Compositions contain anti-microbial agents that can kill, inhibit, and/or prevent the growth of the microbes. The composition contains carrier and/or retainer forms a protective barrier on the surface of the plants when the composition is applied onto the plants. The carrier forms one or more layers of bio-barrier, which serves as a protective layer preventing microbes and/or other harmful microorganisms or virus from contacting and infecting the plants. The retainer serves as a chemical glue (e.g., a water soluble glue) for increasing the contact time and contact numbers between the anti-microbial agents and the harmful microbes. The compositions are all made from ingredients that are from food-grade, organic, or GRAS (Generally Recognized as Safe) materials under 21 C.F.R. 174-178 (C.F.R.: U.S. Code of Federal Regulations).
