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International Journal of Horticulture 2014, Vol.4, No.17, 1
-
6
http://ijh.biopublisher.ca
4
Discussion
Resultant negative effects of synthetic chemicals used
in the protection of crops and crop products have been
noted by scientists and have directed research toward
identifying effective, environment friendly and
biodegradable pesticides (Talukder and Howe, 2000;
Elhag, 2000; Ofuya, 2003). Products such as ashes,
sand and powder from leaves of some plants have
been investigated for effective management of stored
crop insect pests (Lajide et al., 1998; Adebayo and
Ibikunle, 2014). Oil and powder obtained from several
plants have been reported to provide sustained
protection for the stored grains (Lale and Ajayi, 1996;
Ogunwolu and Odunlami, 1996; Oni, 2014).
The powder of hyptis effected insecticidal properties
by killing adult
C. maculatus
over the period of
exposure thus seems to possess protectant ability. The
ability of the plant powder to cause mortality of adult
beetle on grains can be attributed to contact toxicity of
the powder on the beetle. The effectiveness of some
plant powders in controlling beetles
by causing adult
mortality of the insects had been reported by Lajide
et al. (1998). The result of this study was in
agreement with the work of Lajide et al
.
(1998).
Similarly effects of plant materials as crop seeds
protectants have also been observed in the treatment
of cowpea and maize weevils where adult insects
were killed through contact toxicity (Ofuya and
Dawodu, 2002; Asawalam et al.,
2007).
Lale and Abudulrahman (1999) reported that the
powders of some plants are effective in reducing
egg-laying and adult emergence of the bruchid. In this
study powder of
Hyptis suaveolens
showed to be
potent or effective at reducing oviposition and adult
emergence of
C. maculatus
especially when treated
with higher dose of the powder. Eggs were laid on
cowpea seeds but their hatchability was reduced as
earlier reported by Lale and Mustapha (2000).
Previous work on components of some bioactive plant
species showed that they caused mortality, oviposition
deterrence and or ovicidal action resulting in reduced
progeny production of stored product insects
(Aswalam, 2007; Oni, 2014). However the powder in
this present study might have invoked ovicidal action
rather than oviposition deterrence. As result of
reduced oviposition and consequent few adults
emergence loss in weight due to adult activity was
least in the treated seeds (Idoko and Adebayo, 2011).
In this study germinability of seeds of Ifebrown was
negatively affected and was contrary to the previous
works of (Murdock and Shade, 1991; More et al.,
1996) who reported that germination of cowpea
seeds was not adversely affected. The result of
germination test recorded for oloyin and ifebrown
cowpea does not warrant rejection of the positive
findings from this study.
Conclusion and recommendation
Results from this study have proved that tested rates
of hyptis leaf powder were potent against bruchid
beetles. Its protectant properties were observed from
the mortality caused and reduction in oviposition,
adult emergence and weight loss occasioned by the
beetle’s infestation.
Although, results from the study did show insecticidal
activities of
Hyptis suaveolens
powder, it is
recommended that higher rates and other components
of the plant should be further investigated for effective
management of
Callosobruchus maculatus
(F.).
Materials and Methods
Study sites
The experiment was carried out at the entomology
laboratory of the Department of Crop, Soil and Pest
Management, Federal University of Technology Akure
(FUTA), Ondo State, Nigeria. All studies were
conducted under the laboratory conditions at 25-28
o
C
and 65-75% R.H.
Collection of materials
Fresh unifested Oloyin beans were obtained from
Oja-Oba and Ife-brown was obtained from Ondo State
ADP. The leaves of
H. suaveolens
were collected from
a nearby field at the Teaching and Research Farm,
FUTA by Mr. G. F. Hassan, a technologist in the
pathology laboratory of the department.
Preparation of plant materials
The plant materials were air dried for two weeks in a
well-ventilated place. The powder was obtained by
blending the dried leaves using a warring blender at
the laboratory of the department of Crop, Soil and
Pest Management. The blended material was sieved
with 200mm aperture metal sieve to obtain a fine
powder which was kept in an air-tight container and
stored until it was used (Egwuyenga,1997).
Insect culture
Cowpea seeds infested by
C. maculatus
were collected
from Oja-Oba, Akure and brought to the laboratory.