Effects of Temperature and Other Abiotic and Biotic Factors on Development and Survival of the Immature Stages of the Alfalfa Le

AN ABSTRACT OF THE THESIS OF Jaime M. Undurraga O. for the degree of Doctor of Philosophy in ENTOMOLOGY presented on June 9, 1978 Title: EFFECTS OF TEMPERATURE AND OTHER ABIOTIC AND BIOTIC FACTORS ON DEVELOPMENT AND SURVIVAL OF THE IMMATURE STAGES OF THE ALFALFA LEAFCUTTING BEE, MEGACHILE PACIFICA (PANZER) (= ROTUNDATA(F.)) (HYMENOPTERA: MEGACHILIDAE) Redactedfor Privacy Abstract approved: William P. Stephen Li` Larval mortality of leafcutting bee, Megachile pacifica(Panzer) (= rotundata (F.)), is high, usually exceeding 50%. Parasites and predators are not a limiting factor in the survival of the progeny. The disease chalk brood has been an important mortalityfactor since 1974. Inadequate food supply, pollen and nectar, may affect thesurvi- val of the progeny. Genetic differences within and between populations and the saponin content of alfalfa leaves do not affectbrood production or survival. Domicile design and protection may also have a great influence on survival. Temperatures exceeding 50°C occur in cells when nestingmaterial receives direct sunlight or when nesting material ishoused in domiciles with poor ventilation and insulation. There are temperature differences between cells in a series, between nestpositions within a domicile, and between types of nesting materials. There is no direct relationship between ambient and cell temperaturesbecause the latter are influenced by exposure,nesting media, placement, and domicile structure. High internal bee body temperatures may occurduring most bee activities, excluding resting. The effects of high temperatures on the adult bee or the eggs she contains are notknown. Although larval development canproceed at temperatures below21°C, survival is reduced. Adult activity, like metabolic larvaldevelopment, can be conditioned to unusually high or low temperatures;thus, there is no absolute temperature threshold for development or activity in this bee. Eggs and young larvae reared at a constant30°C hadover 85% survival, in most years. An ambient temperature of 45°C applied for one to three hours resulted in a higher mortality of eggsand early instars than the control temperature of30°C; at 50°C, mortality was complete. Exceptions were obtained for either situation. Half hour exposure at 50°C ambient temperature was also detrimental to immatures. An ambient temperature of 40°C in general does not affect survival of immatures. In-cell temperatures were at least 5°C lower than ambient temperatures in incubators during treatments. Repeating heat treatments on two or more days was not as severe as the duration of treatments. Larvae showed heat tolerance when exposed to two to three hours at45°C but not to one hour, but some exceptions occurred. The mechanism for heat tolerance is not well understood, and may be related to a conditioning of individuals tohigh temperatures. A seasonal effect on survival was obtained and appears not to be related to the age of the laying females, nor to the generations, but rather to the thermal history to which the immatures were exposed. Heat susceptibility of eggs and early instars seemed to be similar. Fourth and fifth instars were the most heat tolerant of alllarval stages. Exposure of young larvae to low temperatures before they were exposed to high temperatures did not increase mortality. However, sub- lethal high temperatures were generally less harmful tothe immatures that were conditioned but this acclimation of the larvaedid not occur in every test. Upper threshold temperature limits cannot beprecisely defined, nevertheless, cell temperatures over40°C result in egg and larval mortality. Brief exposure to45°C was the upper limit that developing pupae could tolerate;50°Cwas lethal. Pupae were most heat sensitive between three and six days before emergence. When exposed to high temperatures, pupae and emerging adults wereable to arrest development. Pupae and emerging adults can be conditioned totolerate short exposures to lethal temperatures up to seven days before emergence. Low temperatures did not affect the survival of pupae. Development of pupae and emerging adults could be arrested for up to a week at15.6°C without harmful effect. Development and emergence proceed at 21 °C, but pupae need at least 2.5 hours per day of temperatures above 21°C to survive when not in an arrested state. Pupae not exposed to temperature above 29°C during 24 hours, emerged normally. Incubation at 29.5°C for less than 10 hours per day delayed the emergence. Pupae maintained at 15.6 °C for 22 hours per day for 8 days or for 20 hours per day for 16 days emerged after adelay longer than the period of cold. Cooling the emerging bees after high temperature treatment appeared to be more detrimental than cooling before exposures to high temperatures. The detrimental effect of extreme temperatures was shown on the survival of