Summary.1The occurrence of baeteriosis ofD. glomerata, with which is associated the non‐motile organismA. RathayiE. F. Smith, is recorded for Cambridgeshire definitely for the first time, but there seems little doubt that the disease has been present unrecognised for some time and is being constantly introduced on imported Danish seed.2The disease is similar to that originally observed near Vienna in 1897, but differs from the latest account from Germany where the damage caused was far more severe. The general symptoms were partial or complete destruction of the spikelets which were embedded in a bright yellow bacterial slime.3The associated organism was isolated and found to agree exactly in its cultural and growth characters with the descriptions of Rathay and Smith.4The naturally occurring bacterial slime proved pathogenic when inoculated into a healthy shoot ofDactylis, but no infection resulted when pure cultures on artificial media were use