The innovations provides an antimicrobial and synergistic phytochemical composition, consisting of two active ingredients (FZ and YC). This innovation also consists of formulation processes and its applications to fungi, bacteria and/or virus-caused plant diseases such as citrus Huanglongbing, grape downy mildew, strawberry gray mold etc. This innovation combines two ingredients (FZ and YC) with different modes of action, dramatically improving plant inducible acquired resistance. Therefore, this composition dramatically enhances the control efficacy of plant diseases caused by fungi, bacteria or virus, expands the antimicrobial spectrum and promotes the plant growth.