Erwinia amylovora is a gram-negative phytopathogenic bacterium causing fire blight on a range of rosaceous plants including economically important ones such as apple and pear. Methods to substitute for the application of streptomycin in fire blight control include the application of antagonistic bacteria. Highly specific pathogen suppression can be achieved by interfere with “quorum sensing” regulated expression of virulence factors. In case of E. amylovora the production of an autoinducer 2 signal has been demonstrated. The current project investigates the impact of quorum sensing on the pathogen and searches for suitable targets to interfere. Antagonistic bacteria that are known to suppress E. amylovora are examined for their ability to meddle with the signaling pathways of the pathogen.