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Molecular Entomology
12
control and T
n
is the number of emerged insects in the
treated container.
Percentage weight loss of the cowpea seeds was
determined by re-weighing after 35 days and the %
loss in weight was determined as follows:
Difference in weight 100
% weight loss=
—————————×——
Initial weight 1
After re-weighing, the numbers of damaged cowpea
seeds were evaluated by counting wholesome seeds
and seeds with bruchid emergent holes. Percentage
seed damaged was calculated as follows:
No. of seeds damaged with emergent hole 100
% seed damaged=
————————————×——
Total number of seeds 1
Beetle Perforation Index (BPI) used by Fatope et al.
(1995) was adopted for the analysis of damage. Beetle
perforation index (BPI) was defined as follows:
% treated cowpea seeds perforated 100
BPI=
——————————————×
——
% control cowpea seeds perforated 1
BPI value exceeding 50 was regarded as enhancement
of infestation by the weevil or negative protectability
of the extract tested.
Cowpea seeds weighing 20g each that have been
previously treated with
A. boonei
extracts for 30, 60
and 90 at rate 0.3ml was used for this experiment.
Similar parameters described were assessed for the
persistent toxicity
A. boonei
extracts of to cowpea
bruchid.
Data were subjected to analysis of variance (ANOVA)
and treatment means were separated using the New
Duncan’s Multiple Range Test. The ANOVA was
performed with SPSS 16.0 software (SPSS, Inc. 2007).
2 Results
Table 1 shows and the effects of contact toxicity of
A.
boonei
leaf, stembark and root extracts obtained by
kneading method on adult mortality of
C. maculatus
after 1, 2, 3 and 4 days of infestation and 30, 60 and
90 days of post treatment. The stem bark extract
completely evoked 100% mortality of adult
C.
maculatus
at concentration tested after 3 days of
application. This is followed by leaf extract causing
100% mortality of adult cowpea bruchid while the
least toxic was root extract evoking 87.50% adult
C.
maculatus
after 4 days of application (Table 1).
Stem bark extract caused 70% adult mortality of
C.
maculatus
at rate 0.3 ml/ 20g of cowpea seeds after 30
days of post treatment. This is followed by leaf extract
causing 57% mortality of cowpea bruchid at rate
0.3ml per 20g of cowpea seeds after 30 days of post
treatment. The least toxic extract was root evoking
37.5% adult
C. maculatus
at rate 0.3ml per 20g of
cowpea seeds after 30 days of post treatment (Table 2).
At 60 days of post treatment, 60% adult mortality of
cowpea bruchid was recorded on cowpea seeds treated
with stem bark extract. At 90 days of post treatment,
42% adult mortality of cowpea bruchid was recorded
on cowpea seeds treated with stem bark extract at rate
0.3 ml. Generally, percentage adult mortality of
C.
maculatus
decreases with length of storage period
(Table 2). This shows that
A. boonei
stem bark had the
greatest insecticidal potential, while A. boonei the
least effective was
A. boonei
root.
Tables 3 and 4 shows the effects of
A. boonei
leaf,
stem bark and root extracts obtained by kneading
method on oviposition, adult emergence and reduction
in progeny development of adult
C. maculatus
after 4
days of infestation, 30, 60 and 90 days of post
treatment. Stem bark extract completely protected
cowpea seeds from being damaged and 100%
reduction in progeny development after 4 days of
application (Table 3). Leaf extract of
A. boonei
completely protected cowpea seeds and 100%
reduction in progeny development at rate 0.4ml after 4
days of application. The results obtained on cowpea
seeds treated with root extract were significantly
different from untreated cowpea seeds (Table 3).
At 30 days of post treatment,
A. boonei
stem bark
extract reduced the number of eggs laid by cowpea