204 



TIMBER RESOURCES FOR AMERICA'S FUTURE 



Of 





I 



3-year moving mean 



10 



8,751,000 acres 

 (estimated) 



I'll 



J I 1 L 



I I I I 



I I I I 



'■II 



1935 



'40 



'45 



'50 

 YEAR 



'55 



'60 



Figure 76 



new diseases continue to appear. Since the turn 

 of the century, a large number of serious or 

 potentially serious diseases have attracted atten- 

 tion in this country. Some were inadvertently 

 introduced from foreign lands. The source of 



others is not known. StUl others have very likely 

 resulted from epidemic behavior of normally en- 

 demic diseases. A tabulation of some of the more 

 outstanding diseases regarded as new to this coun- 

 try since about 1900 is shown below. 



Species attacked 



Disease 



Chestnut blight Chestnut 



Blister rust 5-needle pines 



Phloem necrosis Elms 



Beech bark disease Beech 



Larch canker Larches 



Pole i>light Western white pine 



Birch dieback Birches 



Dutch elm disease Elms 



Littleleaf Shortleaf and loblolly pine 



Persin)mon wilt Persimmon do. 



Oak wilt Oaks and chestnuts do. 



Sweetgum blight. 



Sweetgum . 



Year first 

 reported ' 



1904 

 1906 

 1918 

 1920 

 1927 

 1929 

 1930 

 1930 

 1932 

 1933 

 1942 

 Unknown ^ 1951 



Cause 



Fungus 



do 



Virus 



Fungus and insect- 

 Fungus 



Unknown 



do 



Fungus 



-do 



' In some cases, notably oak wilt, littleleaf, and phloem 

 necrosis, the diseases were almost certainly present many 

 years before they were identified. 



2 A similar or possibly identical disease of sweetgum was 

 first reported in 1944. 



