WHITE-PINE BLISTER RUST IN WESTERN EUROPE. 25 
matic conditions suitable to the growth of the five-needle pines were 
found favorable to the development of the blister rust. 
ECONOMIC ASPECTS OF THE BLISTER-RUST PROBLEM. 
The problem of controlling the blister rust in eastern North 
America is distinctly an economic one, and the practical application 
of forest pathology must aid in the protection of a basic industry 
by maintaining forest production. The task at present has developed 
beyond protecting merely a restricted area; it involves the entire 
country west as well as east. It has been positively demonstrated in 
eastern North Amer- 
ica that this disease 
can be controlled at a 
reasonable cost by up- 
rooting allcurrant 
and gooseberry bushes 
within 900 feet of 
white-pineforests. 
The blister rust can 
not be eradicated 
from North Amercia, 
but the local destruc- 
tion of currants and 
gooseberries prevents 
damage to pines 
within the control 
area. 
The value of the 
commercial eastern 
white pine alone 
amounts to $276,- 
000,000 7 an asset 
well worth insuring 
against the rust. Re- 
cent careful studies 
made on the rate 
Fig. 14.—Limber pine (Pinus flevilis) in the National 
of rea h Arboretum at Nogent sur Vernisson, France, dying from 
=P = d of the a blister-rust attack. The 12-year-old tree in the center 
fungus in New York, was much weakened in 1920, as indicated by the yel- 
T : a lowing and shedding of the needles, and died the fol- 
New Hampshire, V er- lowing year. This species appears to be a ready victim 
mont, and Massachu- to the rust. 
setts show 15 per cent 
general infection. This is only the beginning of the invasion, for 
the disease is comparatively young here, having been only 25 years 
in the country and not imported to any appreciable extent until 
1909. During the next decade it will gain impetus, spread with ever- 
increasing force, and impress its seriousness upon the public mind. 
The crux of the situation lies in the fact that the young white- 
pine growth which should become the commercial stands of the 
next 30 years will be severely hit. Clearly the control of the disease 
by the removal of currants and gooseberries in the East must be 
vigorously pursued. 
16 Estimate of the United States Forest Service. 
