Fire blight has been known as a destructive disease of apple and pear for over 200 years. The disease is caused by the bacterium Erwinia amylovora (Burrill) Winslow et al. It has been reported from 40 countries around the world and caused serious losses to pome fruits and ornamentals plants, especially Rosaceae family. In Egypt, during early of 1980, the disease became very severe, and about 80% of all pear acreage was affected and 50% of all trees had been eradicated, presumably due to an increase in rain during the blooming period.