IMPACT OF NEMATODE PEST MANAGEMENT STRATEGIES ON NEMATODE COMMUNITIES IN TOMATO PRODUCTION SYSTEMS IN ZIMBABWE By Cornel R. S. Massawe A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Crop Science Faculty of Agriculture University of Zimbabwe December 2010 ABSTRACT An analysis of soil nematode communities can be a useful tool for assessing the quality of soils and for the development of biological monitoring systems due to their intimate relationship of nematodes with their surrounding environment. In this study, soil sampling surveys were carried out in Chinamhora Communal Lands in Goromonzi District, the Botanic Gardens in Harare, and Henderson Research Station in Mazowe District at 0 – 15 and 15 – 30 cm depth to explore the effects of the land management systems and recommended tomato cropping sequences on the soil nematode communities. Glasshouse and field experiments, laid in randomized complete block design also were conducted in the 200/72008 and 2008/2009 seasons to examine the effects of chicken manure, Tagetes spp., nematicides and inorganic fertilizers on nematode communities in soils planted to tomato ( Solanum lycopersicum L.). Soil from the treatments were extracted using Baermann and wet-sieving techniques and nematodes from each sub-sample were identified into trophic groups i.e. bacterivores, fungivores, predators, plant-parasites and omnivores and then identified to genus and in the case of Meloidogyne spp. nematodes to species level. High abundance of nematode communities was recovered between 0 – 15 cm soil depth because it is the area of high biological activities. Soils at Henderson station had higher soil bulk density values that are not favourable for free-living nematodes. Predators and omnivores were more abundant in soils from the Botanic Gardens. Organic amendments were less consistent in the management of plant parasitic nematodes and they stimulated more populations of free living nematodes. Fenamiphos had long term negative effects on the abundances of fungivorous and omnivorous nematodes. Soybean cake showed higher reproduction factor for free-living nematodes and most plant parasitic nematodes reproduced more in the NPK fertilizer treatment. High structural SI and maturity MI index values were observed in less disturbed soils implying that the soils are fertile and well structured. Soil nematode communities responded to changes in agricultural management. This implies that nematodes and the indices derived from the analysis of their community structures have demonstrated that changes in soil management are either beneficial or deleterious to the soil ecology and are well suited to the role of bioindicators for soil health in agroecosystems. ii ACKNOWLEDGEMENTS Firstly, I am grateful for financial support from The Gatsby Charitable Foundation of the UK through the Nematology Initiative for Eastern and Southern Africa (NIESA) project, which enabled me to undertake this work. I would like to express my special gratitude to my mentors Drs. P. Jowah, Z. Sibanda and D. Hunt for their much needed advice and guidance throughout the whole period of this study. Although I cannot claim to have adequately dealt with many the excellent suggestions they made, I found their various suggestions most helpful in setting my own views. The head of Plant Protection Research Institute (PPRI), Harare is highly acknowledged for invaluable logistical assistance and granting me permission to use the laboratory facilities during the whole period of this study. In particular, I would like to mention Mr Akthar, S.S., Mr V.C. Mafirakurewa, Mr E. Mudira, N. Homela and the late Mrs M.N. Magunda both from the Nematology section at PPRI and Mrs I.G. Saunyama for assisting me in various ways. I owe thanks to Dr. Prof. H. Ferris and Dr K. Spence both in the Nematology Department at the University of California – Davis, in the USA for their interest, advice and relevant assistances on this study. Although it may be difficult to evaluate what one contributed in such professional interactions, I am certain I received much via added horizons of understanding. Colleagues and friends I worked together with at PPRI, Kutsaga Research Station, National Botanic Gardens, Henderson Research Station and farmers in Chinamhora Communal Lands in Goromonzi District in Mashonaland East Province deserve to be mentioned and thanked. I am indebted of thanks to the family of Eng. M. Sibanda of Mount Pleasant, Harare, who without their materials and moral support, my life in Zimbabwe would not have been the same. “Let them do good that they be rich in good works, ready to give, willing to share” (1 Timothy 6:18). Finally, any personal sacrifice that was required during the period of this study has certainly been negated by the benefits of gaining new insights into farming challenges and the fringe benefits such as gaining new friends, and experience of welcoming nature of Zimbabweans. iii DEDICATION To my family, for being a source of great encouragement, and To my late parents, baba Raphael and mama Anna who did not live to see the light of this day! iv ABBREVIATIONS g Gram s Second N Nitrogen P Phosphorus K Potassium Ca Calcium Mg Magnesium C:N Carbon-Nitrogen ratio G Granule 0C Degree Celsius WP Wettable Powder EC Emulsifiable Concentrate a.i. Active ingredient μm Micron metre ha Hectare km Kilometer cm 3 Cubic centimeter ppm Parts per millions rpm Revolution per minute H20 Water EDB Ethylene dibromide USDA United States Department of Agriculture ANOVA Analysis of Variance v CONTENTS ABSTRACT ............................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................... iii DEDICATION....................................................................................................... iv ABBREVIATIONS ................................................................................................ v TABLE OF CONTENTS .................................................................................... vi TABLES .................................................................................................................. x FIGURES ............................................................................................................. xii APPENDICES ..................................................................................................... xv CHAPTER ONE: GENERAL INTRODUCTION……………..…..………1 1.1 Agriculture in Zimbabwe ........................................................................... 1 1.2 Economic importance of tomato ................................................................ 2 1.3 Production and constraints ......................................................................... 3 1.4 Root-knot nematode (RKN) pests and their management ............................................................................................... 3 1.5 Impact of nematode management strategies on nematode communities ... 4 1.6 Justification ................................................................................................ 6 1.7 Objectives and Hypotheses ........................................................................ 7 1.7.1 Specific Objectives .................................................................................... 7 1.7.2 Hypotheses ................................................................................................. 8 CHAPTER TWO: LITERATURE REVIEW…………………….….………9 2.1 The Tomato - Origin, importance and production challenges……………………..………….…………………… ………...9 2.1.1 Origin and growth pattern of tomato plants ............................................... 9 2.1.2 Importance of tomato .............................................................................. 10 2.1.3 Production challenges with particular reference to Root-knot nematodes ............................................................................... 10 2.2 Behaviour of and control of Root-knot nematodes (RKNs) .................... 10 2.2.1 Life cycle and behaviour of RKNs (Meloidogyne spp.)……….………..11 2.2.2 Effect of nematodes on plant growth and yield ....................................... 12 2.2.3 Management strategies to control RKN .................................................. 13 2.2.3.1 Host Plant Resistance .......................................................................... 13 2.2.3.2 Cultural control ................................................................................... 14 Crop rotation ............................................................................................ 14 Organic amendments ............................................................................... 15 2.2.3.3 Biological control ................................................................................ 16 2.2.3.4 Chemical control ................................................................................. 18 2.3 Impact of nematode management strategies on nematode communities ... 20 2.4 Spatial distribution of nematode communities ............................................ 21 vi 2.4.1 Vertical distribution of nematodes........................................................... 21 2.4.2 Horizontal distribution of nematodes ...................................................... 22 2.5 Influence of abiotic and biotic factors on nematode communities ...........................................................................................