FIELD ENHANCEMENT OF THE PARASITOID Bracon hylobii (Hymenoptera: Braconidae) TO CONTROL Hylobius abietis (Coleoptera: Curculionidae); THE LARGE PINE WEEVIL. Michael G. Moran (B. Agr. Sc. (Forestry)) A thesis submitted in fulfilment of the requirements of HETAC for the degree of Doctor of Philosophy Galway-Mayo Institute of Technology Supervisor: Dr Patrick Walsh Submitted to the Higher Education and Training Awards Council March 2012 Declaration I declare that this thesis, in whole or in part, has not been submitted to any University as an exercise for a degree. I hereby certify that this material is entirely my own work and has not been taken from the work of others save and to the extent that such work has been cited and acknowledged within the text of my work. The author agrees that the library may lend or copy the thesis upon request for study purposes, subject to the normal conditions of acknowledgement. Signed: c Candidate: Supervisor: Date; FIELD ENHANCEMENT OF THE PARASITOID Bracon hylobii (Hymenoptera: Braconidae) TO CONTROL Hylobius abietis (Coleoptera: Curculionidae); THE LARGE PINE WEEVIL. Michael G. Moran ABSTRACT Hylobius abietis (Coleoptera: Curculionidae), the large pine weevil is the most damaging pest of reforestation sites in Ireland. This study examined the possibility of manipulating populations of a species specific parasitoid, Bracon hylobii (Hymenoptera: Braconidae) to reduce weevil populations below damaging levels or to a level where they may be of use in an Integrated Pest Management system. Levels of parasitism were studied in the field on recently felled Sitka spruce and Lodgepole pine sites in an attempt to measure ‘natural’ rates of parasitism. Highest rates of parasitism measured were 42% and 21% on Lodgepole pine and Sitka spruce sites respectively. This was very much lower than required for control. Field studies of parasitoid emergence and laboratory trials indicated that two peaks of adult emergence occurred during the year. Synchronisation of peak emergence with the most vulnerable stage of the weevil is discussed. It may be that an ample portion of the H. abietis population survives to cause economic damage no matter how many parasitoids are on site due to overlapping of generations. Attempts to enhance the populations of the parasitoid in the field failed due to migration of the flying adults. Reasons for this were investigated through field surveys of available plant food (nectar) and laboratory choice chamber experiments. It was concluded that the need for food and possibly, mutual interference resulted in a net migration of adults from the sites in which they emerged from the cocoons. Experimentally it was demonstrated that the presence of food resulted in greater longevity and hence longer periods for searching and oviposition. The presence of flowering plants onsite may result in greater levels of parasitism. However, this is inconclusive. The possibility of a hyperparasitoid being present was investigated using mtDNA techniques. No evidence was found to indicate the presence of a hyperparasitoid. This study indicates that natural levels of parasitism in recently clearfelled Lodgepole pine and Sitka spruce forest sites is insufficient to control Hylobius abietis. The ability to enhance ‘natural’ populations by introducing laboratory reared populations failed because of the tendency of adult parasitoids to disperse. No hyperparasitoid is present. ACKNOWLEDGEMENTS I would like to thank the following people who have helped me in the completion of this research project: > Dr. Patrick Walsh for his persistence, supervision, guidance and commitment. > Martine Blaix for her help and organization skills. > The Forest Service through Coford for funding this research project. > Project partners from NUIM and Coillte, for their advice, recommendations and support. > Karl Magnacca, Postdoctoral Researcher, Department of Zoology, Trinity College, for the DNA testing he carried out. > My colleagues for their advice and recommendations. > My family and friends for their motivation and support. > A special thanks to Aine for her endless help, support and patience. TABLE OF CONTENTS 1 General Introduction............. 1 1.1 The Problem .......................................................................................................1 1.2 Why is control by pesticides a problem?..............................................................2 1.3 Possible solutions................................................................................................4 1.4 Why control Hylobius Abietis?........................................................................... 4 1.4.1 Hylobius abietis History and life cycle......................................................... 5 1.5 Non chemical Control of Hylobius abietis.......................................................... 13 1.5.1 Physical barriers, Traps and Antifeedants....................................................13 1.5.2 Habitat/ breeding site manipulation.............................................................16 1.5.3 Silvicultural systems...................................................................................18 1.5.4 Biological control........................................................................................19 1.6 Methods of biological control............................................................................22 1.6 .1 Introductions.............................................................................................. 22 1.6.2 Augmentation............................................................................................. 22 1.6.3 Conservation.............................................................................................. 23 1.6.4 Factors affecting biological control methods............................ 24 1.7 Biological control measures against Hylobius abietis.........................................27 1.8 Parasitic wasps.................................................................................................. 30 1.8.1 Bracon hylobii history and life cycle..........................................................31 1.8.2 Morphology.................................................................................................33 1.8.3 Host location and oviposition...................................................................... 35 1.8.4 Emergence, Diapause and overwintering.....................................................39 1.8.5 Longevity and fecundity.............................................................................40 1.8.6 Patch exploitation and dispersion................................................................ 41 2 The obj ectives of this research proj ect..................................................................... 43 3 Bracon hylobii field emergence............................................................................... 44 3.1 Introduction.......................................................................................................44 3.2 Objective...........................................................................................................4 4 3.3 Materials and methods....................................................................................... 4 5 3.4 Results.............................................................................................................. 4 7 3.5 Discussion............................ 52 4 Attractiveness of Four commonly found Clearfell Floral plants to B. hylobii........... 57 4.1 Introduction............... 5 7 4.2 Objective.............................. 58 4.3 Material and Methods........................................................................................58 4.4 Results.............................................................................................................. 60 4.5 Discussion........................................................................................................ 62 5 Effect of larval food source (tree species) and non-host food on the searching behaviour of adult B. hylobii........................................................................................... 64 5.1 Introduction....................................................................................... *..............64 5.2 Objective...........................................................................................................65 5.3 Materials and methods................................................. 65 5.4 Results..................................................................................*.......................... 67 5.5 Discussion.........................................................................................................68 6 Effect of food quality and feeding frequency on the Longevity of B. Hylobii...........70 6.1 Introduction.......................................................................................................70 6.2 Objective...........................................................................................................71 6.3 Materials and methods .................................................................. ......... 71 6.4 Results...............................................................................................................71 6.5 Discussion.................................................. 74 7 Parasitism rates of B. hylobii in field and laboratory conditions............................... 75 7.1 Introduction.......................................................................................................75