The present invention describes applications and methods (1) to use bacteriophage Cf and its variants to prevent and treat the citrus canker pathogen, Xanthomonas citri subsp. citri； (2) to engineer recombinant Cf phages that the infectivity is controllable without being harmful to the rest of environment； (3) to engineer and produce recombinant Cf phages with longer storage shelf life； (4) to use Cf phage as a vector for the introduction and insertion of foreign genetic material into Xanthomonas citri subsp. citri. genome； (5) to use and engineer Xp12 and Xf bacteriophages to inhibit Xanthomonas oryzae pv. oryzae, the causal agent of the rice blight disease.
