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.
