Emerging vector borne diseases have significant ecological and economic impacts throughout the world. Because emergence of a disease is unpredictable, understanding of the pathogen manipulation of host and vector is critical to manage the disease. Successful bacterial pathogens modify host physiology, including defences, by secreting small proteins called effectors. Candidatus Liberibacter solanacearum (CLso) is an emerging, unculturable, slow growing, phloem-limited bacterium associated with multiple economically important diseases in Solanaceous crops. CLso is transmitted by the potato and tomato psyllid Bactericera cockerelli. Currently there is no genetic resistance to CLso in cultivated plant germplasm and increasing resistance to insecticides pose a high risk for disease epidemics. In this dissertation, I studied Lso effectors to gain insight into disease development. SEC secreted effectors were identified from four different CLso haplotypes. CLso effector subcellular localization, cell-to-cell movement and expression patterns were determined. Our results demonstrate that CLso differentially deploys suites effectors capable of targeting diverse eukaryotic subcellular compartments to modify its insect vector and tomato host. We also evaluated the ability of CLso effectors to suppress early markers of plant defense in response to perception of pathogen and vector features. Despite diverse subcellular localizations, the majority of tested effectors were unable to suppress host immune responses, indicating CLso relies on only a few effectors to suppress plant defense, unlike other well characterized plant pathogenic bacteria. Plants infected with bacterial vector-borne pathogens exhibit altered plant morphology and color. These alterations increase attractiveness of insect vectors and facilitate disease spread. To understand the role of CLso effectors in plant metabolism and architecture we deployed a PVX-mediated screening. We identified a suite of effectors that induce chlorosis and enhance viral symptoms in Nicotiana benthamiana. We also identify one effector able to induce systemic necrosis in tomato cv Micro-tom. Understanding the mechanisms that underlies CLso effectors induced necrosis will be an important step to generate resistant cultivars. Collectively, this study represents the first characterization of CLso effector repertoire and highlights key effectors that may shed light onto phloem disease biology.