INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 79 



(3) By felling the trees and placing the iinbarked logs in water. 



(4) By the adoption of a system of forest management which will 

 provide for the prompt utilization of all trees which die from any 

 cause. 



PREVENTION OF LOSS FROM INSECT INJURIES TO NATURAL AND ARTIFICIAL 



REPRODUCTION. 



The successful control of the insects which destroy or prevent the 

 normal development of natural reproduction is a far more difficult 

 problem than that presented by other classes of insect injuries, but 

 in this as in the others a great deal can be accomplished toward pre- 

 venting the reduction of future supplies. 



Much can be accomplished in nurseries and small plantations by 

 the adoption of the ordinary methods of controlling farm and or- 

 chard insects, but in the natural forests reliance must be placed 

 largely on systems of forest management which will bring about 

 unfavorable conditions for the work of the more important enemies. 

 (Hopkins, 1906c.) 



Utilization of Immune and Resistant Vaeieties and Races of Trees. 



Certain individuals representing varietal or racial forms of trees 

 of a given species are sometimes found to be either immune or de- 

 cidedly more resistant to the insects which are destructive or seri- 

 ously injurious to the life or wood of other individuals or varieties 

 of the same species. This fact suggests the importance of recogniz- 

 ing the well-known principle of improvement by selection. Thus, 

 selecting seed or cuttings from such immune and resistant trees^for 

 artificial propagation, or taking great pains to leave such trees in 

 commercial or selection cuttings for natural reproduction, will un- 

 doubtedly be an important step toward providing against damage 

 and loss in the future. (Hopkins, 19066, 190Ta, 1907c, 1907 d.) 



PREVENTION OF INSECT INJURIES TO FOREST PRODUCTS. 



The problem of artificial control and prevention of insect injuries 

 to forest products offers less difficulties perhaps than that relating 

 to many other branches of the general subject of forest-insect con- 

 trol. In most cases the principle of prevention is the only one to be 

 considered, since the damage is done soon after the insects enter the 

 wood, and therefore it can not be repaired by destroying the enemy. 



Crude Products. 



The proper degree of moisture found in the bark and wood of 

 newly felled trees, saw logs, telegraph poles, posts, and like material, 

 cut in the fall and winter and left on the ground or in close piles 



