a genus of rod-shaped motile bacteria, classed among the Enterobacteriaceae, that may attack plants. Species of Erwinia may also be cultured on artificial growth media.

Erwinia is a genus of Enterobacteriaceae bacteria containing mostly plant pathogenic species which was named for the first phytobacteriologist, Erwin Smith. It is a gram negative bacterium related to E.coli, Shigella, Salmonella and Yersinia. A well-known member of this genus is the species E. amylovora, which causes fireblight on apple, pear, and other Rosaceous crops.