2. Pathogenicity 
Tab A - Page 26 
P. s. syrlnoae Is a common plant epiphyte. It has never been shown to be 
a pathogen for humans or animals and dees not grow at mammalian body 
temperature or at any temperature above 33-34° C. Neither P. s_. svrlnqae nor 
Erwlnla herbicola Is a pathogen of potato (See Index of Plant Diseases in the 
U.S., Crops Res Civ, ARS, U.S.D.A., Aug. 1960; Compendium of Potato Diseases, 
W.J. hooker ed., Amer. Phytopathol. Society, 1981; Diseases of Potato, G.J. 
Brencheley and H.J. Wilcox, Ministry and Agriculture, Fisheries and Food, 
London , U.K. , 1979) . 
Certain strains or isolates of P_. s_. syrinqae have been reported to be 
pathogenic cn many woody and herbaceous plants including bean, lima bean, 
wheat, barley, sorgum, corn, pear, apple, plum, peach, cherry, citrus, and 
others. However, disease caused by this pathogen on these hosts is rare in 
California and probably occurred only after predisposition by frost injury. 
The pathogenicity of many isolates of pathogenic strains, obtained either 
from disease lesions on herbaceous hosts or from epiphytic inocula present on 
such hosts, is restricted to a few hosts which are closely related. This Is 
true, for example, for isolates from bean and stone fruits. Other studies, 
however, indicate less well defined host specialization (broader or overlapping 
host range for Individual Isolates), and P_. s_. syrinqae has been considered by 
some to be' a less specialized pathogen than otner £. syrinqae pathovars. 
However, there are several reasons to doubt many of the claims In the literature 
regarding its host range. For example, tests on host plants, in addition to or 
including the host of origin, were often conducted under conditions that were 
artificial in important respects: 
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