260 EXPERIMENTAL FARMS 



1-2 EDWARD VII., A. 1902 



as the Poplar Rust [Melampsora populina, (Jacq.) Lev.], kindly identified by Prof. 

 L. P. Jones, of Vermont. Many apparently healthy trees were remarked in the month 

 of July to have very small and sparse foliage at the tips of the uppermost branches. 

 Subsequently these dropped their leaves and the foliage of many trees became yellow. 

 Later the rust developed conspicuously on the lower parts of Aspen trees, over a wide 

 area of territory. 



Mr. Geo. Batho, of the Xor'-]Yest Farmer, who is very observant of everything 

 affecting crops of all kinds, sent me specimens of diseased foliage in August last, sta- 

 ting that the rust had been exceedingly destructive to foliage of both poplars and 

 birches all through northern Alberta, the trees in many places being much disfigured 

 and stripped of their leaves. The fungus on the birch foliage proved to be Melamp- 

 sora betulina, (P.) Tul. Both the Aspen and the Birch referred to (Betula occiden- 

 talis, Hook.) are indigenous in the Xorth-west and are highly valued for planting as 

 ornamental trees on account of their compact growth and beautiful intense green foli- 

 age. In the arid country of the interior of British Columbia the beauty of the Aspen 

 is very striking, and. with the sturdy handsome Bull Pine (Pinus ponderosa, Dough), 

 forms one of the characteristic features of this part of the Dominion. The disease 

 was not observed west of the main chain of the Rockies, but was very apparent in 

 northern Alberta, and was exceedingly destructive to the foliage of the Cottonwood 

 (Populus monilifera, Ait.) at Brandon, Man. One row of young trees of this poplar 

 had been so severely attacked for two years running that most of the trees were dead 

 or in a moribund condition when Dr. Saunders visited the Experimental Farm at 

 Brandon in August. Specimens were sent off by him to my address in Ottawa, but 

 knowing that I was then absent in British Columbia, he sent specimens also to Mr. 

 Galloway, the Chief of the Bureau of Plant Industry at Washington, which were re- 

 ported upon by Mr. A. F. Woods, the Pathologist and Physiologist : — 



' I have borne in mind your request for information relative to rust of Populus 

 monilifera, and take pleasure in supplying the following data, furnished by our My- 

 cologist, Mrs. F. W. Patterson : 



' The disease is caused by the fungus Melampsora populina (Jacq.) Lev., and 

 occurs on various species of Populus in this country and in Europe. The uredospores 

 and teleutospores are found on the same leaves, the former causing the yellowing and 

 early fall of the leaves and the latter hibernating on the fallen leaves. The aeeidial stage 

 has not been determined with absolute certainty, but Rostrup demonstrated by experi- 

 ments that the teleutospores of Melampsora tremula?, Tul., which is now thought to be 

 synonymous with M. populina on Populus tremula, germinate on the leaves and shoots 

 of young pines, giving origin to C&oma pinitorquum. The seeidiospores from the pine 

 in turn produce the uredosporic and teleutosporic stages on the poplar leaves. Hartig 

 also proved that the same Melampsora causes Cceoma laricis on the needles of the 

 larch. These experiments, however, were made entirely upon foreign trees, and, so 

 far as our knowledge goes, cultures of spores of M. populina and infection experiments 

 with them in this country have been entire failures. 



' The Hatch Agricultural Experiment Station, Amherst, Massachusetts, has been 

 conducting experiments with fungicides on Populus nigra for several years, with a 

 view of preventing or controlling the disease. In the section in which the Hatch Sta- 

 tion is located, the fungus appears during the hot, moist weather of July and August, 

 and, when abundant and appearing at the earlier date mentioned, it kills many of the 

 branches, and the leaves become yellow and fall to the ground. 



' The uredo, or summer spores, are formed while the leaves are still on the tree, 

 end are soon scattered by the wind, causing the infection to spread with great rapidity. 

 Spores develop on the fallen leaves, and these spores, which are capable of living over 

 winter, upon coming into contact with new leaves in the spring or summer set up new 

 infection. 



