64 PROTECTION OF PLANTS, 1915-16 



THE WHITE PINE BLISTER RUST IN CANADA 



W. A. McCubbin, Dominion Field Laboratory of Plant Pathology, 



St. Catherines, Ont. 



During recent years there has been a wonderful increase in the exchange 

 of commodities of all kinds between parts of the world which were formerly 

 more or less isolated from each other, and among the innumerable articles 

 that are thus freely passing back and forth across the world are large num- 

 bers of seeds, bulbs, seedlings, and nursery plants. The readiness with 

 which insects and fungus diseases can be carried on these seeds and plants, 

 and thus become established in a new country, has been increasingly evident; 

 so that nearly all progressive countries now find themselves compelled to 

 adopt strict quarantine methods in order to protect themselves from the 

 virulent diseases of other nations, or of other continents. In Canada we 

 have already learned by several unfortunate experiences that it is far more 

 profitable to keep a disease out than to attempt to eradicate it after it has 

 become established within our borders, and as time goes on, and fresh 

 dangers of the same kind appear, the value of learning this lesson well is 

 becoming more and more apparent. 



Among the latest nuisances that have been imported here from other 

 lands is one that hails from Europe, where it has been a well known pest 

 for many years. It is the White Pine Blister Rust (Peridermmm strobiKleb.) 

 As the common name indicates, it is chiefly noted as a fungus parasite 

 of the white pine (Pinus strobus L.) but it can also attack several other 

 species of pines, viz: — P. cemhra, P. monticola, P. excelsa, and P. lamher- 

 tiana, and perhaps any or all of the thirteen species of five-leaved pines. 

 It may be noted in passing that the five-leaved pines alone are susceptible, 

 and that the two- or three-leaved species, including the Austrian Pine, the 

 Scotch Pine, and the Jack Pine of our northern forests, are not subject to 

 the disease. 



The most serious phase of injury from this disease on the White Pine 

 occurs in the seedling stage. It is believed that the fungus gains entry by 

 some wound in the twigs or branches, and from the point of entrance it 

 grows rapidly up, down and around the branch in the soft outer bark. 

 In a short time the branch or stem is girdled and the part above the 

 affected area dies. The presence of the fungus in the tissues causes a 

 considerable swelling of the limb, and this swelling often takes on a 

 sickly yellowish appearance. Once established the fungus progresses down 



