The Collaborative International Dictionary of English v.0.48:

Erwinia \Erwinia\ prop. n. [after Erwin F. Smith, an American
   pathologist. --RHUD]
   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.
   [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

erwinia
    n 1: rod-shaped motile bacteria that attack plants