52 Bacterial Blight of Pear Blossoms in South Africa 



yet been ascertained whether this is identical with the blight at the 

 Cape or not. With the exception of a case of infection reported from 

 Wynberg, therefore, the disease is only known to occur up to the present 

 in Ihe 8tellenbosch District and at Elsenberg. It is particularly in- 

 teresting to find that there are three organisms showing a parasitism, 

 in many respects similar, in different parts of the world : it is therefore 

 my intention to describe the South African disease, and to compare it 

 with the blossom blight occurring in England and with that caused 

 by the fire blight bacillus in America. 



Through the courtesy of Professor Barker and Mr Grove who supplied 

 me with a culture of their organism I have been able to make a detailed 

 comparison of the South African and English bacteria. My knowledge of 

 the American blight is less complete, being gathered from the literature 

 to which I have access, and which is by no means exhaustive ; sufficient 

 information has been gathered by this means, however, to establish 

 the main points of difference between Bacillus amylovorus and the 

 other organisms causing blossom blight in pears. 



I. Fire Blight. 

 Bacillus amyloiionts (Burr) de Toni. 



The information summarised in the succeeding paragraphs has been 

 derived from the publications listed in the " Literature cited " (numbers 

 4—11). 



" Fire blight " was one of the first bacterial diseases of plants to be 

 recognised as such, and consequently has been studied in considerable 

 detail. It is very widely distributed in the United States and in Canada, 

 and has recently been recorded (8) from several places in Italy. It 

 causes very serious losses, amounting in California in the last fifteen 

 years to one-third of all the full-grown orchards, and to a money loss 

 estimated at $10,000,000 for the five years preceding the efforts for its 

 restriction begun in 1905 by the United States Department of Agri- 

 culture (8). 



In 1912 a variety of pear in Switzeiland was severely injured by a 

 bacterial invasion (7). It is thought that the disease may be similar 

 to the pear blight in America caused by Bacillus amijlovorus, but com- 

 plete identification of the organism has not yet been found possible. 



Although most common and most disastrous on the pear (Pyrus 

 communis) Bacillus amylovorus is also found as a parasite on the apple 

 {Pyrus malus), Quince {Cydonia vulgaris), a number of species of Prunus 



