()8 
COLOKADO ExTEUI^IENT StATIOX 
is great danger of its being intro- 
duced into the Rocky Mountain 
forests at any time. The United 
States Department of Agriculture 
is spending great sums of money 
in an effort to prevent its further 
spread. The native stands of the 
sugar pine and the Western White 
pine in the western forests are 
valued at $240,000,000 Both of 
these trees are known to be sus- 
ceptible to the disease. If they 
once become infected there is little 
hope of controlling the disease un- 
less it is discovered soon enough to 
eradicate it before it becomes wide 
spread. 
The disease affects not only the 
five leaf pines but lives one stage 
of its life on the wild and culti- 
vated currants and gooseberries. 
Upon pines in early summer the 
rust causes irregular swellings in 
White pine blister rust. (After Stewart the bai*k. Ou the SWellillgS iu early 
and Rankin.) summcr white blisters are formed 
which later break open to set free a dust-like mass of bright yellow 
spores. Affected trees are eventually girdled and completely killed. 
The spores formed in the blisters on the pines are blown to cur- 
rant and gooseberry bushes on the leaves of which they form, first, 
small yellow spots which also contains spores. These spores spread 
the disease to other currant or gooseberry bushes. In late summer 
and autumn a second kind of spore is formed on the currant or goose- 
berry leaves and are seen as a brown hairy coating on the lower sui - 
face of the leaves. These spores cannot infect the gooseberry or 
currant bushes but are scattered to the pine which they infect, 
starting the disease anew. 
The only practical means of preventing loss from the white pine 
blister rust is to prevent its introduction into the Western states. 
Quarantine laws have been ]>assed to prevent the westward shipment 
of any white pines, gooseberries or currants. Quarantine laA^s, hov - 
