A Control Strategy for Tanytarsus Barbitarsis Freeman
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A CONTROL STRATEGY FOR TANY tarsus barbitarsis Freeman (Diptera: chironomidae) I A SMALL-SCALE PEST oRGANISM M.J. Kokkinn BSc (Hons) Department of ZoologY' The UniversitY of Adelaide A thesis submitted for the degree of Doctor of Phij-osoPhY December, 1986 At¡c,d¿d :sf ritr TABLE OF CONTENTS PAGE ]. SUMMARY DECLARATION 111 1V ACKNOWLEDGEMENTS 1. INTRODUCTION I 2. THE PHYSICAL ENVIRONMENT AND THE NATURE OF THE PROBLEM 9 3 ESTABL]SHING THE IDENTITY OF THE PROBLEM ORGANISM 20 Introduction 2A Materials and Methods 27 ResuLts 25 Discussion 36 4. POPULATION STUDIES 39 Introduction 79 I Pilot Survey 4T Materials and Methods 4L Resul-ts 42 Discussion 44 II The first year of sampJ-ing Q/7/82 to 7/7/87) 48 MateriaLs and Methods 48 a) Monitoring the physical environment 48 b) SamPJ-ing the biota 49 Resul-ts 51 a) The physical- environment 5l b) The biota 53 III The second year of sampling Q3/9/84 to 12/9/85) 64 Materials and Methods 64 a) lulonitoring the physical environment 64 b) SamPling the biota 64 Results 65 a) The PhYsical- environment 65 b) The biota 66 Discussion 74 TABLE OF CONTENTS (Continued) PAGE 87 5. FISH PREDATION Introduction 87 MateriaJ-s and Methods 89 I Feeding trials 89 II Gut contents 90 III Abundance of T. barbitarsis eggs 90 IV Fish excLusion exPeriments 91 ResuLts 94 I Feeding trials 94 II Gut contents 95 II] Abundance of T. barbitarsis eggs 95 IV Fish exclusion exPeriments 97 IO2 Di-scussion ]08 6. EGGS Introduction 108 Material-s ano Methods 110 I DescriPtive asPects 110 II lon excretion in eggs and embrYo rll III Egg hatching exPeriments II2 ResuLts u4 ï Descriptive asPects 1I4 I1 Ion exbretion in eggs and embrYo I20 III Egg hatching exPeriments L27 Discussion 126 176 7 OSMOREGULATION, SALINITY TOLERANCE AND ION EXCRETION Introduction L76 Materials and Methods r78 OsmoreguJ-ation 178 SalinitY toLerance I79 Sites of ion excretiorl 139 140 ResuLts Discussion 146 TABLE 0F CONTENTS (Continued) PAGE 8. ATTRACTION TO LIGHT 154 Introduction 154 Material-s Methods and Resul-ts r57 I Pilot survey I57 II Spectral preference experiments 161 Discussion 178 9. A VTRAL INFECTION 186 Introduction 186 MateriaLs and Methods I87 ResuLts 188 Discussion 188 ]0. GENERAL DISCUSSION 194 I Some possible controL strategies 194 II Further work 207 III The applicability of IPM to a small-scale pest 208 REFERENCES 2L4 i SUMMARY A control--orientated research programme was conducted on the chironomid, Tanytarsus barbitarsis Freemanr j-n the saline lagoons at port Augusta over a four year period. In this locality, adult flies are lrequently pestÍferous. The research had two main aims: i) to develop a stabi-e, Iong-term controJ- strategy which was environmental-ly sound; ii) to establ-ish whether it was possible to apply the philosophy of Integrated pest Management (IPM) to a smalL-scale pest organism through a biologicaL research programme of limited resources. The physical environment and the nature of the problem at Port Augusta are described. A morphoJ-ogical description of T . barbitarsis and T. semibarbitarsus heacl capsules Ís given which indicates that' although specimens of T. barbitarsis from Western Austral-ia and south eastern Austral-ia differ in their salinity tol-erance, they belong to the same morphospecies. A two-year population study shows T . barbitarsis to be muj-tÍvol-tine with the length of generati.on being temperature dependent. Observations indicate that predation on eggs and Lst instar larvae by juveniJ-e and l-arval fish (Atherinosoma microstoma) exercises natural controL on the T. barbitarsis population during spring and early summer Experimental excJ-usion of fÍsh gives support to the observations. The eggs of T. barbitarsis are highly impermeable until the pharate lst instar has deveJ.oped rectal- excretory tissue for osmoreguJ-ation. T. barbitarsis 4th instar larvae are abfe to ii osmoregulate in media between 5 and 15 g 1-1 NaCl; their LCro is l J-00 g I'r NaCI. Ion excretion is effected through the rectal tissue in larvae, but in pupae this site occurs on the dorsum of the thorax. Adul-ts are strongty attracted to two regj-ons of the electromagnetic spectrum, 490-5IOnm and 77}-400nm, the l-atter being more attractive. A pathogen with some potential- for control of T. barbitarsis is described as Tipul-a iridescent virus (TIV) ' An integrated control strategy using, fish predation, hypersaline _'l water (lOO g l--t) and }ight traps Ís proposed. A mathematical- modeL is used in a computer simulation to predict the resui-ts of control measures and the future nuisance outbreaks of T. barbitarsis adults at Port Augusta. The concept of IPM is discussed and the results of this research programme are evaluated: It is possible to derive control- strategies for small-scal-e pests through programmes of basic