International Journal of Horticulture, 2017, Vol.7, No. 9, 64-75
73
5 Materials and Methods
5.1 Insect culture
The initial culture of the insect used was gotten from an existing culture in the food storage research laboratory of
the Department of Biology, Federal University of Technology, Akure. The insect was reared on an uninfested
cowpea collected from National seed research institute, Ibadan, Nigeria. The insects were cultured at temperature
of 28±2ºC and relative humidity of 75±5% inside plastic container covered with muslin cloth to disallow the
escape of the insect and as well disallow the entry of other insects that may be a parasitoid of
C. maculatus
. The
culture was maintained by replacing the devoured seeds with new uninfested seeds.
5.2 Collection of plant materials
The culture nuts used were collected from an open field from a mature cashew tree in Ado-Ekiti, Ekiti State,
Nigeria. The nuts were sun dried between 8.00 am to 12.00 pm, in order to ensure their phytochemicals are not
denatured by extreme temperature. The leaves, stem bark and the root bark were collected from an open field
inside Ekiti State University, Ado-Ekiti, Nigeria. These parts were air dried in the laboratory of Department of
Plant Science of the University. After drying, the samples were separately pulverized into fine powder and were
kept inside separate airtight plastic
containers.
5.3 Extraction of the plant extracts
The ethanolic extracts of the plant powders were made by separately soaking 50 g of each of the plant powders in
100 ml of ethanol for 3 days. The hot water extracts of each of the plant parts were made by separately soaking
50g of the powders in hot water of 60
o
C temperature for 30 minutes in a heating mantle. Then the extracts were
removed from the heating mantle. Cold water extracts of the plant parts were made by separately soaking the
powders of the plant parts inside water of 3
o
C temperature stored for 3 days inside refrigerator to maintain the
temperature. The extracts were stirred early in the morning for the period of extraction in order to ensure uniform
extraction of the extracts. Irrespective of the extraction method used, the extracts were separated from the solvents
used by sieving using muslin cloth. The following extracts were made:
Nut cold extract (NC), stem cold extract (SC), root cold extract (RC), leaf cold extract (LC), nut hot extract (NH),
stem hot extract (SH), root hot extract (RH), leaf hot extract (LH), nut ethanolic extract (NE), stem ethanolic
extract (SE), root ethanolic extract (RE) and leaf ethanolic extract (LE).
5.4 Effect of cashew plant parts extracts on mortality of
Callosobruchus maculatus
Aliquot of 0.2, 0.4, 0.6 and 0.8 ml which corresponds to 1.0 %, 2.0 %, 3.0 % and 4.0 % v/w plant extracts were
separately pipetted into Petri dishes (9 cm diameter) containing 20 g of disinfested cowpea seeds. Three replicates
per treatment were prepared. Untreated cowpea seeds were set as control in triplicate. The cowpea seeds and the
extracts were thoroughly mixed with the aid of a glass rod to ensure uniform coating of the extracts on the seeds.
The seeds were then air-dried for 4 hours before introducing the insect
.
20 adult
C. maculatus
were introduced
into each petri-dish and they were observed daily for 4 days for mortality. After every 24 hours, the numbers of
dead beetles were counted. The percentage adult mortality was calculated using the formula below
:
All the insects (both dead and live) were removed on the fifth day of observation and oviposition was recorded.
The treatments were left for 20 days and adult emergence was counted till no emergence was observed for five
days. The percentage adult emergence was calculated with the formula below:
