200 MANUAL OF TREE DISEASES 



RrsT Witches'-Bkooms 



Caused by Gymnosporangium Nidttg-curis Thaxter, G. jitvenescens Kern 

 and G. Kernianum Bethel 



Three witches'-broom diseases are caused by sjjecies of 

 rust-fungi on different junipers. The first . species mentioned 

 above causes witches'-brooms of the red juniper in eastern and 

 central United States. The brooms are simply tufts of many 

 branches which are formed from the part of the parent branch 

 affected by the rust-fungus. The leaves of the brooms are usu- 

 ally of the pointed, awl-shaped, juvenile tj-pe. The second 

 species causes large brooms on the red and Rocky Mountain 

 juniper in the Rocky Mountains and in northwestern and nortii 

 central United States. The leaves of these brooms also are of 

 the juvenile type. The third species causes globose, compact 

 brooms on the Utah juniper in western Colorado. The leaves 

 on the brooms on this tree are scale-like. 



The life history of all three species is similar to the other rusts 

 of this type occurring on junipers and is discussed on page 192. 

 The spore-masses in the first species appear as linear cushion-like 

 brown masses bursting the bark of the affected branches, while 

 in the other two species they are small hemispherical brown 

 bodies, the size of a pin-head or smaller and arise from between 

 the leaves or in the leaf-axils. Various sptecies of service-berry 

 are the alternate hosts for these three species. The first species 

 is known to infect the quince also. 



Branch-Galls 



Caused by several species of Gynmosporangium 



Abrupt swellings of the stems of the various species of juniper 

 are often caused by species of the rust-fungi belonging to the 

 genus Gymnosporangium. Other species of the same group of 

 rusts cause cedar-apples and long fusiform branch-swellings, 



