| dc.description.abstract | The study was an experiment carried out at the Nutrition and Bio-analytical laboratory at
NaCRRI, Uganda from November 2016 to October 2017. The aim of the study was to investigate
the efficacy of pawpaw leaf powder and liquid extracts in seed protection against bean weevils in
storage over a time period. The specific objectives were; to determine the concentration of the
secondary metabolites in pawpaw liquid extracts and pawpaw leaf powder; determine the
effectiveness of pawpaw leaf powder, water and ethanol extracts in the control of bean weevils
and to establish the effect of pawpaw leaf powder on seed germinability. Methods used in the
study were; phyto-chemical screening of the secondary metabolites such as total tannins, total
phenolics, total flavonoids, total alkaloids and total anti-oxidant activity. Pawpaw leaf extracts
were prepared in water and ethanol at concentrations of 5%, 10%, 15% and 0% (control) where
no treatment was applied. Pawpaw leaf powder was also applied at varying rates of 5%, 10%
and 15% (w/w of sample) to bean seeds of NABE 6 cultivar. Pyto-chemical screening results
revealed that the highest concentration of secondary metabolites in extracts was for total anti oxidants at 5.5% in the pawpaw leaf accession M-5 which was significantly higher (P<0.05) than
in other accessions. Powder treatment had the highest concentration of total anti-oxidants at
11.6% in M-2 followed by total tannins at 5.2%. Generally, pawpaw leaf powder had a higher
concentration of secondary metabolites in the different pawpaw leaf accessions as compared to
the liquid extracts. Pawpaw leaf powder provided the most effective control measure of bean
weevils in bean storage. Pawpaw leaf powder significantly (P<0.05) reduced on the number of
damaged seeds, the percentage weight loss of bean seeds, insect mortality, F1 progeny
emergence. The same trends were observed from week one up to week 12 of the experimental set
up. Pawpaw water extracts had the least effect in the control of weevils. Pawpaw leaf ethanol
extract also had a significantly higher (P<0.05) mortality rate at 15% concentration as compared
to other treatment levels. Pawpaw leaf powder did not significantly reduce on the germination
percentage of the different bean varieties (P<0.05). It was discovered that the effect of pawpaw
leaf powder water and ethanol extract in the control of bean weevil were doze dependent with
10% being the most ideal for powder extracts. The effectiveness of pawpaw leaf extracts in the
control of bean weevils is attributed to the higher concentration of the different secondary
metabolites in the leaves. The study demonstrated that pawpaw leaves could act as cost effective
bio pesticides with potential to substitute synthetic insecticides for the control of bean weevils in
stored beans | en_US |
