UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 957 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. 
PROFESSIONAL PAPER 
February 6, 1922 
INVESTIGATIONS OF THE WHITE-PINE BLISTER 
RUST. 
By Perley Spaulding, Pathologist, Investigations in Forest Pathology. 
CONTENTS. 
Scope of the investigations 1 
Origin and distribution of Cronartium ribi- 
cola 3 
Hosts of Cronartium ribicola 11 
Pines infected and likely to becom 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 16 
Susceptibility of Ribes species and varie- 
ties to Cronartium ribicola 23 
Life history of Cronartium ribicola 24 
The Peridermium stage on pines 24 
The Cronartium stage on Ribes 40 
Overwintering of Cronartium ribicola 68 
Important dates in the life history of Cronar- 
tium ribicola 72 
Control of the white-pine blister rust 73 
Significant factors which determine con- 
trol 73 
Experiments in control in Europe 76 
Experiments in control in North America * 80 
Status of the control of white-pine blister 
rust 89 
Literature cited 90 
SCOPE OF THE INVESTIGATIONS. 
In a previous publication (131) 1 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 
ri Europe since the appearance of this earlier publication. At various 
imes since 1911 some of the more salient results of the investigation 
f Cronartium ribicola Fischer and the disease caused by it have been 
-ublished (132 to 148, 180). During the years 1915 to 1919, inclu- 
clusive, publication has fallen far behind the investigations. 
1 The serial numbers in parentheses refer to " Literature cited" at the end of this bulletin. 
46103- 21— Bull. 957 1 
