THE DISEASES OF ROSES. 



By Louis M. Massey, Assistant Professor of Plant 

 Pathology, Cornell University, Ithaca, N. Y. 



Read before the Society, February 23, 1918. 



The John Lewis Russell Lecture. 



The rose was probably the first flower cultivated for ornament 

 or for perfume. Being native to the north temperate zone it 

 occurs within these limits entirely around the world and is grown 

 in all temperate climates. Millions of roses for the market are 

 produced in large glasshouses in order that blossoms may be had 

 throughout the year. In the value of the crop the rose easily 

 leads all other flowers grown under glass, while its importance as a 

 garden plant is too well known to need comment. 



That the rose is subject to numerous diseases is a matter of 

 common observation. Doubtlessly all growers and fanciers are 

 familiar with the two most serious diseases, black-spot and mildew. 

 These may be said to be ubiquitous, while the attention of rosarians 

 is focused on various other diseases of more or less general occur- 

 rence as they assume an epiphytotic nature. Some of the diseases 

 are fairly common in the wild but have come into prominence 

 only as the rose has become of commercial importance. Other 

 diseases have probably had a later development and are becoming 

 of more and more importance under present intensive methods of 

 propagation. In catering to the demands of the trade and of the 

 fanciers, many new types have been developed by breeding and it 

 is probable that the natural resistance of wild forms brought about 

 through the process of the survival of the fittest has been sacrificed. 



The scarcity of definite information is one of the noticeable 

 phases of the subject "diseases of roses." This situation finds 

 explanation in the fact that diseases of ornamental plants in general 



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