ABSTRACT

Rice is an economically important crop and the most important staple food for the world's population. The rice plant is vulnerable to various kinds of pests, from the field to the stored grains. The aim of the study is to evaluate three plant leaf powders, scent leaf (Ocimum gratissimum), neem (Azadirachta indica) and paw-paw (Carica papaya) in the control of rice weevils Sitophilus oryzae on stored rice grain. Then 2g of the plant leaf powders were admix with the rice grain at the quantities of 3 g, 6g, 9g and 12g per 20g of rice. In the control, no treatment was used. The plant leaves were dried under room temperature and ground into fine powders. The powders were put into separate air tight containers to ensure active ingredients were not lost before use. The experimental design adopted for the experiment was Complete Randomized Design (CRD) and each treatment was replicated four times for each experiment. Ten (10) adult S. oryzae unsexed (taken from stock culture kept in the laboratory) were introduced into each vial including the control and were subsequently covered with muslin cloth held tightly in place by a rubber band to avoid their escaping. The experiments were monitored for 96 hours. The results showed that all the plant leaf powders were good grain protectants. O. gratissimum recorded its highest mortality of 40 in 6g, 9g, and 12g at 48 hours, A. indica had its highest mortality of 40 in 6g and 12g at 48 hours while C. papaya recorded its highest mortality of 40 in 9g and 12g at 48 hours. The highest total insect mortality recorded throughout the experiment was in O. gratissimum 159(99.36%) followed by A. indica 154(96.25%) and C. papaya 148(92.50%). No mortality was recorded in the control experiment. These plant leaves powders especially O. gratissimum should be incorporated into grain protection practice of resource poor farmers and small scale rice dealers.

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgements iv

Table of contents v

List oftables vi

List offigure vii

Abstract viii

Chapter One:Introduction and literature review 

1.1.1 Aims and obj ectives ofthe study

1.1.2 Justification

1.2 Literature Review

1.3.1 Insect pests ofstored grains

1.3.2 Rice weevils {Sitophilus oryzae)

1.3.2.1 Distribution and habitat ofSitophilus oryzae 4

1.3.2.2 Life cycle ofSitophilus oryzae 5

1.3.2.3 Damaging rice grains 6

1.3.3 Control ofrice weevil 7

1.3.3.1 Traditional control 7

1.3.3.2 Chemical control 8

1.3.3.3 Alternative strategies for stored products pest management 9

1-3.3.3.1 The use ofplant-based protectants for the control ofpost-harvest insect pests 10

1.3.3.3.2 Classification ofbio-potential plant products 11

1.3.3.4 Plants ofinterests

Chapter Two: Materials and Methods

Study Area

Insect culture

Rice used for the experiment.

Collection and preparation ofplant materials

Methodology

Statistical analysis

Chapter Three: Results

Results

3.1.1: Mortality rate ofS. oryzae in Ocimum gratissimum

3.1.2: Mortality rate ofS. oryzae in Azadirachta indica

3.1.3: Mortality rate ofS. oryzae in Caricapapaya

3.1.4 Mortality rate ofS.oryzae in all the botanical powders.

Chapter four: Discussion and conclusion

Discussion 27

4.2 Conclusion 28

4.3 Recommendations 29

References 

List of tables

Table 3.1 Mortality rate ofS. oryzae treated with Ocimum gratissimum in stored rice 20

Table 3.2 Mortality rate ofS. oryzae treated with Azadirachta indica in stored rice 22

Table 3.3 Mortality rate ofS. oryzae treated with Carica papaya in stored rice 24

List of figure

Figure 1.1 Life cycle ofrice weevils, Sitophilus oryzae. 6

Figure 3.1: Comparing the mortality rates ofS. oryzae in all the treatments. 26