Erwinia amylovora causes fire blight disease of apple, pear, quince, blackberry, raspberry and many wild and cultivated rosaceous ornamentals. The disease develops sporadically, but, occasionally, it is highly destructive, especially to young fruit trees that may be killed outright by infections that girdle the trunk or the rootstock. The pathogen is distributed widely in temperate regions in which rosaceous plants thrive. It was described initially as Micrococcus amylovorus, and then Bacillus amylovorus (Burrill), under the erroneous assumption that it destroys starch. It is Gram negative, rod shaped and motile with peritrichous flagella. It was renamed Erwinia amylovora (Burrill) Winslow et al. in the early 1900s and remains the type species of the genus. Closely related bacteria that elicit symptoms reminiscent of fire blight, particularly, but not exclusively, in pear, have been described as new species, e.g. E. pyrifoliae and E. piriflorinigrans.