The program research objectives are to develop an effective and sustainable bacteriophage (phage)-based biocontrol system for Xanthomonas axonopodis pv. citri (Xac), the causal agent of citrus canker. Our approach has been to develop a bank of virulent (lytic) phages and/or antibacterial particles called �tailocins�, which are derived from phages. We have identified seven tailocins with activity against Xac and developed a large bank of virulent phages representative of the Caudovirales (tailed phages). The tailocins are protein assemblages that function like phage tails and kill the target bacterial cell by adsorbing and puncturing the cell envelope. In two independent experiments, a cocktail composed of tailocins XT-1 and XT-4 showed efficacy in reducing canker symptoms, when applied as a foliar spray, post application of Xac. Current efforts are directed towards isolating additional tailocin producing strains that are active against Xac. As reported previously, we are also focused on completing the characterization of Xac phages. We have determined that the burst size for CCP504, a virulent KMV-like phage, is ~70 PFU/cell and that the burst size for CCP513, a siphophage, is ~80 PFU/ cell. Abortive lysogeny tests are ongoing to reconfirm virulent status of cocktail phages. Further characterization of the two non-type IV pilus dependent phages, previously reported, determined that both phages had limited host ranges and would not be candidates for development of phage cocktails.