HITE-PINE BLISTER RUST may destroy much of the 
white pine of the United States. This destructive dis- 
ease probably had its original home in Asia, later reaching 
Europe. It was introduced into America during the years 
1898 to 1910. European and American investigations indi- 
cate that this rust can not spread direct from pine to pine 
and that an intermediate stage of development on currant and 
gooseberry bushes is necessary before it can harm the pine. 
Studies of the disease in this country showed that the dis- 
iance to which currant and gooseberry bushes infect pines 
is comparatively short. This knowledge is the basis of the 
local control work in the United States, which was begun 
experimentally in 1916. These experiments prove that un- 
der ordinary forest conditions in the eastern United States 
a stand of white pine is subject to little or no damage 
from the rust if there are no European black currants grow- 
ing within a mile and no other currant or gooseberry bushes 
within 900 feet. European black currants are dangerous to 
pine at greater distances than other species because they are 
more susceptible to the rust and produce a much larger 
volume of spores per unit of infected leaf surface. 
The purpose of the study in western Europe in 1919-20 
was to determine how destructive the blister rust had been 
to American white-pine species planted abroad and what 
steps, if any, had been taken to combat this disease in for- 
eign countries that would be of practical value in control- 
ling the disease in the United States. It was found that 
cultivated black currants and gooseberries, especially black 
currants, are very abundant in Europe and popularly con- 
sidered of more value than the foreign white pine. Conse- 
quently these bushes have not been removed from the 
vicinity of the white-pine plantations, and the blister rust is 
sradually driving these trees out of Europe by destroying 
such a large percentage that it is unprofitable to cultivate 
the species. White pine is being supplanted by other for- 
eign conifers, such as Japanese larch, Douglas fir, Sitka 
spruce, and Balkan pine. 
Very recently the blister rust has been found on the 
Pacific coast in Washington and British Columbia. This 
discovery is a matter of great concern, since there are 
seven different white-pine species in the West and the coun- 
try’s greatest white-pine resources are centered in the 
western white-pine and sugar-pine forests. Western white 
pine and limber pine apparently are more susceptible to the 
blister rust than eastern white pine. Sugar pine is also 
highly susceptible. To delay the spread of the rust through 
the eradication of cultivated black currants and quarantine 
enforcement and the development of practical local control 
measures adapted to the conditions found in western forests 
are the only alternatives to the ultimate extinction of the 
most valuable commercial pine-timber species of the West. 
39 WASHINGTON : GOVERNMENT PRINTING OFFICE : 1923 
