~ OIDAEMATOPHORUS MONODACTYLUS (L.) AND BEDELLIA SOMNULENTELLA (ZELLER): TWO POTENTIAL BIOLOGICAL CONTROL AGENTS OF HEDGE BINDWEED;IN SOUTHWESTERN VIRGINIA By Michael Peter,Parrellal/ J Thesis submitted to the Graduate Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in ENTOMOLOGY Approved: Dr. L. T. Kok, Chairman Dr. R. L. Pienkowski Dr. D. G. Cochran Dr. J. McD. Grayson May, 1977 Blacksburg, Virginia To My Parents- whos e encouragement and support made this possible ii ACKNOWLEDGEMENTS I would like to express my sincere appreciation to whose understanding, patience and guidance aided immeasurably in the development of this thesis and myself as a researcher. I would also like to thank for helpful critical reviews of the manuscripts and thesis proper. My appreciation is extended to and for supplying the sweet potato varieties, and to for insect identification. I wish to express my gratitude to my colleague and friend, for his advice and assistance along the way. and his wife, , made Virginia a much better place to live. I am indebted to who helped statistically, verbally, and physically in many of my research endeavors. Finally, I would like to express my appreciation to for some typing and proof reading, and for providing incentive during the last few months. iii TABLE OF CONTENTS Acknowledgements iii List of Figures vii List of Tables ix I. Introduction 1 II. Literature Review 3 The Genus Convolvulus 3 A. Convolvulus arvensis - Field Bindweed 4 B. Convolvulus sepium - Hedge Bindweed 5 Biology of Bindweed 8 Control of Bindweed 12 A. Legislative Control 13 B. Mechanical and Physical Control 13 C. Cultural Control: Cropping and Competition 14 D. Chemical Control 15 E. Current Control Methods 16 F. Biological Control 19 G. Taxonomy 20 a) Oidaematophorus monodactylus (L.) 20 b) Bedellia somnulentella (Zeller) 21 Ipomoea batatas (L.) Lam. - Sweet Potato 23 The Biological Control of Weeds 24 iv III. Bionomics of Oidaematophorus monodactylus on Hedge Bindweed in Southwestern Virginia: A. Introduction 26 B. Materials and Methods: a) Oviposition Studies of Adults 27 b) Egg and Larval Development 28 C. Results and Discussion: a) Adult Stage: Description and Oviposition Studies 29 b) Egg Stage 32 c) Larva!' Stage 32 d) Pupal Stage 37 e) Life-Cycle 37 IV. Feasibility of Using Oidaematophorus monodactylus as a Biological Control Agent of Hedge Bindweed: A. Introduction 41 B. Materials and Methods: a) Ovipositional Preference Test 42 b) Development on Different Varieties of Sweet Potato 43 c) Effectiveness of O. monodactylus in Suppressing Hedge Bindweed: (i) Greenhouse Cage Study 43 (ii) Field Cage Study 44 d) Colony Initiation, Mass Rearing, and Cost Analysis 45 C. Results and Discussion: a) Ovipositional Preference Test 47 b) Development on Different Varieties of Sweet Potato 47 v c) Effectiveness of Q. monodactylus in Suppressing Hedge Bindweed: (i) Greenhouse Cage Study 48 (ii) Field Cage Study 51 d) Colony Initiation, Mass Rearing, and Cost Analysis 57 V. Studies on the Development and Reproduction of Bedellia somnulentella on Hedge Bindweed and Sweet Potato: A. Introduction 66 B. Mat~rials and Methods: a) Adult Data: Effect of Sex Ratio on Fecundity and Longevity, and Oviposition Preference 68 b) Egg, Larval and Pupal Development 70 c) Development of B. somnulentella on 9 varieties of Sweet Potato 70 C. Results and Discussion: a) Adult Data: Effect of Sex Ratio on Fecundity and Longevity, and Oviposition Preference 71 b) Egg, Larval and Pupal Development 74 c) Development of B. somnulentella on 9 Varieties of Sweet Potato 78. Summary 80 Literature Cited 83 Vita 92 Abstract vi LIST OF FIGURES Fig. 1. - Adult female plume moth, Oidaematophorus monodactylus. 30 Fig. 2. - Rearing jar of O. monodactylus adults. 31 Fig. 3. - Various stages of O. monodactylus: A) eggs, B) 1st instar, and C) 2nd instar. 33 Fig. 4. - Results of the Greenhouse Cage Study: A) day of release of 1st instars, B) 20 days after release (5 larvae per leaf). 50 Fig. 5. - Cages used in the Field Cage Study: A) cages with their corresponding skirts set in position, B) one cage in its final position with dirt filled in. 52 Fig. 6. - Effect of varying densities of O. monodactylus larvae on leaf and shoot production and total length of a hedge bindweed plant. 54 Fig. 7. - Fourth instar of Q· monodactylus. 56 Fig. 8. Larval rearing apparatus: A) 120 ml container with bindweed, B) vials with water, C) vial rack. 59 Fig. 9. - Rate of O. monodactylus hatch after different periods at 4.40 C (r = -0.98). 60 Fig. 10. - Bell-shaped rearing jar of B. somnulentella adults. 69 Fig. 11. - Adult female leaf miner, Bedellia somnulentella. 72 vii Fig. 12. - Effect of sex ratio on the fecundity of B. somnulentella (r = -0.97). 73 Fig. 13. - Fourth instar of B. somnulentella: A) inside a mine in a sweet potato leaf, B) on the surface of a sweet potato leaf. 77 viii LIST OF TABLES Table 1. - Distinguishing characters of field and hedge bindweed. 6 Table 2. - Differences between the bindweeds used for quick field identification. 