UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 957 i 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



.JT^'^U-i. 



Washington, D. C. 



PROFESSIONAL PAPER 



February 6, 1922 



INVESTIGATIONS OF THE WHITE-PINE BLISTER 



RUST. 



By Perley Spaulding, Pathologist , Investigations in Forest Pathology. 



CONTENTS. 



Page. 



Scope of the investigations 1 



Origin and distribution of Cronartiuni ribi- 



cola 3 



Hosts of Cronartiiim ribicola 11 



Pines infected and likely to bccom e 



infected 11 



Inoculations of Cronartium ribicola on 



pines 12 



Species of Ribes that have been infected 



naturally 14 



Inoculations of Cronartium ribicola on 



Ribes 10 



Susceptibility of Ribes species and varie- 

 ties to Cronartium ribicola 2:? 



Life history of Cronartium ribicola 



The Peridermium stage on pines 



The Cronartium stage on Ribes 



Overwintering of Cronartium ribicola 



Important dates in the Ufe history of Cronar- 

 tium ribicola 



Control of the white-pine blister rust 



Significant factors which determine con- 

 trol 



Experiments in control in Europe 



Experiments in control in North America 

 Status of the control of white-pine bUster 



rust 



Literature cited 



Page 

 24 



24 

 40 

 68 



72 

 73 



73 

 76 

 80 



90 



SCOPE OF THE INVESTIGATIONS. 



In a previous publication (131)^ the writer collected data on the 

 more practical aspects of the white-pine blister rust, as presented in 

 European literature. 



Experience has shown that the white-pine blister rust has come to 

 North America to stay and that most careful and searching investi- 

 gations must be maintained to enable us to cope with it at all success- 

 fully. Investigations in Europe have been carried on in a desultory 

 way for 35 years. In North America they were begun less than 15 

 years ago. Really intensive work has been in progress for only 

 about 5 years. Considerable new experimental work has been done 

 in Europe since the appearance of this earlier publication. At various 

 times since 1911 some of the more salient results of the investigation 

 of Cronartium rihicola Fischer and the disease caused by it have been 

 published (132 to 148, 180). During the years 1915 to 1919, inclu- 

 clusive, publication has fallen far behind the investigations. 



1 Tho serial numbers in parentheses refer to " Literature cited" at the end of this bulletin. 

 4P103-21-Buil.SiJT-— 1 



