THE DISTRIBUTION OF THE BLACK PECAN APHID MELANOCALLIS CARYAEFOLIAE (HOMOPTERA: APHIDIDAE) BETWEEN THE UPPER AND LOWER SURFACES OF PECAN FOLIAGE by CHRISTIAN M. PAULSEN, JR. (Under the Direction of John Ruberson) ABSTRACT An orchard survey determined that nymphs of M. caryaefoliae regularly feed on both surfaces of pecan foliage, while other pecan aphids feed predominately on the lower leaf surface. Aphid populations on laboratory pecan seedlings were similarly distributed. Comparison of M. caryaefoliae nymphs reared on each leaf surface found the upper surface offers no fitness advantage. Observations of aphid density found evidence that crowding by heterospecific aphids contributes to M. caryaefoliae movement to the upper surface, while conspecific crowding has no effect. Field observations and experiments on laboratory seedlings found that some aphidophagous lady beetle and lacewing larvae predominately search the lower leaf surface for prey. M. caryaefoliae may settle on the upper leaf surface because it is a habitat with reduced probability of enemy encounters. INDEX WORDS: Melanocallis caryaefoliae, Aphididae, Homoptera, enemy-free space, foliage-feeding, crowding, Monellia caryella, Monelliopsis pecanis, Coccinellidae, Chrysopidae. THE DISTRIBUTION OF THE BLACK PECAN APHID MELANOCALLIS CARYAEFOLIAE (HOMOPTERA: APHIDIDAE) BETWEEN THE UPPER AND LOWER SURFACES OF PECAN FOLIAGE by CHRISTIAN M. PAULSEN, JR. Bachelor‘s of Science, Purdue University, 2006 A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree MASTER OF ENTOMOLOGY ATHENS, GEORGIA 2011 © 2011 Christian M. Paulsen, Jr. All Rights Reserved THE DISTRIBUTION OF THE BLACK PECAN APHID MELANOCALLIS CARYAEFOLIAE (HOMOPTERA: APHIDIDAE) BETWEEN THE UPPER AND LOWER SURFACES OF PECAN FOLIAGE by CHRISTIAN M. PAULSEN, JR. Major Professor: John Ruberson Committee: Ted Cottrell Dan Horton Kerry Oliver Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia May 2011 ACKNOWLEDGEMENTS The author thanks A. Amis, S. Calhoun, S. Starks, and V. Thomas (USDA-ARS, SEFTRL, Byron, GA) for technical assistance as well as A. Nyczepir (USDA-ARS, SEFTRL, Byron, GA) for the use of lab space. This article reports the results of research only. Mention of any brands or proprietary products does not constitute an endorsement by the USDA or the University of Georgia. iv TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ........................................................................................................... iv LIST OF TABLES ........................................................................................................................ vii LIST OF FIGURES ..................................................................................................................... viii 1 INTRODUCTION .........................................................................................................1 2 LITERATURE REVIEW ..............................................................................................2 Pecan ....................................................................................................................... 2 Aphids. .................................................................................................................... 4 Natural enemies. ................................................................................................... 10 References ............................................................................................................. 12 3 DISTRIBUTION OF THE BLACK PECAN APHID (HOMOPTERA: APHIDIDAE) ON UPPER AND LOWER LEAF SURFACES .........................................................19 Abstract ................................................................................................................. 19 Introduction ........................................................................................................... 20 Materials and Methods .......................................................................................... 23 Results ................................................................................................................... 27 Discussion ............................................................................................................. 31 References ............................................................................................................. 37 Tables .................................................................................................................... 43 Figures................................................................................................................... 45 v 4 TOP OR BOTTOM: EFFECTS OF LEAF SURFACE AND PREDATION ON BLACK PECAN APHID MELANOCALLIS CARYAEFOLIAE DISTRIBUTION ON PECAN FOLIAGE ......................................................................................................65 Abstract ................................................................................................................. 65 Introduction ........................................................................................................... 66 Materials and Methods .......................................................................................... 69 Results ................................................................................................................... 76 Discussion ............................................................................................................. 81 References ............................................................................................................. 86 Tables .................................................................................................................... 91 Figures................................................................................................................... 92 5 DISCUSSION ............................................................................................................102 References ........................................................................................................... 111 vi LIST OF TABLES Page Table 1.1. F-statistics and numerator degrees of freedom from ANOVA for the pecan aphids observed in the orchard from June through August 2009. ............................................................ 43 Table 1.2. F-statistics and numerator degrees of freedom from ANOVA for the aphid natural enemies observed in the orchard from June through August 2009. .............................................. 44 Table 2.1. F-statistics and degrees of freedom from ANOVA from predator behavior observations. ................................................................................................................................. 91 vii LIST OF FIGURES Page Figure 1.1. Aphid abundance from the field survey, pooled across sampling dates and trees. .... 46 Figure 1.2. Comparison of the effects of leaf surface and shade on M. caryaefoliae abundance. 48 Figure 1.3. Comparison of M. caryaefoliae nymph abundance between sun and shade foliage over time. ...................................................................................................................................... 50 Figure 1.4. Comparison of M. caryaefoliae nymph and adult abundance between leaf surfaces over time. ...................................................................................................................................... 52 Figure 1.5. Comparison of M. pecanis and M. caryella nymph and adult abundance between leaf surfaces over time. ........................................................................................................................ 54 Figure 1.6. Natural enemy abundance from the field survey, pooled across sampling dates and trees. .............................................................................................................................................. 56 Figure 1.7. Comparison of lady beetle larva abundance between sun and shade foliage over time. ....................................................................................................................................................... 58 Figure 1.8. Mean pecan aphid numbers from lab experiments. .................................................... 60 Figure 1.9. M. caryaefoliae distribution between leaf surfaces vs. density from solo lab experiments. .................................................................................................................................. 62 Figure 1.10. M. caryaefoliae distribution between leaf surfaces vs. density from mixed lab experiments. .................................................................................................................................. 64 Figure 2.1. Effects of leaf surface and orientation on M. caryaefoliae survival and occurrence of chlorosis. ....................................................................................................................................... 93 viii Figure 2.2. Effects of predator foraging on M. caryaefoliae and M. pecanis populations on laboratory pecan seedlings. ........................................................................................................... 95 Figure 2.3. Effects of predator foraging on pecan aphid populations on orchard pecan leaves. .. 97 Figure 2.4. Comparison of time spent by chrysopid or coccinellid larvae searching, resting,