The present invention refers to the strain CECT8836 of Bacillus amyloliquefaciens and mutants thereof, and the use of said strain as a pesticide in controlling plant diseases caused by fungi and bacteria. Further aspects of the invention relate to methods for preparing suspensions and extracts of the strain CECT8836 of B. amyloliquefaciens, pesticidal compositions comprising said strain and an extract of CECT8836 of B. amyloliquefaciens with antimicrobial activity. Finally the invention relates to a method for the biological control of various plant diseases caused by fungi and bacteria both in vegetable plants and in fruit trees, comprising treating these plants with the strain CECT8836 of B. amyloliquefaciens, a composition including it or a cell-free extract derived from CECT8836 of B. amyloliquefaciens.