USE OF CURRY LEAF (Murraya koenigii) AND VOLKAMER LEMON (Citrus volkameriana) AS POTENTIAL TRAP CROPS FOR THE ASIAN CITRUS PSYLLID (Diaphorina citri) IN A COMMERCIAL CITRUS GROVE A Thesis Presented to the Faculty of California State Polytechnic University, Pomona In Partial Fulfillment Of the Requirements for the Degree Master of Science In Agriculture Science By Amanda S. Marsh 2016 SIGNATURE PAGE THESIS: USE OF CURRY LEAF Murraya KOENIGII AND C. VOLKAMARIAN AS POTENTIAL TRAP CROPS FOR THE ASIAN CITRUS PSYLLID Diaphorina CITRI IN COMMERCIAL CITRUS GROVES AUTHOR: Amanda S. Marsh DATE SUBMITTED: Fall 2016 College of Agriculture Valerie Mellano, Ph.D. Committee Chair Department of Plant Sciences Eileen Cullen, Ph.D. Department of Plant Sciences Robert Green, Ph.D. Department of Plant Sciences ii ACKNOWLEDGEMENTS Psalms 111:2 The works of the Lord are great, studied by all who have pleasure in them. I want to thank God for giving me the idea for this project. It was a joy to study His creations! It has been my heart to serve the agricultural community through entomology. I was thankful that God gave me the opportunity to do so by further studying how plants and insects work together. I’d also like to thank my loving husband, Nathan, for encouraging me every step of the way. You’re my rock and my best friend. Thank you to Dr. Valerie Mellano and Dr. Eileen Cullen for providing constructive feedback and mentoring me during the process. Dr. Robert Green, thank you for your patience and thorough attention to detail. I’d also like to acknowledge the support of Dr. Anna Soper and Dr. Kimberley Miller. Each of you gave me support and tools I needed to be successful in this journey. Thank you. iii ABSTRACT Since the introduction of the citrus greening disease Candidatus Liberibacter asiaticus Huanglongbing (HLB), from Asian in 2005, Florida citrus production has been in steady decline. Curative treatments for HLB-infected trees are unavailable, and management strategies for the insect vector Diaphornia citri (Asian citrus psyllid (ACP)), have been unsuccessful in Florida. With initia l HLB detection in Los Angeles California in 2012, and recent detections near the first detection site, and establishme nt of ACP in San Diego, Orange, Imperial, and Los Angeles counties and in the San Joaquin valley due to greater than 50 ACP detections (University of California, Division of Agriculture and Natural Resources, 2016 c), there is growing concern for movement of the disease throughout the state. Novel ACP and HLB management strategies are needed. Trap cropping is an ecological approach to insect-pest management that utilizes preferred alternative insect host plants to lure the target insect pest away from the harvested agricultural crop. This methodology has not yet been attempted in citrus production with little understanding of trap crop potential for ACP in commercial citrus groves. This experiment applied current knowledge of ACP host plant preferences to evaluate Murraya koenigi, (curry leaf) and Citrus volkamariana as potential trap crops in and established commercial citrus orchard in Pomona, California. iv TABLE OF CONTENTS SIGNATURE PAGE .......................................................................................................... ii ACKNOWLEDGEMENTS ................................................................................................ iii ABSTRACT........................................................................................................................ iv LIST OF TABLES ............................................................................................................. vii LIST OF FIGURES .......................................................................................................... viii CHAPTER 1 ...................................................................................................................... 1 INTRODUCTION .......................................................................................................... 1 Objectives ....................................................................................................................1 CHAPTER 2 ...................................................................................................................... 2 LITERATURE REVIEW ............................................................................................... 3 2.1 Background ............................................................................................................3 2.2 HLB: History and Biology.....................................................................................3 2.3 ACP primary vector of HLB disease .....................................................................3 2.4 Economic impact of ACP and HLB ......................................................................7 2.5 HLB management needed....................................................................................10 2.6 Integrated pest management for ACP utilizing trap cropping .............................13 2.7 M. koenigii and C.volkameriana as potential trap crops for Asian citrus psyllid16 CHAPTER 3 .................................................................................................................... 18 MATERIALS AND METHODS.................................................................................. 18 3.1 Trap crop placement and sampling for ACP adults .............................................18 3.2 Monitoring flush and population densities ..........................................................19 3.3 Monitoring ACP movement ................................................................................20 v 3.4 Statistical analysis................................................................................................20 CHAPTER 4 .................................................................................................................... 22 RESULTS AND DISCUSSION ................................................................................... 22 4.1 Effects of trap crops on Diaphorina citri densities .............................................22 4.2 Adult ACP populations based on sweep sampling ..............................................23 4.3 Effects of trap crops on Diaphorina citri movement...........................................24 4.4 Effects of flush patterns on Diaphorina citri densities........................................24 4.5 Effect of trap crops on ant populations ..............................................................224 4.6 Correlations between dependent variables ........................................................224 CHAPTER 5 .................................................................................................................... 38 CONCLUSION ............................................................................................................. 38 5.1 Curry leaf and Volk as potential trap crops for ACP...........................................38 5.2 Implications of trap cropping for ACP and HLB management ...........................39 REFERENCES ................................................................................................................. 42 Definition of Terms .......................................................................................................... 48 vi LIS OF TABLES Table 4.1. The effecto fo volk and curry leaf on the average of eggs and the percent branches with flush ........................................................................................................... 25 Table 4.2.The effect of volk and curry leaf on the average of nymphs and adults per branch................................................................................................................................ 30 Table 4.3.The effect of volk and curry leaf on the percent flush growth and average adults per sweep........................................................................................................................... 33 vii LIST OF FIGURES Figure 4.1. Percent total branches with flush growth……………………………………6 Figure 4.2. Overall percent total branches with flush new growth……………………….7 Figure 4.3. Average ACP eggs per randomly selected branch……………………………8 Figure 4.4 Overall average ACP eggs per randomly selected branch …………………..29 Figure 4.5 Average number of adult ACP per randomly selected branch ………………30 Figure 4.6 Overall average number of adult ACP per randomly selected branch ………31 Figure 4.7 Average ACP adults per sweep net sample…………………………………..32 Figure 4.8 Overall average adult ACP per sweep net sample …………………………..35 Figure 4.9 Overall yellow panel trap placement effect on adult ACP …………………..37 viii CHAPTER 1 INTRODUCTION Since the introduction of the citrus greening disease Candidatus Liberibacter asiaticus Huanglongbing (HLB), from Asian in 2005, Florida citrus production has been in steady decline. In 2015, orange production will be the lowest in over 50 years as direct result of the disease. Curative treatments for HLB-infected trees are unavailable, and management strategies for the insect vector Diaphornia citri (Asian citrus psyllid (ACP)), have been unsuccessful in Florida. With recent HLB detection in Los Angeles California in 2016 (University of California Agriculture and Natural Resources Statewide Integrated Pest Management Program 2016d) and establishment of ACP in Los Angeles, Orange San Diego, and Imperial counties and San Joaquin valley (University of California, Division