Post-harvest loss due to pests in dried cassava chips and comparative methods for its assessment. - A case study on small-scale farm households in Ghana.

Table of Contents

Dissertation

zur Erlangung des akademischen Grades
doctor rerum agriculturarum
(Dr. rer. agr.)

eingereicht an der Landwirtschaftlich-Gärtnerischen Fakultät
der Humboldt-Universität zu Berlin
von Dipl. Agrar. Ing., M.Sc., Elke Stumpf
aus Bietigheim-Bissingen
Präsident der Humboldt-Universität zu Berlin
Prof. Dr. Dr. h.c. H. Meyer
Dekan der Landwirtschaftlich-Gärtnerischen Fakultät
Prof. Dr. Dr. h.c. E. Lindemann

Gutachter:
Prof. Dr. Dr. h.c. Helmut Bochow · Prof. Dir. Dr. Christoph Reichmuth
Tag der mündlichen Prüfung:
29.1.1998

Copyright: GTZ and Dr. Elke Stumpf
The copyright of this publication is vested in the "Deutsche Gesellschaft fuer Technische Zusammenarbeit (GTZ) GmbH" and Dr. Elke Stumpf. Applications for permissions to reproduce this publication, in whole or in part, by any method or process, should be addressed, with a statement of purpose and extend of the reproduction desired, to GTZ - Stabsstelle 01, Postfach 5180, D-65726 Eschborn, Germany.

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Table of Contents

Acknowledgements

1. Introduction

1.1 Importance of cassava
1.2 Problem analysis
1.3 Objectives

2. Background information on Ghana

2.1 Description of the study area in the Northern Region
2.2 The cassava plant
2.3 Traditional drying and storage structures of dried cassava chips

3 Investigations under controlled conditions

3.1 Materials and methods

3.1.1 Existing loss-assessment methods

3.1.1.1 Gravimetric Method [GM]
3.1.1.2 Volumetric/Gravimetric Method [VGM]
3.1.1.3 Visual Damage Scale Method [VDSM]

3.1.2 Development of a new loss-assessment method [MM]
3.1.3 Experimental design

3.1.3.1 Test insects

3.1.4 Qualitative analysis
3.1.5 Statistical analysis

3.2 Results

3.2.1 Pre-testing of the newly developed MM
3.2.2 Experiments with loss assessment methods
3.2.3 Comparison of four different loss-assessment methods
3.2.4 Investigations of insect pest population dynamics
3.2.5 Investigations into qualitative losses of cassava chips

4 Investigations under field conditions

4.1 Materials and methods

4.1.1 Farm survey
4.1.2 Station study
4.1.3 Survey preparations
4.1.4 Local cassava varieties
4.1.5 Qualitative analysis of dried cassava chips
4.1.6 Socio-economic study on cassava chip storage
4.1.7 Statistics

4.2 Results

4.2.1 Farm and station study
4.2.2 Relationship of different methods to boreholes
4.2.3 Comparison of four different loss-assessment methods
4.2.4 Causes of losses

4.2.4.1 Classification of insects and development rates

4.2.5 Cumulative weight loss
4.2.6 Qualitative analysis of cassava chips
4.2.7 Economic study of cassava chip storage

4.2.7.1 Economic evaluation of cassava chip storage

5 Discussion

5.1 Loss-assessment methods
5.2 Causes of losses
5.3 Other losses within the post-harvest system
5.4 Economic environment of the farm- household
5.5 Conclusions
5.6. Recommendations

6 Summary

7 Bibliography

8 Appendix