larva ± S.E.
Choice test No-choice test
Wheat
Maize
Millet
Sorghum
63.75c ± 0.48 161.00c± 0.71
53.75a ± 0.48 142.25a± 1.10
65.00c ± 0.41 171.75d ± 0.85
57.00b ± 0.41 156.75b ± 0.48
Each value is a mean of four replicate samples±standard error of the mean. Means followed by the
same letter(s) along a column are not significantly different at P<0.05 by Duncan's multiple range
test
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
513
Pupal Development
Figure 3 shows the average number of T. castaneum
pupae that emerged in the four cereal flours. There
was no record of pupal formation in all the food
th
media until the 28 day. Significant differences
existed in the pupal development of the beetle in
th
the four flour types on the 28 day. The highest
number of pupae during the 56-day period was
recorded in millet flour (387.50±3.90); while the
lo we s t wa s re c o r de d i n m a i ze f l o ur
(312.25±3.70).Generally, the four flour types had
significant effect on pupal development.
Adult Emergence
The emergence of adult T. castaneum from infested
flours is presented in Figure 4. No beetle emerged
th th
until the 35 day after infestation. On the 56 day
post-infestation, millet flour had the highest mean
value of adult insects (357.00±2.62) while maize
flour had the lowest mean value (268.25±2.32).
Host Preference Studies
Table 5 shows results of the host preference of T.
castaneum on the four flours investigated. The
number of larvae in wheat flour (63.75) was not
significantly different (P≥0.05) from those found
in millet flour (65.00), but there was a significant
difference (P≤0.05) in the number of larvae
found in maize (53.75) and sorghum flour (57.00).
Correlation between the Development of T.
castaneum and Antinutrient Content in the
Four Flours
From the results of the correlation analysis as
shown in Table 6, sorghum flour had a negative
correlation with the oxalate (-0.73) and phytate
contents (-0.64). There was a negative and non-
significant correlation (-0.32) between saponin
content and sorghum flour. Also, there was a
negative and non-significant relationship (-0.29)
between the tannin content and sorghum flour.
Maize flour had a positive and significant
correlation (0.75) with the oxalate content while
there was a positive but insignificant correlation
(0.37) between maize flour and phytate content.
The saponin content was positively correlated
with maize flour (0.57). Similarly, there was a
positive correlation between tannin content and
maize flour (0.70). Oxalate content and millet
flour were negatively correlated (-0.18). The
phytate content was negatively correlated with
millet four (-0.37). Millet flour and saponin
content were positively correlated (0.13). The
tannin content and millet flour were positively
correlated (0.25) but not significant. There was a
negative correlation (-0.78) between wheat flour
and oxalate content. There was a positive
correlation (-0.77) between wheat flour and
phytate content. Similarly, there was a negative
correlation (-0.95) between saponin and wheat
flour. There was also a negative correlation
between the tannin content (-0.95) and wheat
flour.
DISCUSSION
All the cereal grain flours evaluated in this study
contained ample nutrients to support the growth
and development of the rust-red flour beetle, T.
castaneum. It is also evident from this study that
there are wide variabilities between the different
flours tested with respect to the number of larvae,
pupae and F adults that emerged, level of
1
susceptibility and feeding preference. These taken
together reflect the ability of particular cereal
flour to resist pest attack.
The moisture content of any food is an index of
its water activity and is used as a measure of
stability and the susceptibility to microbial
contamination (Okaraonye and Ikewuchi, 2009).
Makanjuola et al. (2009) reported that the low
moisture content of rice was a likely factor that
conferred susceptibility to rice cultivars in
storage. The moisture contents recorded for all
the flours used in this study were in the safe
moisture range as listed by Hayma (1995).
Carbohydrates serve as a source of energy and
may be converted to fats for storage and to amino
acids (Chapman, 1980). The number of adults
reduced as the development period progressed
because there was no replenishment of the food
media. Chapman (1980) also reported that
Tribolium uses starch, alcohol, trisaccharides,
disaccharides and monosaccharides. Behmer
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
(2006) reported that the flour beetle, Tenebrio,
exhibits optimal growth on diets containing 70%
carbohydrate. Tenebrio fails to develop however, if
the carbohydrate concentrations drop below 40%.
Carbohydrates are the major sources of metabolic
energy for plant-feeding insects. From the results
of this study, the concentration of carbohydrate in
the flours used in culturing T. castaneum ranged
from 57.34% in wheat flour to 62.41% in maize
making the flours suitable for the growth and
development of T. castaneum.
