Classification of oilseed rape visiting insects in relation to the sulphur supply Von der Fakultät für Lebenswissenschaften der Technischen Universität Carolo-Wilhelmina zu Braunschweig zur Erlangung des Grades einer Doktorin der Naturwissenschaften (Dr. rer. nat.) genehmigte D i s s e r t a t i o n von Fahmia Aljmli aus Homs, Syria 1. Referent: apl. Professor Dr. Ewald Schnug 2. Referent: apl. Professor Dr. Dirk Selmar eingereicht am: 25.06.2007 mündliche Prüfung (Disputation) am: 30.08.2007 Druckjahr 2007 Acknowledgements I take this opportunity with much pleasure to thank all the people who have helped me through the course of my journey towards producing this thesis. First, I would like to express my deepest thanks to my supervisors: Prof. Dr. Dr. Ewald Schnug for his wise advices and all aspects of this project. I would like to thanks my committee members Prof. Dr. Dirk Selmar, Prof. Dr. Wolfgang Büchs and Prof. Dr. Robert Kreuzig for reviewing my thesis and taking time out to attend my oral defense. I would like to thank all members and colleagues of the institute of plant nutrition and soil science (FAL). Especial thanks go to Dr. Elke Bloem for their guidance, suggestions, discussions and the interpretations of the data during my study, which were always fruitful. I would like to thank her for everything that I learnt from her. Without her, this thesis would not have been possible. I would like to express my gratitude to all members in the institute of plant protection in field crops and grassland at BBA (in Braunschweig), especially to Prof. Dr. Büchs, I learnt a lot from him, which I am sure will be useful in different stages of my life. Special thanks also go to Dr. Prescher and Dr. Schlein, who always were available when I needed their advises. I am thankful to Ruth Polok and Fabian Zelmanski for their helps during my labor works. No words, perhaps can express acknowledgement and gratitude to parents, brothers and sisters. I would like to give my special thanks to my husband Mamdoh and my daughter Nour whose patient love enabled me to complete this work. Table of contents i TABLE OF CONTENT Table of content.……………………………….……………………………………..…….i List of figures.......................................................................................................................iii List of tables.........................................................................................................................ix List of tables and figures in the appendix.........................................................................xi 1 Introduction...................................................................................................................... 1 1.1 Biology and damage of important pests in European oilseed rape cropping............... 4 1.2 Influence of fertilisation on the infestation of crops by insects................................. 10 1.3 Importance of secondary plant metabolites of Brassica napus in host-plant selection .................................................................................................................................... 13 1.4 Management strategies to reduce the infestation of oilseed rape by insect pests ...... 16 1.5 Response of generalist and specialist insects to defence compounds........................ 17 1.6 Objectives of this study.............................................................................................. 18 2 Material and Methods ................................................................................................... 19 2.1 Description of study sites........................................................................................... 19 2.2 Experimental design...................................................................................................21 2.3 Sampling procedures of oilseed rape visiting insects ................................................ 22 2.3.1 Sampling of adult insects................................................................................... 24 2.3.2 Sampling of eggs and larvae.............................................................................. 30 2.4 Analysis of plant material and larvae......................................................................... 35 2.4.1 Analysis of plant samples .................................................................................. 35 2.4.2 Analysis of larvae .............................................................................................. 38 2.5 Classification of insects ............................................................................................. 39 2.6 Statistical analysis...................................................................................................... 40 3 Results ............................................................................................................................. 41 3.1 Influence of S-fertilisation on the S-status of oilseed rape and S-containing secondary metabolites................................................................................................ 41 3.2 Influence of S-fertilisation on the mineral composition of larvae collected from oilseed rape ................................................................................................................ 43 ii Table of contents 3.3 Influence of S-fertilisation on the number of pollen beetle (Meligethes spp.) .......... 49 3.4 Influence of S-fertilisation on the number of stem-mining weevils, the rape stem weevil (Ceutorhynchus napi) and the cabbage stem weevil (Ceutorhynchus pallidactylus).............................................................................................................. 54 3.5 Influence of S-fertilisation on the number of the cabbage seed weevil (Ceutorhynchus obstrictus)........................................................................................ 61 3.6 Influence of S-fertilisation on the number of Brassica pod midge (Dasineura brassicae)................................................................................................................... 67 3.7 Influence of S-fertilisation on the number of root flies (Delia radicum, Delia platura and Delia florilega).................................................................................................... 73 3.8 Influence of S- and N-fertilisation on the number of cabbage aphid (Brevicoryne brassicae)................................................................................................................... 80 3.9 Influence of S- and N-fertilisation on the occurrence of Staphylinidae and Tachyporus (adults and larvae).................................................................................. 82 3.10 Influence of S-fertilisation of oilseed rape on the number of miscellaneous insects 90 4 Discussion........................................................................................................................ 93 4.1 Significance of experimental conditions on infestation of oilseed rape with insects.. .................................................................................................................................... 93 4.2 Relationship between the S-nutritional status of oilseed rape and oilseed rape visiting insects......................................................................................................................... 96 4.3 Relationship between S-fertilisation and beneficial insects of oilseed rape............ 110 4.4 Relationship between N-fertilisation and infestation of oilseed rape with different pests and beneficial insects ...................................................................................... 113 5 Summary....................................................................................................................... 117 6 References..................................................................................................................... 123 7 Glossary ........................................................................................................................ 142 8 Appendix....................................................................................................................... 143 List of figures iii LIST OF FIGURES Fig. 1.1: Important pest species which attack different plant parts of oilseed rape. ........ 2 Fig. 1.2: The life cycle of Meligethes spp. on oilseed rape.............................................. 5 Fig. 1.3: Life cycle of Dasineura brassicae..................................................................... 8 Fig. 2.1: Precipitation and temperature during the growing season 2004...................... 20 Fig. 2.2: Precipitation and temperature during the growing season 2005...................... 20 Fig. 2.3: Distribution of traps for the monitoring of oilseed rape visiting insects during different plant growth stages in the field trials. ............................................... 23 Fig. 2.4: The sampling of oilseed rape visiting insects using an emergence traps......... 25 Fig. 2.5: Different parts of the emergence traps............................................................. 26 Fig. 2.6: The collection of oilseed rape visiting insects by using a beating tray............ 28 Fig. 2.7: The sampling of oilseed rape visiting insects by using the Vortis’ suction sampler............................................................................................................. 29 Fig. 2.9: Meridian splitting in a main stem caused by larvae