Introduction of Aphídíus rosae into Australia for Biological Control of the Rose Aphid (Macrosiphum rosae) By Jörg Thomas Kitt Diplom Biologe, Technische Universität Hannover A thesis submitted for the Degree of Doctor of Philosophy in the Faculty of Agricultural and Natural Resource Sciences at the University of Adelaide Department of Crop Protection The University of Adelaide Mehr und mehr mußte er Abschied nehmen vom Traum, von dem GefÍihl und Genuß der unendlichen Möglichkeiten, der tausendf?iltigen Zukunft ... ... stattdessen eine kleine, fordernde Wirklichkeit. H. Hesse (Glasperlenspiel) Declaration This work contains no material which has been accepted for the award of any other degree or diploma in any university or other tertiary institution and, to the best of my knowledge and belief, contains no material previously published or written by another person, except where reference has been made in the text. This thesis may be made available for loan or photocopying provided that an acknowledgment is made in instance of any reference to this work. Jörg Kitt, January 1996 I TO MY PARENTS AND FAMILY l1 Acknowledgment I would like to thank all those who contributed to the completion of my thesis. It is due to Denek Maelzer that this project ever started. His experience in the biology of rose aphids and his wisdom in insect ecology were an invaluable source of knowledge before his retirement. Essential contribution to this project was made by Cristina Degilo who helped me with the insect collection in Italy. I am very thankful for the hetpful discussions with Peter Miles, Roger Laughlin, Rick Roush, Peter Bailey and Mary Carver. My dear fellow postgraduates did always inspire me in our countless conversations. I am very grateful to Bill de Frost, Lynne Grbin, Scott Field, Chris Madden, Paul Dangerfield, Nicky Agelopoulos and Francis Fitzcibbon. All of them looked also kindly after my insect cultures during my periods of absence. Thanks to Ebrahim Soleyman, Bijan Hatami, Latif Salehi, Steve Ball and Brigitte Tenhumberg for making the office a pleasant place to work. The help from my supervisor Mike Keller was priceless. He especially gave me always support in critical moments and my discussions with him about parasitoid ecology broadened my horizon. His statistical advises contributed essentially to this thesis. I am very grateful for the honour to meet the late Dean Ross, a man who always believed in my project and encouraged me to keep going. After his sudden death, his wife Maureen and the whole management from Ross Roses nursery kept supporting me enthusiastically. During my studies I was supported by an University of Adelaide Scholarship. Most of all I would like to thank Catherine for her patience and the amount of work she had to take over from me in the upbringing of our daughter Sophie. lll TABLE OF CONTENTS Page DECLARATION I ACKNOWLEDGMENT ur TABLE OF CONTENTS lv SUMMARY vl CHAPTER 1. INTRODUCTION TO TIIESIS. 1 CHAPTER 2. PRELIIVIINARY CONSIDERATION OF A. ROSA^E AS 4 CONTROL AGENT OT M. ROSAB. CHAPTER 3. FIELD COLLECTION AND REARING OFA. ROSAE. 18 CHAPTER 4. INFLUENCE OF HOST QUALTTY ONA. ROSAE. 34 CHAPTER 5. FECUNDITY AND INTRINSIC RATE OF INCREASE 68 OF,A. ROSAE AND M. ROSAE, CHAPTER 6. HOST SELECTION OF A. ROSAE WITH RESPBCT 89 TO ASSESSMENT OF HOST SPECIFICITY IN BIOLOGICAL CONTROL. CHAPTER 7. INTRA.PATCH FORAGING OF A. ROSAE 102 CHAPTER 8. NUMBER RELEASED AND SUCCESS IN tt2 ESTABLISIIMENT OF A. ROSAE IN VICTORIA. CHAPTER 9. ESTABLISHMENT AND SPREAD OF A. ROSAE IN 122 ADELAIDE. lV Page CHAPTER 10. THE CHANGES OF NUMBERS OF A. ROSAE ANT) 136 M. ROSAE IN THE FIELD. CHAPTER 11. EXPERIMENTAL APPROACH TO ASSESS THE t92 IMPACT OFA. ROSAE IN THE FIELD. CHAPTER 12. CONCLUSION 217 REFERENCES 221 APPENDICES 240 V Summary Macrosiphum rosae (L.) was introduced into Australia as a result of European settlement and can be considered the most serious insect pest of roses. Some native predators feed on M. rosae, but an effective parasitoid guild of this aphid was missing in Australia. The most promising control agent Aphidius rosae was introduced into South- Eastern Australia to improve biological control of rose aphids. To improve rearing conditions and to gain a better understanding of the performance of A. rosae in the field, investigation of some parameters of life-history were undertaken. V/ith increasing instar at time of parasitization, aphids became more suitable for parasitoid growth, with an overall increase in parasitoid size and fecundity from Ll to L4 and a decrease in developmental time. Host quality was dependent on aphid instar at time of parasitization. Poor plant quality and hyperparasitism had a negative effect on parasitoid growth. It can be concluded that growth of A. rosae was greatly susceptible to changes in nutritional quality of its host. A. rosae was able to exploit the