HEMLOCK DISEASES 183 



ish spots are produced on the leaves. Later reddish brown 

 pustules are formed (see page 298). Spores formed on the 

 dead aspen leaves the following spring, when blown to the 

 hemlock, cause the infection of the young green parts. 



The leaves and twigs affected by the second species, Necium. 

 Farlowii, may die in midsummer, the leaves falling off. When 

 defoliation does not take place, the infected leaves and twigs 

 bear reddish, swollen, velvety pustules in early spring. The 

 cones may show the same reddish bodies. 



Cause. 



These rust-fungi are close relatives of the hemlock blister- 

 rusts. The first species produces seciospores in open pustules 

 which do not have a bladdery covering, as in the blister-rusts. 

 The second species does not produce seciospores but forms 

 teliospores as its only spore-stage. These over-winter and 

 burst the epidermis, producing reddish waxy pustules in the 

 spring. The basidiospores produced by the germination of 

 the teliospores reinfect the young green parts of the hemlock. 

 Thus this rust-fungus requires no alternate host and occurs 

 only on the hemlock. 



Control. 



The rust having its alternate stage on poplar leaves may 

 be controlled by keeping poplars separated from hemlocks by 

 a few hundred feet. In the case of the second fungus, which 

 occurs only on hemlock, the affected twigs should be pruned off 

 in the winter and burned, thus destroying the spores of the 

 fungus and preventing further infection. 



Reference 



Ludwig, C. A. Notes on some North American rusts with Cseoma^like 

 sori. Phytopathology 6 : 273-281. 1915. 



