86 



FOREST PROTECTION 



mime chestnut species by crossing American chestnut with Japanese 

 varieties which are only slightly susceptible to the bark disease. 



3. White pine blister rust has already caused considerable damage 

 throughout the range of white pines in the East and Middle West, as 

 well as in the Northwest and Inland Empire. Large sums of money 

 have been appropriated by the Federal Government, by various states, 

 and even by private groups and individuals to combat the spread of 

 this disease. The fungus which causes white pine blister rust lives 

 alternately on various species of native and cultivated Ribes (cur- 



FIG. 45. The eradication of currant and gooseberry bushes to prevent the growth 

 and spread of white pine blister rust has been an important feature in State and 

 National Forests throughout the New England and Lake States, as well as in 

 the northern Rocky Mountains and other parts of the West. This fungus affects 

 northern white pine, western white pine and sugar pine. 



rant and gooseberry) and the five-needle pines. Control of this 

 disease in the East has proved to be both possible and practicable. 

 4. A large group of fungi are responsible for decay in living trees 

 and structural timber. Probably those fungi belonging to the family 

 Polyporaceae cause the greatest amount of damage. The Division of 

 Forest Pathology of the Bureau of Plant Industry in the U. S. De- 

 partment of Agriculture is actively engaged in studying and combat- 

 ing the diseases of forest trees, shade trees, and ornamental shrubs, 

 as well as the decay and discoloration of structural timbers and other 



