CHAPTER VIII. 



FOREST PROTECTION. 



INJURIES TO TREES. 



THE causes of injury to tree-growth are many and 

 various, some affecting principally the cultivated trees 

 in windbreaks and shelter-belts, and others affecting the 

 forest plantations and large areas of timber. Some injure 

 or destroy the trees or tree seeds, and others do damage 

 to the land on which they grow. 



Insects occasionally do an immense amount of damage 

 to forests, and it is often impracticable to combat them 

 successfully on a large scale. We must often, therefore, 

 depend on their natural enemies to hold these pests in 

 check. It is seldom, however, that insects of any one kind 

 are very abundant over a long series of years, but they 

 are occasionally nearly destroyed by the multiplication 

 of their parasites or other natural enemies. 



Saw-Flies and Tent-Caterpillars. At present perhaps 

 one of the most serious injuries to cultivated trees 

 results from the neglect to take precautions against leaf- 

 eating insects, such as saw-flies and tent-caterpillars. 

 These injuries may be largely prevented by the use of 

 Paris green in water applied by means of a force pump, 

 using it from a barrel carried in a wagon or on a stone boat. 

 An ordinary spraying nozzle should be used, with a suf- 

 ficient length of hose to reach up into the tree. In order 

 to reach the tops of the trees it may be necessary to have 



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