WHITE-PINE BLISTER RUST. 7 
not so much in the total number of diseased trees present as it does 
instances that the writer has had an opportunity to investigate per- 
sonally and where the origin of the spores has been determined. Two 
instances, on the other hand, where no diseased pines were found, 
seem to indicate that the aeciospores were blown long distances, 
though this is by no means a certainty. In the three instances exam- 
ined by the writer in 1913, the Ribes were about 100 feet from the 
diseased pines. There is every reason to believe that the uredo- 
spores of the white-pine blister rust may be blown half a mile or 
more. 1 
GENERAL RESULTS OF INSPECTIONS. 
Some of the general results of the annual inspections made for the 
white-pine blister rust, beginning in 1909 and continued to the pres- 
ent time, are of interest. In the States north and east of Washington, 
D. C, about 4,000,000 white pines are known to have been imported 
since 1900. Probably 500,000 more have been privately imported, 
about which nothing is known, making a total of about 4,500,000 
trees imported into these States. Of this number 1,725,000 are 
known to have been destroyed before they reached the hands of pri- 
vate individuals, leaving 2,775,000 which have been set out in lots 
ranging from 500 to several hundred thousand trees. The number 
of such known lots is approximately 200. The inspection of these 
trees has varied much, some having been inspected once, some care- 
fully inspected for the first time in 1913, and still others carefully 
inspected each year since the discovery of the disease on pines 
in this country in 1909. The figures given in Table I cover only 
those plantations that have been continuously under inspection from 
the beginning. 
Table I. — Results of the continuous inspection of infected lots of white-pine trees. 
No. 
Item. 
Number. 
Total trees inspected 
Total trees found diseased 
Total trees found with fruiting bodies of the fungus (data available for but 560,000 trees). 
Lots of trees inspected 
Lots of trees where disease was found 
Lots of trees where fruiting bodies of the fungus were found 
910,000 
8,177 
150 
88 
45 
In Table I, item 6 includes none of the lots counted in item 5, and 
the same is true of items 2 and 3. The same is also true of similar 
items in Table II. 
In considering these results it must be remembered that a single 
tree with fruiting bodies of the fungus and in proximity to a currant 
bush may start an epidemic of the disease which may continue for 
years and may spread over an area of several square miles. In fact, 
this is practically what happened at Geneva, N. Y. The danger lies 
1 Stewart, F. C, and Rankin, W. H. Cronartium ribicola and the proscription of Ribes nigrum. 
(Abstract.) In Phytopathology, v. 3, no. 1, p. 73. 1913. 
