Abstract:
Sitophilus zeamais Motsch. (maize weevil) and Callosobruchus maculatus F. (cowpea
weevil) pose formidable challenges to agricultural productivity and food security,
causing substantial post-harvest losses in grains and legumes. This study investigates
the potential effects of ethanol and aqueous leaf extract of soursop (Annona muricata)
on these two economically significant pest species. The study employed a
comprehensive biochemical laboratory analysis, and evaluated the impact of four (4)
varying concentrations of ethanolic and water extract of soursop leaf on the mortality,
and reproductive ability of the two insect species. It further assesses the potential
effect of the two soursop extracts on the quality of stored maize and cowpea. The
study findings showed that ethanol was able to extract phytochemicals such as
alkaloids, tannis, and triterpenoids which were absent in the water extract. The results
of the study further revealed that both ethanol and water extract exhibited significant
difference in insecticidal properties against cowpea weevils with varying degree of
efficacy (p-value<0.05). Higher mortality in the insects was recorded in the treatment
with water extract. On the contrary, there was no statistical difference (p-value>0.05)
in various concentrations of the two soursop extract on the mortality of S. zeamais and
C. maculatus. Moreover, comparatively to the control, there was less reduction in
weight and the overall quality of the cowpea and maize grains with treatment
application. Lastly, there was less increase in the progeny of S. zeamias and C.
maculatus in the treatment as compared to the untreated. It is therefore imperative to
conduct field trials in actual grain and legume storage facilities to validate the efficacy
of soursop extract under real world conditions.
Description:
A thesis submitted to the Department of Biology Education,
Faculty of Science Education, School of Graduate Studies,
in partial fulfillment of the requirements for the award of
Master of Philosophy
(Biology Education)
in the University of Education, Winneba
