PINE DISEASES 265 



soil to be matted together by white mycelium. Brown fruiting- 

 bodies are formed on the surface of the soil around diseased 

 trees. This fungus is more fully discussed under hemlock 

 diseases, page 177. 



Leaf Blister-Rusts 



Caused by fungi of the genus Coleosporium 



Several species of the genus Coleosporium grow in the needles 

 of pines, occasionally causing defoliation. These rust-fungi 

 require, in addition to the pine, some other kind of plant on 

 which to continue their life history. Such an alternation of 

 hosts is not uncommon in the rust-fungi. In the case of the 

 Coleosporium leaf-rusts of pine, seciospores are produced in 

 the yellow blisters pushed out from tlie pine needles. These 

 spores cannot reinfect the pine, but they may cause infection 

 of the leaves of certain near-by flowering plants. Here the 

 development of the fungus is continued and urediniospores 

 are formed. The urediniospores infect other plants of the 

 same kind and by a succession of several generations of these 

 spores the rust may become prevalent during the summer for 

 a considerable distance away from the pine which developed 

 the seciospores. In the autumn a brown layer of another type 

 of spores (teliospores) is formed on the plants which produced 

 the urediniospores. The teliospores germinate while they are 

 still attached to the host and minute basidiospores are formed. 

 These spores are short-lived and are blown about by the wind. 

 If they come into contact with the needles of the proper species 

 of pine, they may initiate a new infection. Thus the seasonal 

 life history of the fungus is completed. 



By eliminating the flowering plant, which must be present 

 for the fungus to complete its development, the rust is incapable 

 of existing. The minimum distance for the successful inter- 

 change of spores between the pine and the alternate host is 

 variable. Control is sometimes accomplished when all the 



