A new bacterial disease of date palm ‘sudden decline’ was found in the Al-Qassim region, Saudi Arabia. It is characterized by a sudden loss of vigor in the affected trees with the appearance of some blighted inner leaves. Symptoms develop rapidly and the whole tree assumes a straw color in about 2 weeks. The bud union is killed, and massive amounts of slime in a gel-like matrix could be detected in the heart of the affected tree. Biological and physiological tests of the isolated bacterium suggested that it belongs to the species Erwinia chrysanthemi. Artificial inoculation of various date palm cultivars using the technique of infusion under reduced pressure demonstrated that E. chrysanthemi was the causal agent and that cv. Succary was the most susceptible cultivar, whereas cvs. Roshody and Helwa were resistant to infection with E. chrysanthemi.