Summary Brenneria salicis has been studied in willow wood only in relation to watermark disease. In this pathogenic condition, the bacterium occurs at high concentrations. Pathogenicity of B. salicis is still uncontrollable and the disease unpredictable because the plant–bacteria interaction is not understood. Thanks to molecular techniques B. salicis can be detected at low concentrations, which are found in most non‐pathogeni...

Summary Brenneria salicis resides in symptomless willow ( Salix spp.) and other tree species, but only willow trees develop watermark disease. To understand the conversion of B. salicis into a pathogen, its pathogenicity and differential growth in the various tree species are studied. Brenneria salicis was detected by plating and polymerase chain reaction‐based techniques. Cell wall degradation and quorum sensing (QS) were ass...