Maize, wheat and sorghum flours had a similar ash
content which was significantly lower in millet,
which might be responsible for the susceptibility
of millet flour to T. castaneum.
The sodium content in millet was low (0.37±0.01)
when compared to maize, millet and sorghum
flours. This might be due to variation in soil types
(Bulus, 2008). Millet flour was also high in iron. All
the flours used in this study had very low lead
content.
Ramputh et al. (2002) reported that significant
relationship between grain damage and soluble
phenolic content had a cause-and-effect
relationship. They also reported that phenolics are
well known to be directly involved in insect
resistance in many plants by antixenosis and
antibiosis. Adesuyi (1979) reported that factors
responsible for the resistance of stored products
to insects such as Tribolium spp. included presence
of toxic alkaloids or amino acids, insect feeding
deterrents, seed coat characteristics, digestive
enzyme inhibitors and kernel hardness.
Susceptibility of millet flour could be ascribed to
the low levels of anti-nutrients. Alkaloids,
flavonoids, saponins and tannins are known to
have antimicrobial activity as well as other
physiological activities. Many of the complexes
formed by phytate with metallic ions are relatively
insoluble; this accounts for a decrease in intestinal
absorption of minerals (Spivey Fox and Tao,
1989). Veillon (2011) identified 2-deoxy-D-
galactose, myo-inositol and phytate as potential
termiticides. These compounds showed promise
as potential control chemicals in the control of
subterranean termites, Coptotermes formosanus. The
negative correlation of oxalate (-0.18) and phytate
(-0.37) in millet compared with oxalate (0.75) and
saponin (0.37) in maize is probably responsible
for the significant reproductive success obtained
in millet flour. The phytate content in wheat flour
was highest in comparison to the other flours
tested. Therefore, it thus appears that phytate was
not a limiting factor in the growth and
development of T. castaneum.
The results obtained showed that millet flour was
the most susceptible to T. castaneum because it
recorded the highest number of larvae (138.25 ±
0.85), pupae (96.50 ± 0.41) and adults (103.50 ±
0.65) through the 56-day experimental period.
The highest number of larvae was also recorded
in millet flour in both the choice (65.00 ± 0.41)
and no-choice tests (171.75 ± 0.85).The larval
emergence of T. castaneum was observed on the
th
14 day for all four flours used in the experiment.
This agrees with Bulus (2008) that the emergence
of T. castaneum larva may take up to 8-12 days
depending on the environmental condition.
Pupae emerged on the four substrates under the
same environmental condition after 21 days of
infestation. This is in agreement with the report
of NRI (1996) that the pupal stage of T. castaneum
takes between 3-4 weeks on a suitable substrate.
Tribolium castaneum reared on the four cereal flours
completed their development in 35 days. This is in
agreement with the findings of Bulus (2008).
Insects show colour preference mostly to those
which resemble foliage, flower, or their hosts
(Reza and Parween, 2006). Lobdell et al. (2005)
observed that the egg parasitoid Trichogramma
ostriniae showed differential responses to egg
colour or the hosts as well as the background
colour in the Petri-dish arena while searching for
food. Generally, a wide range of insects exhibit
attraction towards yellow colour. The
Coccinellidae, Curculionidae and Scaraberidae
showed preference for yellow traps as observed
by Cross et al. (1976). The colour of the cereal
flours used in this study ranged from pink in
sorghum to white in maize; millet was grey in
colour while wheat flour was light-brown in
colour. Reza and Parween (2006) reported that
adult T. castaneum showed no preference for
coloured or white surfaces except for black. The
Kayode et al.: Influence of Four Cereal Flours on the Growth of Tribolium castaneum
514
results from the choice and no-choice test revealed
that T. castaneum had preference for millet flour
probably because of its grey colour. It is evident
from this study that other factors apart from the
antinutrient profile conferred resistance to maize
flour.
Millet flour was the most susceptible to Tribolium
infestation and was closely followed by wheat and
sorghum. The least susceptible was maize flour.
The presence of tannin and other anti-nutrients
inhibited the growth of the T. castaneum. This is
responsible for the reduced growth performance
of the beetle in sorghum and maize flours when
compared with wheat and millet flours.
Storage losses are becoming more serious as more
countries achieve self-sufficiency in cereal
production. Host plant resistance to storage
insects is a potential means of reducing post-
harvest losses of stored cereals and it is therefore
recommended. The importance of anti-nutrients
as a resistance factor for cereal flours needs to be
verified and possibly included as a breeding
objective.
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