WHIT?:-PIXE BLISTER EUST. 11 



nartium rihicola attacked Kibts aureum and R. odoratum after they 

 reached Europe. Their susceptibiUty also indicates that they are 

 not original hosts of the fungus. 



Summing up the evidence available, it appears (1) that Cronartium 

 ribicola is Asiatic in origin; (2) that it spread in the early 1800's 

 into western Russia, whence it eventually spread well over Europe 

 (41) ; (3) that it was brought to North America in young trees of 

 Pinus strohus; and (4) that comparative studies (50) show that 

 Cronartium occidentale is distinct. 



HOSTS OF CRONARTIUM RIBICOLA. 



Pines Infected and Likely to Become Infected. 



Cronartium rihicola has attacked 11 of the white pines in the 

 countries, Provinces, and States indicated in the following list : 



Pinus aristata Engelmann in England (20a). 



ayacahuite Ehrenb. in Scotland and England.^ 



cembra L. in Russia (58, 93), Switzerland (39, 40, 123, Germany (72, 77, 174, 177), 

 U. S. A. (Mass., Minn.)." 



excelsa Wall, in Denmark (120), Germany (99), U. S. A. (Mass.). 



fiexilis James in Germany (173), Sweden, ^ U. S. A. (Mass., Minn., Iowa). 



koraiensis Sieb. and Zucc. in Sweden.^ 



lavibcrtiana Douglas in Belgium (101), Germany (62, 173). 



monticola Douglas in Belgium (101), England (79), Germany (70). 



parvijlora Sieb. and Zucc. in U. S. A. (Mass.). 



peuce Gris. in Germany (173). 



strobus L. in Austria-Hungary (178), Belgium (70), Denmark (81, 115, 117, 119, 

 120), Finland (54, 83), Switzerland (40), France (70), Germany (70), X}reat 

 Britain (111), Holland (70), Ireland (42), Norway (70), Russia (27, 58, 120), 

 Siberia (161), Sweden (131 s), Canada— Ontario (23, 56) and Quebec (107, 

 121), U. S. A. (Conn., Ind., Iowa, Maine, Mass., Mich., Minn., N. H., N. J., 

 N. Y., Ohio, Penn., R. I., S. Dak., Yt., Va., Wis.). The fungus has occur- 

 red in a number of these States only on diseased pines shipped from outside 

 points. 



In every case the disease attacked these pines naturally in out- 

 break areas of Europe and North America and is not known to attack 

 any of the pitch pines, although some of them have been present in 

 infected areas. Whenever the other white pmes are continuously 

 exposed to the fungus they will be likely to develop the disease. The 

 blister rust was first found on the different species of pines as follows: 



Pinus strobus. Russia in 1854. Pinus ayacahuite. Great Britain in 1908. 

 lambertiana. Germany in 1887. fieodlis. Gennany in 1914. 



cembra. Russia in 1890. peuce. Germany in 1914. 



monticola. England in 1898. paniflora. United States in 1916. 



excelsa. Denmark in 1902. koraiensis. Sweden in 1920. 



aristata. England in 1907. 



' Communicated in a private letter from Dr. A. B. Borthwick, of Scotland. 



* The statements concerning occurrences in North America arc based on records and specimens in Uie 

 Office of Investigations in Forest Pathology. 

 '■ Private letter from W. Stuart Moir, Office of Blister-Rust Control. 



