The goal of the research is to control citrus HLB using small molecules which target essential proteins of Candidatus Liberibacter asiaticus (Las). In our previous study, structure-based virtual screening has been used successfully to identify five lead antimicrobial compounds against Las by targeting SecA. SecA is one essential component of the Sec machinery. Those compounds showed promising antimicrobial activity. However, further work is needed to apply the compounds. We will evaluate the important characteristics of our antimicrobial compounds including solvents and adjuvants, phytotoxicity, antimicrobial activities against multiple Rhizobia, antimicrobial activity against Las, application approaches, and control of HLB. Those information are critical to for the practical application of those antimicrobial compounds in controlling HLB. We also propose to further optimize the five lead compounds. In addition, we propose to develop antimicrobial compounds against lipid A of Las. The lipid A substructure of the lipopolysaccharides (LPS) of Sinorhizobium meliloti, which is closely related to Las, suppresses the plant defense response. Las contains the complete genetic pathway for synthesis of lipid A. We hypothesized that Las uses lipid A to suppress plant defense. Thus, targeting lipid A could activate plant defense response. Lipid A is also an ideal target and has been targeted for screening antimicrobial compounds for multiple pathogenic bacteria. We have identified multiple small molecular ‘or’ peptide inhibitors against LipidA using pharmacophore based methods and are finalizing the list of the compounds for the activity studies. Six lipid A inhibitors have been ordered and are being tested against Las and its relatives. Our preliminary data showed that the lipid A inhibitors have excellent antimicrobial activities against L. crescens and other Las relatives. One manuscript on lipid A inhibitor is being prepared. For SecA inhibitors, we are optimizing the compounds in collaboration with IBM. Two compounds with slightly higher binding affinity than C16 were identified. We also identified multiple SecA inhibitors. The antimicrobial activities of the newly identified SecA inhibitors have been tested. Currently, we are evaluating the best range of composition ratio among each component (%weight) of AIs, solvents and surfactants. The following characteristics are being evaluated: 1) emulsion stability and ease of emulsion; 2) stability of diluted concentrate; 3) freeze-thaw stability; and 4) phytotoxicity to citrus species. We have successfully identified one formulation suitable for all SecA inhibitors without phytotoxicity. Using the formulation, we have tested all five compounds against eight different bacterial species including Liberibacter crescens, E.coli, Agrobacterium, and Sinorhizobium. The formulation has significantly improved the antimicrobial effects of SecA inhibitors, comparable to streptomycin. The data has been summarized in one manuscript being submitted. Overall, this project generated multiple antimicrobials with potential against Las, which were summarized in two manusscripts. One patent has been filed for SecA inhibitors.