CHAPTER XI 

 BIRCH DISEASES 



Many species of birch (Betula) occur as forest-trees in the 

 United States, especially in the northern parts. The native 

 species and imported varieties from Europe and Asia are 

 used extensively as ornamentals. 



The leaf-rust is destructive when birch and larch are grown 

 close together. The leaf-blister diseases and the several leaf- 

 spot diseases (see page 29) are not common and do very little 

 damage. Birch is, however, commonly affected by several 

 wood-rots, the most important of these being the powdery 

 sapwood-rot and common white wood-rot. The other wood- 

 rots are not so common and are restricted more or less to certain 

 species of birch. 



Leaf-Rust 



Caused by Melampsoridium betulce (Schum.) Arthur 



The leaves of various species of birch are sometimes affected 

 by this rust disease. It has been found in Massachusetts, 

 New York, Indiana and Washington and, therefore, probably 

 may appear in the northern states wherever birches and the 

 alternate larch hosts occur in proximity to one another. The 

 leaf-rust is not known to cause any great damage. 



Symptoms. 



Small, round, reddish-yellow pustules appear on the under 

 sides of the leaves in the summer. Later in the season a 

 second kind of pustule appears on the same leaves. These are 



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