7 Table 3. - Descriptive data on the developmental stages of _Q. monodactylus. 34 Table 4. - Development and feeding of 0. monodactylus at different temperatures. 36 Table 5. - Larval development time, feeding capacity, and weight of Q. monodactylus at different temperatures. 38 Table 6. - Comparison of observed life cycles of 0. monodactylus in different areas. 39 Table 7. - Effect of varying densities of 0. monodactylus larvae released on caged hedge bindweed plants in the greenhouse and resulting adult emergence. 49 Table 8. - Effect of varying densities of _Q. monodactylus larvae released on caged hedge bindweed plants in the field and resulting adult emergence. 53 Table 9. - Rearing data for Q. monodactylus. 61 Table 10. - Proposed schedule for rearing 10,000 third instars of Q. monodactylus at 23.9 0 C, 15-h photoperiod, RH 60-90% in southwestern Virginia. 62 ix Table 11. ~ Cost estimate to initially rear 10,000 Q. monodactylus larvae on hedge bindweed. 63 Table 12. - Effect of temperature on the development of B. somnulentella. 75 x I. INTRODUCTION An important aspect of the biological control of a weed is to survey the insect fauna associated with the target weed throughout its growing season. This should: 1) provide information about the success of the weed, 2) reveal any insects, either indigenous or naturalized,. which appear to have an impact on its normal development and 3) prevent the introduction of potential control agents which are already present. Basic studies on the insects and factors affecting their ability to control the weed would help in the selection of potential biological control agents. It may be possible to introduce a closely related species which can avoid being restricted by limiting factors and thus be more effective in controlling the weed. The possibility also exists of aug- menting the population of a potentially effective species by increasing its numbers or improving its synchronization with the target host. Inundative releases for the control of an insect pest has its roots in classical biological control (Debach 1964; Stinner 1977). Although this has not been attempted in the biological control of weeds, the augmenta- tion of Bactra verutana Zeller for the control of nutsedge was advocated by Frick and Garcia (1975) and Frick (1977). A survey of the insect fauna associated with hedge and field bind- weed (Convolvulus sepium L. and f· arvensis L., respectively) in Virginia was initiated in 1972 (Parrella and Kok 1975). Most of the sampling and subsequent work involved only hedge bindweed because of its abundance in Montgomery and surrounding counties. Based on the preliminary surveys, two insects feeding on this weed were selected for further studies. -1- -2- These are the plume moth, Oidaematophorus monodactylus (L.) (Lepidoptera: Pterophoridae), and the "Morning Glory Leaf Miner", Bedellia somnulentella (Zeller) (Lepidoptera: Lyonetiidae). Previous workers (Mohyuddin 1969; Ghani et al. 1975) indicated that both these insects have potential as biological control agents of Convolvulus spp. where sweet potato (Ipomoea batatas (L.) Lam.) is not grown conunercially. However, some questions relating to the insects' effectiveness, reproductive capacity, and host preference would have to be resolved before a control program using these insects as control agents could be initiated. This study was undertaken to ascertain: 1) further developmental aspects of these insects on bindweed and sweet potato, 2) their effectiveness in controlling bindweed in the field, and 3) the feasibility of using them in a biological control program. II. LITERATURE REVIEW The Genus Convolvulus L. The genus Convolvulus L. of the tribe Convolvuleae (fam. Convolvulaceae) contains about 200 species (Bailey 1949), all of which are Eurasian in origin. This genus is derived from the Latin word convolvere, meaning to entwine. In temperate regions, the Convolvulaceae are mostly twining or trailing plants. Most of the species are weeds; a few are cultivated as ornamentals. Rickett (1966) recognized 3 species of Convolvulus occurring in the northeastern United States: C. arvensis L., f· sepium L., and f· spithamaeus L. The latter species is not recognized as an economically important weed by the Weed Science Society of America (Darrow et al. 1967) and is not considered further in this thesis. Fernald (1950) included two other genera in the genus Convolvulus: Volvulus Medic. and Calystegia R. Br. (Gray). In general Convolvulus spp. are perennial weeds with the following characteristics: style undi- vided and cleft at the apex; corolla funnelform to campanulate; stamens present; 2 stigmas linear-filiform to subulate or slenderly ovoid; capsule globose to sub-globose; 2 locular or 4 imperfectly locular or 1 locular by abortion. The plants may be shrubby, twining erect or prostrate. The most striking anatomical characteristic of the family Convolvulaceae is the occurrence of rows of secretory cells with milky, resinous contents (Wagner 1973).