EESTI MAAÜLIKOOL ESTONIAN UNIVERSITY OF LIFE SCIENCES OILSEED RAPE PESTS AND THEIR PARASITOIDS IN ESTONIA RAPSI KAHJURID JA NENDE PARASITOIDID EESTIS EVE VEROMANN A Thesis for applying for the degree of Doctor of Philosophy in Entomology Väitekiri Filosoofiadoktori kraadi taotlemiseks entomoloogia erialal Tartu 2007 Institute of Agricultural and Environmental Sciences Estonian University of Life Sciences According to verdict No 18 of April 23, 2007 the Doctoral Committee for Agricultural and Environmental Sciences of Estonian University of Life Sciences has accepted the thesis for the defence of degree of Doctor of Philosophy in Entomology. Opponent: Dr. Samantha M. Cook Plant & Invertebrate Ecology Division Rothamsted Research Harpenden, UK Supervisors: Prof. Anne Luik Institute of Agricultural and Environmental Sciences Estonian University of Life Sciences Dr. Luule Metspalu Institute of Agricultural and Environmental Sciences Estonian University of Life Sciences Defence of the thesis: Estonian University of Life Sciences, room 1A5, Kreutzwaldi 5, Tartu on June 15, 2007, at 10.00 The publication of this thesis was funded by the Estonian University of Life Sciences © Eve Veromann, 2007 ISBN 978-9985-830-73-4 CONTENTS LIST OF ORIGINAL PUBLICATIONS ................................... 6 INTRODUCTION ................................................................... 7 1. REVIEW OF THE LITERATURE ............................................ 8 1.1. Oilseed rape pests ............................................................... 8 1.2. Parasitoids of oilseed rape pests ........................................... 9 2. AIMS OF THE STUDY ............................................................. 12 3. MATERIAL AND METHODS ................................................. 13 3.1. Study area .......................................................................... 13 3.2. Insect sampling .................................................................. 13 3.3. Statistical analysis ............................................................... 14 4. RESULTS ................................................................................... 15 4.1. Species composition and phenology of oilseed rape pests ........................................................................... 15 4.2. Species composition and phenology of parasitoids of oilseed rape pests ............................................................ 16 4.3. Impact of cropping system and insecticide use on the abundance of oilseed rape pests and their parasitoids .......................................................................... 18 5. DISCUSSION ........................................................................... 20 5.1. Comparison of pest species in winter and spring oilseed rape ........................................................................ 20 5.2. Comparison of parasitoids of oilseed rape pests in winter and spring oilseed rape ........................................ 21 5.3. Comparison of impact of cropping systems and insecticide use on the abundance of oilseed rape pests and their parasitoids ................................................... 23 6. CONCLUSIONS ...................................................................... 25 REFERENCES ........................................................................... 27 SUMMARY IN ESTONIAN ..................................................... 32 ACKNOWLEDGEMENTS ....................................................... 35 ORIGINAL PUBLICATIONS .................................................. 37 CURRICULUM VITAE ............................................................ 78 LIST OF PUBLICATIONS ....................................................... 82 LIST OF ORIGINAL PUBLICATIONS This thesis is a summary of the following papers, which are referred to by Roman numerals in the text. The papers are reproduced by kind per- mission of the publishers of the following journals: Entomologica Fen- nica (I), Agricultural and Food Science (II), International Journal of Pest Management (IV) I Veromann, E., Luik, E., Metspalu, L. & Williams, I. 2006. Key pests and their parasitoids on spring and winter oilseed rape in Es- tonia. Entomologica Fennica 17, 400–404. II Veromann, E., Tarang, T., Kevväi, R., Luik, A. & Williams, I.H. 2006. Insect pest and their natural enemies on spring oilseed rape in Estonia: impact of cropping systems. Agricultural and Food Sci- ence, 15, 61–72. III Veromann, E., Luik, A. & Kevväi, R. 2006. Oilseed rape pests and their parasitoids in Estonia. Bulletin IOBC/wprs, Integrated Con- trol in Oilseed Crops, 29 (7), 165–172. IV Veromann, E., Kevväi, R., Luik, A. & Williams, I.H. 2007. Do cropping system and insecticide use in spring oilseed rape affect the abundance of pollen beetles (Meligethes aeneus Fab.) on the crop? – International Journal of Pest Management, in press. 