CHAPTER XXIII 



LARCH DISEASES 



The three native species of larch or Larix are important 

 forest-trees in northeastern and northwestern United States. 

 The eastern and European larch are frequently used as orna- 

 mentals. The eastern larch is commonly affected by several 

 wood- and root-rots. Of these, the pecky wood-rot and red- 

 brown sapwood-rot are most destructive. The leaf-rusts are 

 rare. In the Northwest, the larch is not only subject to sev- 

 eral wood- and root-rots but is also seriously damaged by a 

 dwarf mistletoe which causes large swellings and witches'- 

 brooms. The seedlings are often killed by a fungus which 

 causes a- root-rot. 



Seedling Root-Rot 



Caused by Rhizina undulata Fries 



Seedlings of the western larch are killed by this root-rot 

 in northwestern Uiiited States. It may be found also in some 

 northeastern states since the fungus is known to occur in this 

 region. The diseased roots of seedlings from three to six years 

 old are matted together by an abundant growth of white my- 

 celium. The fruiting-bodies of the pathogene are formed on 

 the surface of the ground. They are dark brownish, undulat- 

 ing structures with a light colored margin when young. A 

 fuller description of this disease is given under hemlock diseases, 

 page 177. • 



Leaf-Rusts 



Caused by Melampsora Bigelowii Thtlm. and M. Medusas Thum. 



The needles of larch are sometimes affected by two similar 

 rusts. These diseases have been found in various localities 



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