Phages are part of the plant microbiota and promising biocontrol agents against bacterial pathogens, but numerous challenges and questions remain: What is the impact of phages on the diversity and pathogenicity of microbial communities in agriculture? Can we identify the optimal phage cocktails to be applied as biocontrol measures? Can we predict if phages will protect for a long time or will resistance inevitably arise? We currently work on phage interactions with two bacteria responsible for major plant diseases: Pseudomonas syringae and Erwinia amylovora. By bringing evolutionary biology, community ecology and molecular microbiology together, we aspire to unveil the role of phages for plant bacterial pathogens and to advance their development as biocontrol agents in agriculture.