eggs, young larvae,and pupae, but possible chronic effects on later stadia were not studied. Effects of Temperature and other Abiotic and Biotic Factors on Development and Survival of the Immature Stages of the Alfalfa Leafcutting Bee, Megachile pacifica (Panzer) (= rotundata (F.)) (Hymenoptera: Megachilidae) by Jaime M. Undurraga 0. A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Completed June 9, 1978 Commencement June 1979 APPROVED: Redacted for Privacy Professor of Entomology in chargeofiajor Redacted for Privacy Head of Department of Entomology a- Redacted for Privacy Dean of Graduate School Date thesis is presented June 9, 1978 Typed by Joyce E. McEwen for Jaime M. Undurraga 0. To my wife, Maria Teresa, parents, brothers, and sisters. ACKNOWLEDGEMENTS I want to express my deep and sincere appreciation to my major professor, Dr. William P. Stephen, for his continuous encouragement and assistance during the years of work on this dissertation. Without his patient understanding, friendly advice, helpful suggestions, construc- tive criticism, and wisdom this research would have been exceedingly difficult. I am grateful to the members of my committee, Drs. N.H. Anderson, R.E. Berry, D.F. Grabe, C.M. Leach, and C.D. McIntire for their guid- ance and valuable suggestions, and to Drs. W.P.Nagel and R.B. Roberts, former members of my committee, for their encouragement and helpful comments. I am indebted to Dr. K. Rowe for the development of statistical methods of analysis of the data in this thesis, and to Dr. J.D. Lattin, for his encouragement and financial support, while Acting Head ofthe Department of Entomology. My sincere and special thanks are expressed to Dr. L.C. Ryker who helped and provided me with valuable suggestionsthroughout these years. Special recognition goes to Mr. D. Gehring, former Technician, for his cooperation and help in gathering some of thedata. I wish to thank Dr. D.M. Burgett for his moral andfinancial assistance, and Dr. G. Fisher, for encouraging me tocomplete the thesis while working on the Alfalfa Seed Pest ManagementProgram. I also thank Mr. N. Hoffman, former Superintendent,for providing me facilities at the Malheur Exp.Sta., Ontario, Oregon, and to Dr. N. Waters and Dr. W. Kochan for the loanof equipment from the Parma Exp. Sta., University of Idaho. My thanks are expressed to Mr. Ted Avery,John Dority, William Panike, Darrell Panike, George Schiemer, Robert Ureand Van Ure, of Malheur County, for their help, support, andfacilities provided throughout the development of this dissertation. I am grateful to the Idaho AlfalfaSeed Commission and the Field Seed Institute of North America for providingfinancial support for part of this research. I also aCknowledge the Organizationof American States for a fellowship during part of the period of these studies. I acknowledge the assistance and encouragement and express my sincere appreciation to all my professors, fellow students, and friends, who have helped me during my studies at Oregon State University. Lastly, I am indebted to my wife, Maria Teresa, for her patient encouragement and loveliness during the preparation of this thesis. Jaime Undurraga 0. TABLE OF CONTENTS Page. I. INTRODUCTION 1 II. SURVEY OF MORTALITY FACTORS 8 2.1 Early Mortality 8 2.2 Parasites and Predators 11 2.3 Diseases 15 2.4 Lack of Pollen and Nectar 16 2.5 Effect of Geographical Localities on 19 Cell Production and Mortality 23 2.6 Leafcutting Bee Cell Composition 2.6.1 Quality of cell leaves 23 2.6.2 Quantity of cell leaves 26 28 2.7 Mortality as a Function of Domiciles 37 III. TEMPERATURE AS A MORTALITY FACTOR 37 3.1 Introduction 38 3.2 Ambient Temperatures Found in Eastern Oregon 38 3.3 Temperature in Nests and Domiciles 49 3.4 Bee Body Temperature 55 3.5 Early Larval Mortality Associated with Low Temperatures 58 IV. EFFECT OF HIGH TEMPERATURES(400-50°C) ON THE SURVIVAL OF EGGS AND EARLY INSTARS OF LEAFCUTTING BEES 58 4.1 Introduction 58 4.2 1973 Materials and Methods 60 4.2 1973 Results and Discussion 64 4.3 1974 Materials and Methods 66 4.3 1974 Results and Discussion 80 4.4 1975-76 Materials and Methods 81 4.4 1975-76 Results and Discussion 95 4.5 Larval Age and Temperature Tolerance 4.5.1 1975 Materials and Methods 95 97 4.5.2 1975 Results and Discussion 105 4.6 1976 Materials and Methods 106 4.6 1976 Results and Discussion 106 4.7 Effect of Age on Heat Tolerance 4.7.1 1976 Materials and Methods 106 4.7.2 1976 Results and Discussion 108 110 4.8 Effect of Pretreatments before Exposureto High Temperatures 110 4.8.1 1976 Materials and Methods TABLE OF CONTENTS (Cont.) Page 4.8.2 1976 Results and Discussion 110 4.9 Effect of Conditioning of Immatures to 112 High Temperatures 4.9.1 1976 Materials and Methods 112 4.9.2 1976 Results and Discussion 113 4.10Effect of Conditioning of In-Cell Temperatures 113 of 50°C on Survival 4.10.1 1976 Materials and Methods 113 4.10.2 1976 Results and Discussion 115 V.

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