Repellent Effect and Qualitative Phytochemical Analysis of Lemongrass (Cymbopogon citratus) and Waterhyacinth (Eichhornia crassipes) against Cowpea Beetle (Callosobruchus maculatus)
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Date
2021
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
Cowpea (Vigna unguiculata) is the most economically important leguminous crop in the worldwide,
it is vulnerable to the infection of seed by cowpea beetle (Callosobruchus maculatus) in storage. The
application of synthetic insecticide for the control of such insect pest leads to numerous hazardous
effect of environment and human. Thus aim to identify the botanical products to control the
C.maculatus. Lemongrass widely used as a medicinal herb in Sri Lanka. It has a subtle citrus flavor
and can be dried and powdered or used fresh. In Sri Lanka water hyacinth (Eichhornia crassipes) is
most problematic invasive aquatic weed. Therefore the study has been conducted to confirm the
presence of insecticidal properties in this weed in order to use the weed in a beneficial manner rather
destructing without any benefits. The purpose of this research is to do the phytochemical analysis and
compare the secondary metabolites present in both plants and the repellency ability of powder and
methanol extract of both plants. Selected plants were sun dried and pulverized into fine powder.
Powders were dissolved in methanol to produce the extract. The powder and methanol extract were
used for the bioassay. All the experiments were done at the laboratory condition at 28-30°C
temperature and 74-80%RH. Repellency was evaluated by observing the behavior of beetles exposed
to treated and untreated seeds in choice chamber and using petridish mehod. All this extracts and
powders showed varying degree of repellent activity against cowpea beetle. However lemongrass
methanol extract showed significantly higher repellent activity against beetles in choice chamber
method (1.66) and petridish method (0.00), during storage time. The phytochemical analysis stated
that the methanol extract of lemongrass had more phytochemicals, namely phenols, tannin,
terpinoids, quinones, steroids, glycosids, reducing sugar, and flavanoids than the water hyacinth
methanol extract.
Keywords: Cowpea beetle; Lemongrass; Water hyacinth; Methanol form; Powder form
Description
Keywords
Agriculture, Crop Production Technology, Crop Production, Pest Control