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 seciospores 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. 



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 



i 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. 



