320 MANUAL OF TREE DISEASES 



Cone-Rust 



Caused by Melampsoropsis pyroloe (DC.) Arthur 



, The young green cones of spruce are sometimes attacked by 

 this rust-fungus which occiu-s very commonly throughout 

 northern United States on species of wintergreen. The cones 

 of black, red, white and Engelmann spruce have been found 

 affected in northeastern United States and in Colorado. The 

 wide distribution of the same fungus on its other host, the 

 wintergreen, signifies, however, that it may be expected to occur 

 anywhere in northern United States from the Atlantic to the 

 Pacific. It is common in Europe also. Basidiospores from 

 over-wintering teliospores on the leaves of wintergreen infect 

 the green scales of the young cones in the spring and a few 

 weeks later roundish, whitish blisters burst through the epidermis 

 of the affected scales. Spores (seciospores) from these blisters 

 infect the leaves of wintergreen. The under surfaces of the 

 wintergreen leaves are often densely covered with the reddish 

 pustules of the urediniospores. The fungus can live over in 

 the persistent leaves of the wintergreen and thus the life history 

 may be carried on without the stage on the spruce cones. 



References 



Fraser, W. P. Cultures of heteroecious rusts. Mycologia 4 : 175- 



193. 1912. 

 Arthur, J. C, and Kern, F. D. North American species of Perider- 



mum. Bui. Torrey Bot. Club 33 : 403-^8. 1906. 



Rust Witches'-Brooms 



Caused by Peridermium coloradense (Dietel) Arthur and Kern, and P. 

 boreale Arthur and Kern 



These rust diseases, which often result in large witches'- 

 brooms, are common in the mountain regions of central western 

 and northwestern United States on Engelmann and Colorado 