biological- research. I]-I DECLARATION This thesis contains no material which has been accepted for the awerd of any other degree or diploma in any University and, to the best of my knowledge and beliefr it contains no material previousl-y pubtished or written by anothel person except where due reference or acknowledgement i-s made. I give my consent to thls thesis beÍng made available for photocopying and loan. iv. ACKNOl/'lLEDGEMENTS The guidance, enthusiasm and sense of humour of Prof. lrl.D. Williams has made this thesis possible. The project was funded on grants from The Corporation of The City of port Augusta ancj The Electricity Trust of South AustraLia. I thank their l-iaison officers ¡4r R. Rutter and Dr R. Ainslie for their help and co-operation. The foll_owing staff in the Department of Zool-ogy at The University of Adelaide have given souncj advice and assistance: Mrs R. Evans - artwork; Mr P. Kempster - photography; Miss S. Lawson - editorial matters; Mr T. MacKenzi.e - apparatus; Mr D. Williams - logistics. Statistical- and mathematical- advice was given by: Mr T. Agnew' Ms J. Roberts, Dr W. VenabLes and Dr K. Walker' The computer model tvas written by Mr T. Agnew' Taxonomic advice and material was given by: Dr D. Edward' Mr B. Glover, Dr J. Martin and Dr P. Suter. Dr F. Jacka from The Mawson Institute advised me on matters pertaining to light and kindly all-oweO me to use his equipment. Mrs S. Thomas prepared tissue for TEM' Mr D. Peake-Jones assisted with coorong fish excl-osuIes. Friends and coLLeagues in The University of Adelaide Zoology Department helped by discussing ideas and reading drafts of written work. To all of the abovementioned, my sincere thanks are offered' Finally, I wish to thank Bev, David and Karmen for aLlowing me to take so many irreplaceable hours from them' þ 1 CHAP'IER 1 Introduction As part of the biosphere, man competes with a variety of organisms for finite lesources. The word tpestt is used to describe a certain group of organisms incl-uding competitors for food, libre and shelter, as weLl- as those which cause discomfort or iti- heal-th. Methods of combatting pests have reflected human cuLtural and technological deveJ-opment. Pre-agriculturaÌ (10,000 a B.P.) humans were nomadlc and tol-erated a variety of ectoparasites (l-ice, fl-eas and bugs), their only defence being personal- grooming (Southwood, L976). The development of agricultural- settlements led to the acquisition and culturaL transmission of pest control practices. Such practices were discovered by triat and error, and consequently they were often steeped in mystlcism and ritual (Philip and Rozeboom, L9T3). However, with the passage of time, the transition to rational pest control was made' The Chinese, for exampJ-e, understood the biology of many pest organisms and applied highly appropriate and ingenlous control- methods (Konishi and Ito, L977; Flint and Van den Bosch' 1981). Despite control measuresr pests, and particularJ-y insects, have had a profound infLuence upon human history, affecting the outcome of wars (for example, bubonic plague and mal-aria haJ-ted HannibaL at Syracuse) and causing mass human migrations (the IsraeLites from Egypt) (Howard, I93O; Cloudsley-Thompson, L976). The Renaissance in Europe led to a nelv emphasis upon scientific understanding. Entomology and especially systematic entomology were 2. initiated by Ulysse Aldrovandi Q522 - 1605 A.D.) (Beier, 1973). Accompanied by the growth in systematics and the deveJ-opment of the microscope by Leeuwenhoek QelZ - 1727), scientific investigation became the basis for pest control-. This ethic continued into the 20th century, cul-minating in the publication of E.D. Sandersonrs rlnsects of Farmt Garden ancj Orchard' (1915) which stressed the need for sound biological information and advocated the integration of a range of methods. In fact, the same approach (al-though not universalJ-y applied) is central- to current pest control phiJ-osophies, but a major diversion has intervened. During l^lorl-d l,rlar Ir (1940s), the threat to troops from insect-borne diseases (chlefly typhus borne by lice) prompted an intensive screening of chemical compounds for insecticidal activlty in the United States (PhiJ.ip and Rozeboom, 1973). The chl-orinated hydrocarbons, among them DDT (Oichloro-diphenyl-trichi-oroethane) - a compound first synthesized in 1874 and later discovered to have insecticidat activity by Meul-Ier in 1948 - were found to be highly effective. In response to the same problem, the organophosphates were discovered in wartime Germany. These discoveries gave impetus to a perception that chemicaLs were the most effective means of countering pests. Consequently, the post war yeaIs saw strong emphasis placed upon pesticides and by L962, a 2.3 X IOo kg of insecticide were being manufactured annuaJ-ly in the United States al-one (F1int and Van den Bosch' l98I).