CHAPTER XVIII 

 FIR DISEASES 



The firs are important forest-trees of western and north- 

 eastern United States. The balsam and Fraser fir are the only 

 native species in the East. Several species are common in the 

 West. The Douglas spruce or fir of western United States is also 

 considered in this chapter for convenience. Many native and 

 exotic species of fir are extensively used as ornamentals through- 

 out the country. 



The word " fir " is properly restricted to the genus Abies, 

 with erect cones and flattish leaves, and the word "spruce" 

 to the genus Picea with cones mostly becoming pendulous 

 and keeled leaves. The red fir or Douglas spruce is of the 

 genus Pseudotsuga. 



Fir is particularly subject to diseases of the wood. Many 

 of the wood-rotting fungi which attack fir are also equally de- 

 structive to pine, spruce, larch and hemlock. The root-rots 

 common to conifers also cause considerable damage to fir 

 wherever it grows. In western United States the dwarf mistle- 

 toes seriously deform the fir. Besides these important dis- 

 eases, the fir is occasionally affected by leaf blister-rusts, leaf- 

 cast, rust witches'-broom and the gray mold twig-blight. These 

 diseases are limited in their distribution by various environ- 

 mental and host relations. 



Leaf Blister-Rusts 

 Caused by species of Uredinopsis, Pucoiniastrum and Calyptospora 



Several very similar blister-rust diseases of the needles of 

 fir (Abies and Pseudotsuga) are found in the United States. 



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