STUDIES ON THE FIRE-BLIGHT ORGANISM, 

 BACILLUS AMYLOVORUS 1 



A. L. PlERSTORFF 



Investigators giving attention to the fire-blight disease of pear and 

 apple during the past several years have again placed in question 

 certain of the concepts which were generally regarded as established. 

 Besides presenting many important facts, these workers have added 

 to the long series of interesting questions which are urgently in need 

 of further study. . The writer began a study of certain phases of the fire- 

 blight problem in 1923, and continued at intervals until September, 

 1926. No attempt is here made to review the voluminous literature 

 relating to fire blight, except as it bears directly on the phases treated 

 in this paper. 



PLANTS AFFECTED 



Many workers have contributed to our knowledge of the species of 

 plants that may be infected by Bacillus amylovorus (Erwinia amylo- 

 vora). For the literature on fire blight preceding the classical work 

 of Burrill (1878, 1881a, 1881b), who discovered the causal organism 

 and proved apple, pear, and quince to be suscepts, the reader is referred 

 to the excellent reviews given by Arthur (1887c), Stewart (1913), 

 and Snow (1922). Burrill (1881b) included lombardy poplar, aspen, 

 maple, elm, linden, ash, lilac (leaves), butternut, and some herbaceous 

 plants (peony), in the list of suscepts. All of the above-mentioned 

 plants have since been eliminated as suscepts. Arthur (1885b:1183) 

 reports that "unsuccessful inoculation was made upon the mountain 

 ash (Pyrus aucuparia) , but as the tissues were already solid when done, 

 and as branches suffering with the disease have since been found, there 

 is no doubt that it can be communicated if the inoculation be properly 

 performed." 2 Waite (1896) includes mountain ash among the species 

 which should be inspected for blight in eradication work. Edwards 

 (1907), in speaking of fire blight, states that the cut-leaved mountain 



1 Also presented to the Faculty of the Graduate School of Cornell University, June, 1929, 

 as a major thesis in partial fulfillment of the requirements for the degree of doctor of 

 philosophy. 



Author's acknowledgments. The investigations discussed in this paper were under- 

 taken at the suggestion of Dr. H. E. Thomas. To him and to other members of the staff of 

 the Department of Plant Pathology at Cornell University the writer is greatly indebted 

 for helpful suggestions and criticisms, and he acknowledges his sincere appreciation. 



2 Sorbus aucuparia L. For botanical and horticultural names, the Manual of Cultivated 

 Plants, by L. II. l'.ailey, la used as authority. 



