Aus dem Zoologischen Institut -Zoophysiologie- Studies on the ecology of European Peristenus spp. (Hymenoptera: Braconidae) and their potential for the biological control of Lygus spp. (Hemiptera: Miridae) in Canada Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultät der Christian-Albrechts-Universität zu Kiel vorgelegt von Tim Haye Kiel, Mai 2004 Table of contents 1 General Introduction.............................................................................. 1 1.1 Biology and pest status of Lygus plant bugs in Canada...................................... 1 1.2 Classical biological control of insects .................................................................. 3 1.3 Risk assessment in biological control .................................................................. 4 1.4 Current control methods for Lygus spp. in Canada ........................................... 5 1.5 Thesis outline ....................................................................................................... 7 2 Seasonal occurrence of Lygus spp. (Hemiptera: Miridae) and parasitization of their nymphs by Peristenus spp. (Hymenoptera: Braconidae) in Schleswig-Holstein (Germany)..................................... 9 2.1 Introduction ......................................................................................................... 9 2.2 Material and methods........................................................................................ 10 2.2.1 Study area and field sites .................................................................................. 10 2.2.2 Sampling methods ............................................................................................ 12 2.2.3 Determination of parasitization level and parasitoid species composition.......... 13 2.2.4 Rearing............................................................................................................. 13 2.2.5 Overwintering................................................................................................... 15 2.2.6 Monitoring of parasitoid emergence.................................................................. 15 2.2.7 Data analysis .................................................................................................... 16 2.3 Results ................................................................................................................ 16 2.3.1 Seasonal occurrence of Lygus rugulipennis in clover and camomile.................. 16 2.3.2 Parasitization level of L. rugulipennis nymphs in clover and camomile............. 19 2.3.3 Parasitoid species composition.......................................................................... 21 2.3.4 Emergence pattern of Lygus parasitoids under laboratory and natural temperature conditions ......................................................................................................... 27 2.3.5 Nymphal parasitoids of Lygus pratensis L. ....................................................... 31 2.3.6 Nymphal parasitoids of Lygus maritimus Wagner ............................................. 32 2.4 Discussion........................................................................................................... 32 2.4.1 Seasonal occurrence of Lygus rugulipennis....................................................... 32 2.4.2 Nymphal parasitization of Lygus rugulipennis .................................................. 33 2.4.3 Parasitoid species composition.......................................................................... 36 2.4.4 Parasitoid emergence ........................................................................................ 38 2.4.5 Nymphal parasitoids of Lygus pratensis and L. maritimus................................. 40 2.4.6 Consequences for biological control ................................................................. 40 3 Physiological host range of Peristenus digoneutis and P. stygicus (Hymenoptera: Braconidae), parasitoids of Lygus spp. ..................... 44 3.1 Introduction ....................................................................................................... 44 3.2 Material and methods........................................................................................ 45 I 3.2.1 Source of parasitoids and nymphs..................................................................... 46 3.2.2 Sequential non-choice tests............................................................................... 47 3.2.3 Simultaneous choice tests ................................................................................. 50 3.3 Results ................................................................................................................ 51 3.3.1 Parasitoid oviposition behavior......................................................................... 51 3.3.2 Sequential non-choice tests............................................................................... 51 3.3.3 Simultaneous choice tests ................................................................................. 55 3.4 Discussion........................................................................................................... 57 3.4.1 Host specificity with regard to the experimental design..................................... 57 3.4.2 Consequences for biological control ................................................................. 61 4 Ecological host range of Peristenus digoneutis and P. stygicus (Hymenoptera: Braconidae) in Schleswig-Holstein............................62 4.1 Introduction ....................................................................................................... 62 4.2 Material and methods........................................................................................ 63 4.2.1 Sampling .......................................................................................................... 63 4.2.2 Rearing, overwintering and parasitoid emergence ............................................. 64 4.2.3 Estimating the impact of Lygus parasitoids on non-target mirids ....................... 65 4.3 Results ................................................................................................................ 66 4.3.1 Records of mirid species in Schleswig-Holstein................................................ 66 4.3.2 Ecological host range of P. digoneutis and P. stygicus ...................................... 67 4.3.3 Ecological host range of further nymphal parasitoids of mirids ......................... 69 4.3.4 Proportions of P. stygicus and P. digoneutis emerging from non-target mirids .. 70 4.3.5 Impact of P. stygicus and P. digoneutis on non-target mirids at single collection sites .................................................................................................................. 74 4.3.6 Simultaneous collections of Lygus and non-target hosts.................................... 74 4.3.7 Occurrence of mirid plant bugs and emergence pattern of their associated parasitoids under natural temperature conditions............................................... 76 4.4 Discussion........................................................................................................... 77 4.4.1 Ecological host range of P. digoneutis and P. stygicus ...................................... 77 4.4.2 Parasitoid associations of other mirids .............................................................. 84 4.4.3 Consequences for biological control ................................................................. 85 5 Reproductive biology of Peristenus digoneutis and P. stygicus (Hymenoptera: Braconidae), parasitoids of Lygus spp. ..................... 88 5.1 Introduction ....................................................................................................... 88 5.2 Material and methods........................................................................................ 89 5.2.1 Timing of egg production in adult parasitoids ................................................... 89 5.2.2 Source of hosts and parasitoids ......................................................................... 91 5.3 Results ................................................................................................................ 92 5.3.1 Timing of egg production in parasitoid adults ................................................... 92 5.3.2 Age-specific fecundity...................................................................................... 92 5.3.3 Potential lifetime fecundity............................................................................... 94 II 5.3.4 Level of parasitization and self-superparasitization........................................... 94 5.3.5 Adult longevity................................................................................................. 96 5.3.6 Relationship between lifetime fecundity and body size, longevity, and oviposition period ............................................................................................................... 96 5.4 Discussion........................................................................................................... 98 5.4.1 Reproductive biology of Peristenus spp. ........................................................... 98 5.4.2 Consequences for biological control ............................................................... 103 6 Cold-hardiness of Peristenus digoneutis and P. stygicus (Hymenoptera: Braconidae) .............................................................