The present invention relates to the use of the compound of the formula (I) and the composition thereof as control agent for plant diseases caused by fungi, oomycetes and bacteria. Plant pathogens produce self-aggregating proteins, like beta-amyloid proteins, that can be important parts of extracellular structures, for example cell walls, adhesion structures to biological surfaces and other pathogenicity related infection structures. This invention discloses that the compound of the formula (I) interferes with the aggregation of such proteins and thus reduce plant pathogen growth significantly.