DISEASES OF FOLIAGE, ETC. 33 



done, from a commercial viewpoint, consists only in the 

 cessation of annual growth. The timber already 

 formed remains available, unless destroyed by second- 

 ary, nonparasitic fungi. 



NEEDLE DISEASE OF WHITE AND RED FIR. 



A disease of young white and red fir kills all needles 

 except the youngest on the ends of the twigs, causing 

 them to turn reddish gray, and finally to drop off. The 

 green needles which remain on the ends of the twigs 

 give the almost naked tree a green outline. The lower 

 parts of the tree suffer most. In severe cases the dis- 

 ease results in almost complete defoliation. The fruit- 

 ing bodies of the fungus Lophodermium nervisequium 

 appear in long black streaks following the middle line 

 on the underside of the needles. 



TAR-SPOT FUNGUS. 



The fungus Rhytisma is occasionally found on the 

 leaves of Oregon maple (broadleaf maple). It takes 

 its name from the black, tar-like dots which are evenly 

 distributed over round, yellowish, slightly raised spots 

 of about the size of a nickel. The black dots contain 

 the very small fruiting bodies. If in great numbers, 

 these spots seriously interfere with the functions of the 

 leaves. 



NEEDLE FUNGUS OF LODGEPOLE PINE. 



The foliage of lodgepole pine, especially in stands 

 about the higher meadows of the Sierra Nevada, often 



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