324 INSECTS AFFECTING VEGETATION 



for injury and contribute to a perpetual supply of vigorous, healthy 

 timber to be utilized before it passes the stage of profitable increment. 



PREVENTION OF INJURY TO DYING AND DEAD TREES. 



A large percentage of the injury to the wood of insect, fire, and 

 lightning killed trees and those killed or dying from injuries by 

 storms, disease, etc., can be prevented as follows : 



(1) By the prompt utilization of such timber within a few weeks 

 or months after it is dead or found to be past recovery. 



(2) By removing the bark from the merchantable portions of 

 the trunks within a few weeks after the trees are dead (the work to be 

 done either before or after the trees are felled). 



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



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

 will provide for the prompj, utilization of all trees which die from 

 any cause. 



PREVENTION OF LOSS FROM INSECT INJURIES TO NATURAL AND ARTI- 

 FICIAL REPRODUCTION. 



The successful control of the insects which destroy or prevent 

 the normal development of natural reproduction is a far more diffi- 

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

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

 preventing 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 

 orchard 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. 



PREVENTION OF INSECT INJURIES TO FOREST PRODUCTS. 



The problem of artificial control and prevention of insect inju- 

 ries to forest products offers less difficulties perhaps than that re- 

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

 control. 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 

 during a few weeks or months in the spring and summer, or during 

 the period when the particular species of injurious insects are flying, 

 are some of the conditions most favorable to attack. The period of 

 danger varies with the kind of timber and the time of the year it is 

 felled. Those felled in late fall and winter will generally remain 

 attractive to ambrosia beetles and adults of round and flat headed 

 borers during March, April, and May. Those felled during the pe- 

 riod between April and September may be attacked in a few days 

 after they are felled, but the period of danger from a given species 

 of insects may not extend over more than a few weeks. Thus cer- 

 tain kinds of trees felled during certain seasons are never attacked, 



