Insect Control Problem. 209 



seriously impaired by insect damage, and that much of this can be 

 prevented if greater interest is only manifested and the proper 

 precautions taken by the men who are directly responsible for the 

 administration of these forests, then the question of insect pro- 

 tection becomes vital. 



Before any National Forest can be brought to its maximum pro- 

 ducing capacity, we will have to know how to deal with those 

 insects which attack and kill living trees. As yet there has been 

 very little time to study or determine the damage caused by forest 

 insects. To bring the organization of the Forest Service to a 

 point where fire and trespass can be effectively handled has been 

 an enormous undertaking, but as we gain control of these two 

 essential features the need of protection against insects becomes 

 more and more prominent. 



There are a number of easily recognized differences between 

 forest fires and attacks by forest insects. Fires are always con- 

 spicuous. The smoke of even an incipient fire is visible from a 

 distance and is in itself a signal that help is needed. There is no 

 such evidence to announce the beginning of an attack by insects. 

 The red needles of the dead and dying trees are the first sign by 

 which the Ranger knows that a destructive agent is at work in the 

 timber. Forest fires start rapidly, burn fiercely and are ex- 

 tinguished in one season either by direct control or the advent of 

 the rainy season. Insect invasions start slowly, increase from 

 year to year, and, if allowed to continue unchecked, they are 

 brought under control by natural agencies only after a period of 

 years, usually not until a vast amount of timber has been killed. 



Fire damage is easily mapped and estimated. The annual 

 burned-over areas are computed with comparative exactness. 

 However, as much of the insect infestation is broken in distri- 

 bution and scattered over enormous areas, it cannot be easily 

 mapped and the amount of loss cannot be estimated without even 

 greater difficulty. 



Insect infestations, especially those caused by the more de- 

 structive species of bark beetles, can be classified into various 

 types or classes, just as fires are now grouped into different classes 

 according to their seriousness and the amount of damage. A 

 large local invasion of insects which kills thirty-five per cent, or 

 more of the trees on the infested area in one or two seasons 



