276 



MANUAL OF TREE DISEASES 



rant or goosebeny bushes In order to continue the cycle of de- 

 velopment. Spores are then produced throughout the summer 

 on these plants which cause the infection of other goose- 



berries and currants. In the autumn 



another type of spores (teliospores) is 

 developed on the affected currants and 

 gooseberries and from these are formed 

 basidiospores which cause the infection 

 of the young branches of five-needled 

 pines. The distribution of this fungus 

 on the pines, therefore, is dependent on 

 the presence or absence of gooseberries 

 and currants, and if present the amount 

 of damage done is somewhat dependent 

 on their abundance. Unfortimately sev- 

 eral species of these plants occur as 

 common weeds practically throughout 

 the range of the five-needle pines in the 

 United States. 



Symptojns. 



The young leaf-bearing twigs are in- 

 fected and the mycelium grows in the 

 bark and may extend into the larger 

 branches and trunks. The affected bark 

 is usually swollen^ but the tissue remains 

 normal and healthy in appearance for 

 two or three years. In the second or 

 third spring after infection occurs, the 

 prominent fruiting-pustules of the fungus 

 appear on the bark (Figs. 52 and 53). 

 These blister-like pustules are irregularly 

 Rg. 52. -Blister-rust on hemispherical or elongate, one-eighth to 

 twig of white pine. one-half inch across and orange-colored. 



