FOREST TREE DISEASES COMMON IN CALI- 

 FORNIA AND NEVADA. 



SCOPE OF THE STUDY. 



This manual, designed for practical use in the field, 

 discusses only the more important tree diseases found 

 in California and parts of Nevada, though most of 

 them are common also in other forest regions. Its aim 

 is to enable the field man to determine the cause of the 

 commoner diseases and injuries and to understand their 

 effect on the living tree. It discusses also ways and 

 means of control of fungi and mistletoes, as well as 

 climatic, biological, and soil conditions which bring 

 about diseases in forest trees. 



In studying forest tree diseases the object is of 

 course to learn how to fight and control them. For 

 success in this, however, we must at least know the 

 more common forms of the enemies we are to deal with, 

 how they act on the living tree, which organs they 

 attack, how they do it, and what the consequences are. 

 The simplest case of injury is destruction of certain 

 parts of the tree, when, for instance, a few needles are 

 browsed off by sheep or killed by needle miners or a 

 fungus. In such cases the tree will hardly suffer, and 

 there is no reason to speak of disease. If. however. 



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