___________________________________________________________________ Investigations on three species of Diptera associated with hawkweeds in Europe and their potential for biological control of alien invasive Hieracium spp. in New Zealand and North America ___________________________________________________________________ Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultät der Christian-Albrechts-Universität zu Kiel vorgelegt von Gitta Großkopf Kiel, März 2006 Referent/in: Prof. Dr. Hans Jürgen Braune Korreferent/in: Prof. Dr. Thomas Bauer Tag der mündlichen Prüfung: 27.4.2006 Zum Druck genehmigt: Kiel, ……………………………………………………….... Der Dekan Table of contents 1 General introduction................................................................................................................... 1 1.1 The taxonomy and distribution of Hieracium ........................................................................... 1 1.2 Hieracium pilosella and other hawkweeds as introduced invasive plants in New Zealand and North America................................................................................................................................ 2 1.3 Plant characters facilitating invasiveness: the morphology and ecology of mouse-ear hawkweed, H. pilosella .................................................................................................................. 3 1.4 Control methods for invasive hawkweeds ............................................................................... 4 1.5 Classical biological weed control............................................................................................. 5 1.6 The project for the biological control of hawkweeds in New Zealand and North America....... 8 1.7 Outline of this thesis .............................................................................................................. 10 2 Biology and life history of Cheilosia urbana (Meigen) and Cheilosia psilophthalma (Becker), two sympatric hoverflies approved for the biological control of hawkweeds (Hieracium spp.) in New Zealand................................................................................................ 12 2.1 Introduction............................................................................................................................. 12 2.2 Materials and Methods ........................................................................................................... 13 2.2.1 Adult emergence ............................................................................................................. 13 2.2.2 Longevity.......................................................................................................................... 14 2.2.3 Experiments to obtain mating in captivity........................................................................ 14 2.2.4 Release of marked females and field collection of gravid females................................. 14 2.2.5 Life span and fecundity of field-collected females .......................................................... 15 2.2.6 Egg morphology and development.................................................................................. 16 2.2.7 Phenology of C. urbana and C. psilophthalma................................................................ 16 2.2.8 Impact on H. pilosella ...................................................................................................... 17 2.2.9 Parasitoids....................................................................................................................... 18 2.3 Results ................................................................................................................................... 19 2.3.1 Adult emergence ............................................................................................................. 19 2.3.2 Longevity.......................................................................................................................... 19 2.3.3 Experiments to obtain mating in captivity........................................................................ 20 2.3.4 Release of marked females and field collection of gravid females................................. 20 2.3.5 Life span and fecundity of field-collected females .......................................................... 24 2.3.6 Egg morphology and development.................................................................................. 28 2.3.7 Phenology of C. urbana and C. psilophthalma................................................................ 29 2.3.8 Impact on H. pilosella ...................................................................................................... 30 2.3.9 Parasitoids....................................................................................................................... 33 2.4 Discussion ............................................................................................................................. 33 3 Host range of Cheilosia urbana and Cheilosia psilophthalma (Diptera: Syrphidae), candidates for the biological control of invasive alien hawkweeds in New Zealand.......... 37 3.1 Introduction............................................................................................................................. 37 3.2 Materials and Methods ........................................................................................................... 38 3.2.1 General ............................................................................................................................ 38 3.2.2 No-choice larval transfer tests in Switzerland................................................................. 41 3.2.3 No-choice larval transfer tests in New Zealand............................................................... 42 3.2.4 Single-choice oviposition tests in Switzerland ................................................................ 42 3.2.5 Open-field tests in Switzerland ....................................................................................... 43 3.3 Results ................................................................................................................................... 44 3.3.1 No-choice larval transfer tests in Switzerland................................................................. 44 3.3.2 No-choice larval transfer tests in New Zealand............................................................... 45 3.3.3 Single-choice oviposition tests in Switzerland ................................................................ 45 3.3.4 Open-field tests in Switzerland ....................................................................................... 50 3.4 Discussion ............................................................................................................................. 51 3.4.1 Estimating physiological host range................................................................................ 51 3.4.2 Predicting field host range and conclusions ................................................................... 51 4 Life history and host-specificity of Macrolabis pilosellae, a biological control agent of hawkweeds in the subgenus Pilosella in New Zealand ........................................................... 55 4.1 Introduction............................................................................................................................. 55 4.2 Materials and Methods ........................................................................................................... 58 4.2.1 Life cycle and phenology ................................................................................................. 58 4.2.2 Dissection of field-collected galls .................................................................................... 59 4.2.3 Longevity and fecundity of egg-laying females................................................................ 59 4.2.4 Mortality factors ............................................................................................................... 60 4.2.5 Host range investigations ................................................................................................ 60 4.3 Results ................................................................................................................................... 62 4.3.1 Life cycle and phenology ................................................................................................. 62 4.3.2 Dissection of field-collected galls .................................................................................... 66 4.3.3 Longevity and fecundity of egg-laying females................................................................ 68 4.3.4 Mortality factors ............................................................................................................... 69 4.3.5 Host range investigations ................................................................................................ 70 4.4 Discussion ............................................................................................................................. 75 5 The impact of Macrolabis pilosellae herbivory on plant parameters of mouse-ear hawkweed...................................................................................................................................... 78 5.1 Introduction............................................................................................................................