2 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



INTRODUCTION 



Protecting forests from destruction is the first basic requirement 

 in the practice of forestry. Important destructive agencies include 

 not only fire but also insect pests, fungous diseases, animals, drought, 

 flood, and wind. While damage from insects to timber is less spec- 

 tacular than that caused by either fire or wind, timber losses from 

 any of these three agencies may be of catastrophic magnitude. More- 

 over, insects are constantly at work in the forest and are the cause 

 of a steady drain on timber supplies. To allow fire or insects to run 

 unchecked in our forests is to invite disaster and serioush^ to threaten 

 the present and future timber supply. 



Protection from fire has been given intensive study, and notable 

 progress has been made in fire control. Less attention has been given 

 to the control of timber-destroying insects, partly because practical 

 control methods have not always been available and partly because 

 the expense of applying them has not been warranted in view of cur- 

 rent timber values. Moreover, practicing foresters in the West have 

 been handicapped by lack of a convenient reference manual, and as 

 a result have considered insect control a specialized subject with 

 which onh" the entomologists were prepared to deal. With the new 

 emphasis on forest conservation, there is, however, an increasing 

 demand by foresters for information on insects, as this information 

 is intimately related to man}?- phases of forest protection and man- 

 agement (fig. 1). 



Forest insects other than tree-killing species also present many 

 special problems. They may be encountered in every operation, from 

 the collection of seed through the planting, growing, and harvesting 

 of forest trees, in the handling and protection of utilized wood prod- 

 ucts, and even in the management of grazing lands. In all of these 

 cases some special knowledge of the insects concerned and of their 

 habits is required in order that suitable methods of prevention or 

 control may be effectively applied. 



This field handbook has been prepared to meet this need. The dis- 

 cussions are limited to the insects and the problems which they raise 

 in the management and protection of the forests of the Western 

 States, although the general principles of control are applicable to 

 other forest regions as well. It is hoped that the information assem- 

 bled will aid timber owners and foresters in recognizing the work of 

 important western forest insects, in applying suitable control meas- 

 ures, or in adjusting forest practices so as to reduce losses from this 

 source to the lowest possible point. 



KINDS OF FOREST INSECTS AND THE LOSSES THEY 



CAUSE 



All forests are swarming with insect life. This insect population 

 serves many functions and is as much an essential part of the com- 

 plex association of living, growing, and dying organisms which we 

 call the forest as are the trees themselves. 



Of the thousands of insect species found within our forests, many 

 are harmless or even beneficial. A great many feed on dead trees and 



