acreages of forest susceptible to European gypsy moth in the 

 South, Midwest, Lake States, and West are not yet infested. 

 Despite quarantine measures, isolated infestations are frequently 

 found in these areas, the result of movement of infested outdoor 

 equipment or other articles from infested areas. Eradication 

 treatments are applied wherever isolated infestations are found, 

 for example in Georgia, Oregon, Utah, Washington, and 

 Wisconsin. 



The balsam woolly adelgid, first discovered in Maine in 1908, now 

 occurs widely in Canada and the United States. In recent de- 

 cades, it has killed large numbers of Eraser fir in North Carolina 

 (Witter and Ragenovich 1986). 



White pine blister rust, an introduced disease of pines, has severely 

 affected most of the valuable western white pine and, to a lesser 

 extent, the sugar pine resource. This disease was first discovered 

 in 1906 in New York State, and it subsequently spread through 

 the range of eastern white pine, causing significant damage 

 in some stands. The disease was found in western North America 

 for the first time in 1921 at Vancouver, British Columbia, and 

 subsequently spread widely in the Western United States. White 

 pine blister rust continues to spread to new areas. In 1990 the 

 disease was found for the first time in New Mexico, where it now 

 poses a serious threat to southwestern white pine. 



Dutch elm disease wa.s first found in 1930 in Ohio. This disease 

 now occurs throughout the United States. Large numbers of the 

 valuable American elm have been killed, significantly altering 

 many urban landscapes, and the disease continues to kill trees. 



Beech bark disease, first discovered in Canada, has spread from 

 Maine through the Northeast since the 1930's and has now 

 reached as far south as West Virginia (Houston 1987). The 

 disease results when bark attacked and altered by the introduced 

 beech scale insect is invaded and killed by fungi. As the disease 

 has spread, it has killed large numbers of American beech trees. 



Chestnut blight virtually eliminated the American chestnut as 

 a dominant tree species in the eastern forests during the early 

 1900's. American chestnuts were large, upper-canopy trees over 

 100 feet in height. When the chestnuts were killed, they were 

 replaced by other species, often oaks. Small chestnut trees still 

 grow from living root systems, but the sprouts are usually de- 

 stroyed within a short time by the blight. 



18 Forest Health Concerns 



