106 PROTECTION OF PLANTS — 1922-23 



Hewitt (5) gives a similar list o; soft rots caused by Bacillus Carotovorus but he 

 adds that it also causes a soft rot of the German Iris. It is possible that other 

 authors have mentioned this disease, but the writer has not been able to find 

 other citations. 



History and geographical distribution. 



The knowledge of the history and geographical distribution of this disease is 

 cotoiparatively vague. The first report of the Bacterial Rhizome Rot of Iris is 

 that of Van Hall, who found specimens of the disease at Sassenheim, in Holland, 

 in the year 1901. He investigated it and described it rather fully in his publica- 

 tion of 1903 (10). During the years directly following this discovery, the di- 

 sease was found in various parts of the United States by both E. F. smith and 

 L. R. Jones. Thej^, however, did not investigate the disease, since at the time 

 they were working on the soft rots of vegetables, principally the cabbage and the 

 carrot. The organism causing these rots was isolated by them and described as 

 Bacillus Carotovorus. The present writer has been unable to obtain any litera- 

 ture in which either of these workers made special studies of the soft rot of the 

 Iris, but Smith (9) states that the disease is caused by the same (or a similar) 

 organism as the one causing the soft rot of cabbage, namely. Bacillus Carotovorus 



The writer has found that the disease is present at, and in the vicinity of ,. 

 Macdonald College, the city of Montreal, and around London and Toronto 

 in Ontario. 



Investigations tend to show that the soft rot of the Iris rhizomes resemble^ 

 very closely the rot of the cabbage, turnip, and other vegetables, not only in the 

 effect on the host, but also in the nature of the causal organism. Since th& 

 bacterial soft rot of vegetables has been reported from practically all places where 

 the host plants are cultivated, and since the chmatic conditions which favour 

 the growth of these vegetables are also very similar to, and sometimes identical 

 with those in which the Iris thrives, it is not at all improbable that wherever 

 soft rot of vegetables is found the bacterial soft rot of the Iris will also occur. 



Eonomic importance. 



Members of the genus Iris are important commercial plants used for both 

 outside decorative purposes and also in the cut flower industry, but the first 

 mentioned purpose is the more important. There are two types of Iris, the one 

 with and the other without a rootstock or rhizome. The type having the rhi- 

 zome, although it is of less commercial value than the latter type, is by far the 

 more popular on account of the extreme ease with which it can be cultivated . 



