Plants react to pathogen attack through a variety of active and passive defense mechanisms primarily related to the metabolism of phenolic compounds and oxidative metabolism. Thus the activation of defensive reactions is associated with the increased expression of a great number of genes that encode enzymes involved in the biosynthetic pathway of phenolic compounds. Similarly, the activation of oxidative metabolism precedes the expression of defense genes during plant-pathogen interactions, so both metabolic processes must exert a major function in directing the mechanisms to resist disease. Similarly, it has been suggested that certain fungicides used to mitigate or prevent pathogen attack may be involved in activating certain defensive responses of plants. However, the fact that such substances may influence the key steps of the phenolic and oxidative processes has scarcely been studied. Our work confirms the results proposed by other authors, who suggest that certain wide-spectrum fungicides, in addition to their antibiotic action against pathogens, may be involved in the activation of some defensive responses of plants.