24 BULLETIN 1186, U. S. DEPARTMENT OF AGRICULTURE. 
During the wet summer of 1917 (2, p. 24) the blister rust de- 
veloped so heavily and so seriously on cultivated black currants in 
England that nurserymen became alarmed and feared a decided 
setback to their currant crop because of defoliation of the bushes." 
A climatic cendition favorable to the spread of the rust on the 
currants results in an increased amount of pine infection. French 
Fic. 13.—Wimber pine (Pinus flexilis) growing in a nursery at Alnarp, Sweden. Blister 
rust first appeared here in 1920, at which time 100 seedlings 6 years old were de- 
stroyed. The young trees were growing within 300 feet of black currants and goose- 
berries. This shows the results that may be expected from an exposure of this species 
to the white-pine blister rust. 
foresters maintain that the disease is much more abundant during 
a wet year than in a dry one.* A _ similar opinion is upheld by 
members of the Belgian forest service. In the western United 
States the two factors of an abundance of wild currants and goose- 
berries and a climatic condition favorable to the fungus will work 
together to the detriment of the five-needle pines. European cli- 
‘ 14 Notes obtained from Kew Garden Laboratory, through the courtesy of Dr. A, D. 
‘otton. 
18 Oral statement to the writer, 
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