CHAPTER VII 

 ASH DISEASES 



Several species of ash (Fraxinus) are common forest-trees 

 in most parts of the United States. White, green and black 

 ash are the important timber-trees. These are common 

 throughout eastern and central United States. The same 

 three species mentioned above are frequently used for shade 

 and ornament. 



Ash is exceptionally free from destructive diseases. The 

 rust of the leaves occurs sporadically and may assume an 

 epiphytotic nature. Little damage is caused to the trees, 

 however, unless defoliation occurs two or three years in suc- 

 cession. Several parasitic fungi cause leaf-spots on ash (see 

 page 29). Only one wood-rot is described as important in ash. 

 This disease is rarely found in the East but is destructive on 

 the western limits of the white ash. The slow growth which 

 the ash makes in that region seems to predispose the trees to 

 this disease. Where the trees grow more rapidly, they are 

 seldom affected. The roots of ash frequently are killed by 

 low temperature (see page 74). 



Leaf- and Twig-Rust 



Caused by Puccinia fraxinata (Link) Arthur 



The leaf- and twig-rust of red, green and possibly other 

 species of ash is striking because of its effect on the leaves and 

 twigs and its epiphytotic nature. It is common, at least in 

 eastern and central United States, but varies greatly in abuu- 



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