It describes the disease cycle and offers advice for treatment and protection. It was first reported in the late 18th century in the Hudson River Valley in New York. The disease is indigenous to North America, and probably occurred on native American plants such as crabapple, hawthorn and mountain ash and then spread to susceptible cultivated apples, pears and woody ornamentals planted by the early American pioneers. As the settlers moved west, so did fire blight. By the early 1900s it became established as a serious threat wherever apples and pears were grown in North America.
Fire blight has a wide host range.
The pome fruits and many species in the rose family are susceptible. I is a partial list of susceptible hosts. Many selections of the callery pear used as ornamentals show resistance, as do a number of cultivars of apple and crabapple. In addition to these seven important hosts, there are plants in 33 additional genera in the family Rosaceae that are susceptible to fire blight. Some of these appear in Table I .