There is disclosed the treatment of plant diseases by means of a composition comprising from 10 wt% to 55 wt%, with respect to the overall weight of the composition, of (elementary) sulphur； from 10 wt% to 35 wt%, with respect to the overall weight of the composition, of potassium bicarbonate； and from 10 wt% to 75 wt% with respect to the overall weight of the composition, of a mixture of amino acids and/or peptides； from the set of experimental tests performed, it is apparent that the various components of the composition have a significant and surprising synergical action.
