CHAPTER XXV 

 MAPLE DISEASES 



Many species of maple occur in all p%rts of the United States. 

 They are important forest-trees in the eastern and central states. 

 Several of the native and a few exotic species are the most 

 widely used of any trees for shade and ornament. The maples 

 are of the genus Acer (including Negundo). 



In the forest the maple is seriously affected by the common 

 white wood-rot. Other wood-rots are also occasionally found. 

 Outside the forest, maples are subject to many diseases which 

 at times are important. Several species of fungi cause diseases 

 of the leaves which may "result in defoliation (see page 30). 

 Maples are also commonly affected by sun-scorch (see page 22). 

 The wilt disease has not been thoroughly investigated but is 

 known to have caused the rapid death of trees in several iso- 

 lated places. These diseases, together with the several wood- 

 rots, account to some degree for the commonly noted poor 

 condition of maples. 



Tab Leaf-Spot 



Caused by Rhyiisma acerinum Fries 



The large tar-like blotches on maple foliage are very con- 

 spicuous. The leaves which develop several spots are often 

 shed prematurely, and young nursery trees may suffer per- 

 manent injury from defoliation. In eastern United States 

 the red and silver maple are often attacked. In Europe the 

 Norway and Sycamore maple are commonly affected by the 

 same disease. In this country the Norway and Sycamore 



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