whole range of instars and adults. The sex-ratio was male-biased in less suitable hosts. Life-time fecundity increased with parasitoid size. The net life-time fecundity ranged between 144 and 790 at 18"C and increased with the size of females. The intrinsic rate of increase of A. rosae ranged from 0.258 ¡o 0.323 females/female/day, compared to an average intrinsic rate of 0.319 for M. rosae. Discrete steps in the process of host selection were studied to assess the host specificity of A. rosae. In a wind tunnel, females were strongly attracted only to roses when given a choice between uninfested roses and other plants. In a two-choice test females were not able to distinguish between aphid-infested rose shoots and uninfested rose shoots when shoots were 30 cm apart but they preferred to land on infested buds VI when shoots were only 5 to l0 cm apart. Results suggest that aphid-related volatiles involved in host location are detectable by the wasp only over a short distance. A range of aphid species was exposed to A. rosae in choice and no-choice conditions in petri- dishes. The only aphid species parasitized, other than M. rosae, was Macrosiphum euphorbiae Thomas but oviposition did not result in offspring. A. rosae was considered specific to the rose aphid under given circumstances in Australia and negative environmental impacts were considered as almost non-existent. Initial field observations were carried out to obtain a basic impression of the foraging behaviour of. A. rosae in a patch. The wasps displayed significant differences in their activities when observations in the morning were compared with observations in the afternoon. A. rosae females showed higher attack rates in the morning compared to individuals observed in the afternoon. Parasitoids attacked only the edges of aphid colonies. A. rosae established in most places released. At the release site in Adelaide, South Australia, the spread of a small population of parasitoids was monitored monthly. Seven months after the first release A. rosae inhabited an area of approximately 200 km2 and was found as far as 18 km away from the nearest release site. The density of mummies decreased with increased distance from the point of release, but the spread was not random. Parasitoids spread mainly in the direction of prevailing winds. The release of. A. rosae was used to test the hypothesis that a threshold of about 1000 insects released at a single site and time is needed for establishment. 16, &,256 and lO24 mummies of A. rosae were released in eight cities throughout Victoria. Six months after release, recoveries were made in three sites in where 64,256 and lO24 mummies were released. After one year, mummies were found even at a place where only 16 mummies were released. Over a period of two years after initial release, the changes in numbers of host and parasitoid were monitored in a rose freld. Before the release of A. rosae, spring was vii the season when M. rosae was most abundant as have been recorded previously. After the release, M. rosae did not reach the same high infestations levels as have been recorded previously in spring. High rates of parasitism of nearly 8O Vo in spring suggested that A. rosae may have been the main natural enemy in regulating aphid numbers. During summer M. rosae and A. rosae virtually disappeared from roses in Adelaide. During autumn aphids reached high numbers and A. rosae did not have any significant impact on its host. This ineffectiveness of A. rosae in autumn was also demonstrated in an experiment using insecticide-treated exclusion cages. No signif,rcant change in aphid numbers was found when natural enemies were excluded from roses. Aphid infestations sampled in different rose plots varied considerably when wider surveys were undertaken. viii t) ,S'¿il ¡i Introduction to thesis The rose aphid Macrosiphum rosae (L.) is the most serious pest of roses in South Australia. Up to 1993, nurseries and home gardeners depended exclusively on insecticides to control this introduced pest, since native predators did not regulate numbers of rose aphids. In Europe, America and Eurasia, populations of M. rosae are attacked by a number of parasitoid species. The most common species is the Aphidiinae wasp Aphidius rosae Haliday. This thesis deals with the introduction of A. rosae as a classical biological control agent into South-Eastem Australia. Aims. The ultimate aim of this project was to establish A. rosae in South-Eastern Australia to improve biological control of the target pesr. M. rosae. Appropriate host specificity tests had to be carried out to ensure environmental safety of the control agent and to achieve clearance for release into the field from the Australian Quarantine and Inspection Service and the National Park and lVildlife Service. Except for host references, little was known on the biology of A.