DIPTERA: CECIDOMYIIDAE) in RESPONSE to Llmlted AVAILABILITY of ITS PREY Tetranychus Urticae KOCH (ACARI: TETRANYCHIDAE)
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LARVAL DEVELOPMENT OF THE PREDATORY MIDGE Feitieila acarisuga VALLOT (DIPTERA: CECIDOMYIIDAE) IN RESPONSE TO LlMlTED AVAILABILITY OF ITS PREY Tetranychus urticae KOCH (ACARI: TETRANYCHIDAE) by Heidi Nadene Sawyer Mc., University of British Columbia, 1991. THESIS SUBMllTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PEST MANAGEMENT in the Department of Biological Sciences O H.N. Sawyer 1998 SIMON FRASER UNIVERSITY January 1998 All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other rneans, without permission of the author. Bibliothèque nationale du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Çtreet 395. rue Wellington Ottawa ON KIA ON4 OttawaON KlAûN4 CaMdct canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Lhrary of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sen reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/^ de reproduction sur papier ou sur fonnat électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or othenivise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ABSTRACT In order to evaluate the predatory midge Feltiella acarisuga Vallot as a biological control agent for the two-spotted spider mite Tetranychus uttïcae Koch (TSSM) in greenhouses, information is needed on its performance under conditions of prey limitation. To study the effects of chronic low prey density, larvae were provided with 4 different feeding treatments of 60 (approximately the maximum daily consumption) 30, 15, or 5 TSSM eggs per day. Larval survival was significantly affected by prey availability with no lawae surviving to pupation when provided 5 eggs per day. Among the groups with surviving larvae, reduction in prey availability caused significant decreases in the total mite-egg consumption and the dry weight at pupation. Pupal weight was a linear function of the total number of eggs eaten. To study the effects of short-tenn deprivation, larvae were first provided with either 60 eggs per day (well-fed) or 15 eggs per day (poorly-fed). After two days of feeding, larvae were kept without prey for 0,1,2,4 or 6 days and then re-fed at the previous rate. A proportion of larvae resumed feeding and reached pupation after al1 deprivation periods, but survival decreased with deprivation time among both well-fed and poorly-fed larvae to a minimum of approximately 30%. Developmental the increased significantly with increasing deprivation time and was also significantly longer in the poorly-fed larvae compared to well- fed larvae. Total lifetime egg consumption and pupal dry weight were both significantly reduced by deprivation among well-fed larvae but not among poorly-fed larvae. Among the well-fed larvae, pupal weight and egg consumption were significantly reduced by shorter deprivation times of one and two days, but were unaffected by longer deprivation times of four and six days. These results appeared to have been influenced by behavioral changes during deprivation. Lawae were very active after one or two days deprivation but became sedentary at four, five and six days without prey. Daily feeding capacity was also reduced after four or six days deprivation. Despite differing periods of deprivation, al1 well-fed larvae consistently consumed more eggs than poorly-fed larvae and achieved higher pupal weights. ACKNOWLEDGMENTS I am very grateful to my senior supervisor Dr. Bemie Roitberg for his direction and support during this study. I would also like to thank Dr. Dave Gillespie and Dr. Ron Ydenberg for valued advice and editing, Nature's Alternative lnsectary and Dr. Dave Gillespie for providing the insects, Ed Basalyga for collaboration in the experirnent in chapter 2, and Cynthia Feil and Sue Robertson for technical assistance. Thanks also go to the mernbers of the Roitberg lab, MPM students, and my farnily and friends who have helped and encouraged me. Financial assistance was provided by the Western Greenhouse Growers Cooperative Association, Agriculture and Agri-Foods Canada, an NSERC grant to Dr. B. Roitberg and by several Teaching Assistantships at Simon Fraser University. Statistical advice was provided by Robert Balshaw and lan Bercovitz of the Statistical Consulting Group, Simon Fraser University. TABLE OF CONTENTS .. APPROVAL.................................................................................................................. II m.. ABSTRACT.. ......................................................................................................... ..r II ACKNOWLEDGMENTS.. .......................................................................................... ..iv TABLE OF CONTENTS ...............................................................................................v LIST OF TABLES ........................................................................................................vi *. LIST OF FIGURES..................................................................................................... VII 1. INTRODUCTION..................................................................................................... 1 2. EFFECTS OF CHRONIC LOW MITE DENSITY ON PREY CONSUMPTION, SURVIVAL AND DEVELOPMENT OF F. ACARlSUGA A. Introduction................................................................................................. 1 O B. Materials and Methods i) Plant, Mite, and Insect Colonies.......................... ..... ...................... 13 ii) Experimental Arenas for F. acarisuga larvae ...................................14 iii) Experimental Procedures and Analyses .......................................... 15 C. Results.. ......................................................................................................17 D. Discussion............................................................................................... 1 9 3. EFFECTS OF TEMPORARY DEPRIVATION ON PREY CONSUMPTION, DEVELOPMENT, SURVIVAL, AND ACTIVITY OF F. ACARlSUGA LARVAE A. Introduction................................................................................................ .25 B. Materials and Methods................................................................................ 28 C. Results....................................................................................................... .31 D. Discussion. ..................................................................................................33 4. CONCLUSIONS .....................................................................................................41 REFERENCES.......................................................................................................... .64 LIST OF TABLES Table 1. Cornparison of pupation in F. acarisuga la~aereared with four different densities of T. urficae eggs. At the lowest density of 5 eggs per day, approxirnately half the larvae went missing and were presumed to have escaped, and none of the remaining lawae reached pupation............................................ 45 Table 2. The means and standard deviations of the daily number of eggs of T. urticae eaten by larvae of F. acarisuga during the first four days of feeding at three different densities of eggs ........................................................................... 46 LIST OF FIGURES Figure 1. A diagram of experimental arenas used to enclose and observe larvae of F. acarisuga. a) petri dish filled with agar b) hole cut out of agar c) plastic coverslip............................................................................................................... 47 Figure 2. Number of F.acarisuga larvae reaching pupation on each day after eclosion, while feeding at three different prey densities. Larvae were reared in agar cells with 60, 30, or 15 eggs of T. urticae per day. Symbols V indicate the mean developmental times for each treatment .....................................................48 Figure 3. Mean number of T. urticae eggs consumed by F. acarisuga during the entire larval period at three different prey densities. Error bars indicate 95% confidence intervals.............................................................................................. 50 Figure 4. Mean pupal dry weights of F. acarisuga after feeding at three different densities of T. urticae eggs. Error bars indicate 95% confidence intervals......... 51 Figure 5. The relationship between the total number of T. urticae eggs consumed by F. acarisuga larvae, and the dry weight of F. acarisuga at pupation. Data from larvae fed at al1 three prey densities are included. The regression equation for the line is Y = 0.21 x - 2.28 (t= 0.91).................................................................. 52 Figure 6. The relationship between the developmental time of F. acarisuga and the dry weight at pupation. Data from larvae provided with three different prey densities are included. Larvae feeding at the highest density had greater vii variation in pupal weight, whereas those feeding at the lowest density had greater . variation