REPORT OF THR SOCIETY 107 



The rhizome type of Iris is not an important host for fungus parasites, and 

 the growers lay very little stress on the damage they cause. The bacterial rhi- 

 zome rot, however, has been becoming more serious in recent years. 



As has been already stated, in the year 1901 and 1902 the disease was extre- 

 mely bad among the Iris plantations in Holland and caused extremely heavy 

 losses to the growers especially in the vicinity of Sassenhem. This is the only 

 report of the disease haVjing occurred in Europie. A thorough search through 

 the literature has giVen the writer very little information on the economic impor- 

 tance (jf the disease in this country. It is nevertheless present, because, in 

 various publications, such as E. F. Smith (9) and J. E. Howitt (5), it has been 

 mentioned that there is a bacterial disease which causes the rotting of the Iris 

 rhizomes. 



The writer's investigations have shown this disease to be of considerable 

 economic importance to growers, both in Quebec and Ontario. A few years ago, 

 Mr. T. G. Bunting, Professor of Horticulture at Macdonald College, obtained a 

 large number 6f different varieties of liris, to be used for decorative purposes 

 around the College campus. The original collection of two hundred and fifty 

 different varieties has been reduced to eighty by the ravages of this bacterial 

 disease during the past five years. La^ge numbers of infected plants have also 

 been found in the immediate vicinity of Montreal. Often they were complete- 

 ly destroyed by the disease, thus rendering them useless for decorative purposes 

 and a menace to the surrounding plants which are susceptible to the same patho- 

 gen. 



In the summer of 1921, the writer, on corresponding with Professor Howitt 

 of the Ontario Agricultural College at Guelph, was able to obtain the names of 

 two men, namely C. E. German, of London, Ontario, and C. R. C. Clarkson, of 

 Toronto, Ont., who had been seeking information from him regarding the rot in 

 question. Communication with these two men brought to Ijght the fact that in 

 their respective districts the soft rot of Iris was causing considerable loss to many 

 growers, owing to the destruction of valuable specimens. 



In the light of the above facts, there can be very little dobt that the bacte- 

 rial soft rot of Iris is a disease of considerable economic importance. It is true 

 that the districts from which it has been re ported are not extremely numerous 

 but that is no proof that the disease is not widespread. The reason why so 

 little stress has beeen laid on the disease is because those who grow Iris plants in 

 large numbers are not very numerous, and when small growers lose and occa- 

 sional specimen comparatively little attention is paid to the matter. 



