1. Continuuing to improve the defined medium (Cruz-Munoz et al. 2018) for the culture of Liberibacter crescens, the cloest cultured relative of the citrus greening pathogen. An analysis of the amino acid requirements of L. crescens shows that only a few are required for growth. Deletion of the other amino acids from the medium results in growth but it is reduced. During the growth of L. crescens, we found that the pH of the medium increases by over 1 pH unit. Buffering this pH change reduces growth. The cause of the pH increase is under investigation. Nabil Killiny has published that the pH of citrus phloem increased from 5.7 to 6.2 after infection. As a result, we believe that studying this phenomenon in L. crescens may give us translatable results to understanding the cause of disease symptoms. 2. Monitoring of citrus groves for non-target antibiotic resistance prior to and after application of streptomycin and oxytetracycline. We have a method for the rapid detection of streptomycin in the field. We now need to test it in the field. 3. Developing second-generation antimicrobial treatments for citrus greening disease. A new antimicrobial Presto-Blue assay was developed for L. crescens on M15 defined medium. It is being tested on compounds we believe may be important for HLB control. If we have success with these, we will inform CRDF. At the moment, one compound looks to be promising. We are moving forward with a test to determine the spontaneous resistance rate in L. crescens for this compound. 4. Phosphate utilization as a strategy for HLB-disease management A greenhouse experiment is still in progress to determine whether foliar phosphate fertilization can recude citrate levels in phloem. Citrate is a preferred nutrient for Liberibacter. Phosphate fertilization is expected to reduce those levels in phloem sharply, thereby starving the pathogen. The phosphate foliar treatments are provided three times per week in the citrus macrophylla seedlings. When the plants flush, we will move them to a psyllid room in Lake Alfred. Cruz-Munoz, M., Petrone, J. R., Cohn, A. R., Munoz-Beristain, A., Killiny, N., Drew, J. C., & Triplett, E. W. (2018). Development of chemically defined media reveals citrate as preferred carbon source for Liberibacter growth. Frontiers in Microbiology, 9, 668. Killiny, N. (2017). Metabolite signature of the phloem sap of fourteen citrus varieties with different degrees of tolerance to Candidatus Liberibacter asiaticus. Physiol. Mol. Plant Pathol. 97, 20-29. doi: 10.1016/j.pmpp.2016.11.004