6 INTRODUCTION Oilseed rape (Brassica napus L.) is one of the most important oilseed plants cultivated in temperate regions. The expansion of the growing area of rape in Europe has resulted in an increase in the number of pests (Büchi, 1996; Cook et al., 1999; Hokkanen, 2000). In Estonia, the area sown to the crop has increased greatly during the last fifteen years, with 50,400 hectares grown in 2004 (Statistics Estonia, 2006). The manage- ment of pests on the European oilseed rape crop still relies heavily on chemical pesticides, most often applied routinely and prophylactically, without regard to pest incidence, at best according to threshold values of the pest population (Williams, 2004). This leads to the over-use of chemical pesticides, which reduces the economic competitiveness of the crop, brings on the development of resistance to pesticides and also threatens biological diversity. Pesticides also kill natural agents of bio- logical control that represent a resource with a great potential benefit to farmers and consumers (Alford et al., 1995; Williams & Murchie, 1995; Walters et al., 2003). By killing the natural enemies of pests, pesticide use has to be increased further to achieve pest control (Pickett et al., 1995; Murchie et al., 1997). Recent advances in insect management of the pests of oilseed rape have emphasised the important role of natural enemies within integrated pest management systems for the crop (Williams, 2004). To develop eco- nomically-viable and environmentally-acceptable crop management strategies for oilseed rape to maximise the biocontrol of key pests and minimise chemical inputs requires a much better understanding of pest and parasitoid taxonomy and biology throughout Europe. In Estonia, cropping with spring rape is still prevalent but growing of winter rape is also increasing. As Estonia is at the northernmost latitude for growing winter rape, winter survival of the crop is always questionable. The pests of oilseed rape and their natural enemies have been little studied in Esto- nia. The present study was focused on the identification of key pests and their parasitoids and determination of factors affecting their occurrence on both winter and spring oilseed rape. 7 1. REVIEW OF THE LITERATURE 1.1. Oilseed rape pests The major pests of oilseed rape in Europe are the pollen beetle, Meligethes aeneus (Fabricius) (Coleoptera, Nitidulidae), the cabbage seed weevil, Ceutorhynchus assimilis (Paykull), the cabbage stem weevil, C. pallidac- tylus (Marsham), the rape stem weevil, C. napi Gyllenhal (Coleoptera, Curculionidae), the cabbage stem flea beetle, Psylliodes chrysocephala (Linnaeus) (Coleoptera, Chrysomelidae) and the brassica pod midge, Dasineura brassicae (Winnertz) (Diptera, Cecidomyiidae) (Alford et al., 2003; Williams, 2004). Flea beetles (Phyllotreta spp., Coleoptera, Chry- somelidae) are also important, particularly on spring oilseed rape, the most frequent ones being P. nemorum (Linnaeus), P. atra (Fabricius), P. undulata (Kutschera) and P. nigripes (Fabricius). Some of these pests occur virtually everywhere where rape is grown, whereas others have a more limited distribution. None of these pests are specific to the oilseed rape crop, although all are crucifer-specialists. Many other crucifer-spe- cialist insects also occur on the crop, without attaining pest status (Alford et al., 2003). In Estonia, knowledge of the pests of oilseed rape is fragmentary and largely confined to the description of species. There was great shortage of literature about oilseed rape pest biology, abundance and the dam- age they cause. First data of oilseed rape pests and their control with pesticides date from Lõiveke (1991) and Kaarli (2000). More detailed descriptions of pests of brassicaceous crops are given by Metspalu & Hiie- saar (2002). With participating in the EU-funded project MASTER: MAnagement STrategies for European Rape pests, the Estonian Science Foundation Grant in 2002 and the project of Estonian Ministry of Agriculture in 2004, systematic studies of oilseed rape pests and investigations of fac- tors influencing their presence and abundance were started in the De- partment of Plant Protection of the Estonian University of Life Sciences. The aims of the MASTER project were to develop economically-viable and environmentally-acceptable crop management strategies for winter oilseed rape which maximise the biological control of key pests and min- 8 imise chemical inputs (Williams et al., 2002). Chemical control of pests of oilseed rape still prevails. Although insecticides can effectively control the pests, there is an urgent need to develop alternative strategies for managing