Fire blight is a serious disease of plants in the subfamily Maloideae, especially apple, pear, quince and loquat. Epidemics, although sporadic, are often devastating depending on the occurrence of favourable climatic conditions, the amount of initial inoculum and virulence of the pathogen, and the susceptibility of the host species. Therefore, in any given site where fire blight is present, the disease can either be devastating or of secondary importance, according to the year and the varieties grown.

 In addition, fire blight is a quarantine disease in most countries and, therefore, a single introduction, even of very limited importance in the field, may have a considerable economic impact in a newly infected country, due to the possible limitations in the international trade of plants.