More details on Erwinia pyrifoliae
As already reported in EPPO RS 98/204, a new Erwinia species, named Erwinia pyrifoliae (EPPO Alert List) was isolated from necrotic Asian pear trees in the Republic of Korea. In 1995, unusual symptoms were observed on Asian pears (Pyrus pyrifolia cv. Shingo). Symptoms were characterized by black to brown stripes in the leaf midribs, dark brown leaf spots, necrotic petioles. Necrotic symptoms sometimes extended to large parts of the trees and affected entire branches, blossoms and fruitlets. It has been observed that large numbers of trees in an orchard could show symptoms. But so far, the extent and severity of this disease in Korean orchards is unknown. Bacteria were constantly isolated from necrotic branches. Microbiological, molecular and pathological tests showed that the isolated pathogen belongs to the genus Erwinia. It is closely related to E. amylovora but distinct from it. Most isolates allowed the verification of Koch's postulate on P. pyrifolia seedlings and on slices of immature pear fruits (P. communis). Therefore the name E. pyrifoliae was proposed. The host range of E. pyrifoliae remains to be studied. It is not known whether it is only restricted to Pyrus, or if it could infect Malus and other Maloidae or Rosaceae. The authors also noted that in recent unpublished molecular studies, isolates of a bacterium found in Japan and previously thought to be E. amylovora (although this was denied) were found to be related to E. pyrifoliae but distinct from E. amylovora.
Rhim, S.L.; Völksch, B.; Gardan, L.; Paulin, J.P.; Langlotz, C.; Kim, W.S.; Geider, K. (1999) Erwinia pyrifoliae, an Erwinia species different from Erwinia amylovora, causes a necrotic disease of Asian pear trees.
Plant Pathology, 48(4), 514-520.