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Fireblight, a highly destructive disease of several members of the rose family, is caused by the bacterium Erwinia amylovora. This bacterial organism is native to North America and is present throughout the continent where susceptible rose family hosts are grown. In Alberta, this disease can affect many highly desirable hardy ornamentals and fruit-producing species in the rose family including apple, crabapple, cotoneaster, hawthorn, pear, mountain ash, raspberry, saskatoon berry, plum and cherry. It is particularly destructive to species that are not native to Canada such as crabapple, apple and pear.