UNITED STATES 

 DEPARTMENT OF AGRICULTURE 



Miscellaneous Publication No. 273 



Washington, D. C. 



Issued February 1938 

 Slightly revised April 1939 



INSECT ENEMIES OF WESTERN 

 FORESTS 



Compiled by F. P. Keen, senior entomologist, Division of Forest Insect Investiga- 

 tions, Bureau of Entomology and Plaiit Quarantine 



CONTENTS 



Introduction 



Kinds of forest insects and the losses they 



cause 



Direct losses 



Indirect losses 



Relation of insects to forest management 



Determining causes of forest-tree damage 



Insects affecting seed production 



Key to diagnosis of insect injury to cones 



and seeds 



Cone beetles 



Cone moths 



Cone maggots 



Cone borers •. 



Seed chalcids 



Nut and acorn weevils 



Acorn moth 



Insects injurious to seedlings in nursery or 



forest 



Key to diagnosis of insect injury to seed- 

 lings 



White grubs 



Root vi^eevils 



Wireworms 



Cutvforms 



Root bark beetles 



Root aphids 



Insects injurious to young trees (saplings and 

 poles) 



Page 



2 



2 



5 



Page 

 Key to diagnosis of insect injury to young 



trees 



Insects affecting tvv^igs, terminal shoots, 



and buds 



Sap-sucking insects 



Feeders on the inner bark of young trees. . 



Defoliators of young trees 



Insects injurious to mature forest trees 



Key to recognition of insect injury to ma- 

 ture trees 



Leaf feeders and defoliators 



Miners in the inner bark and phloem 



Insects injurious to wood and forest products. . 

 Key to diagnosis of insect injury to wood 



and wood products 142 



Insects working in unseasoned logs or lum- 

 ber 



Insects working in seasoned or decaying 



wood 



Insects injurious to forest range plants 



Natural control factors 166 



Climatic and environmental influences. . _ 166 



Natural enemies 169 



C ontrol of injurious forest insects 171 



Silvicultural control 172 



Biological control 173 



D irect artificial or remedial control 174 



Literature cited 197 



Index of host trees 202 



General index 205 



58 

 95 

 141 



143 



159 

 164 



1 For many years entomologists of the Bureau of Entomology and Plant Quarantine 

 engaged in the study of forest-insect problems have considered compiling the great mass 

 of records in their files so that it would be in more usable form. There has been a 

 growing need for a manual or handbook for use by forest rangers and others entrusted 

 with the administration of forest lands and the prevention of insect losses. Recently 

 the tremendous impetus given to forest conservation by the establishment of the Civilian 

 Conservation Corps camps has made insect control an actuality in many forests where 

 previously it had been impractical. This called for the instruction and education of 

 these men and of their leaders and has crystallized efforts toward bringing together the 

 material in this handbook. In compiling this manual all sources of information have 

 been drawn upon to make the presentation as comprehensive and up to date as possible. 

 Published bulletins, records in the files, unpublished work of field men, and previously 

 mimeographed manuals or instructions issued by the leaders of the forest-insect field 

 laboratories of the Bureau of Entomology and Plant Quarantine in the Western States 

 have been used as needed. It is obviously impossible to give full credit to all the workers 

 who have contributed to the making of this publication. F. P. Keen has taken the 

 initiative in its compilation, with the assistance of J. M. Miller, J. C. Evenden, and 

 J. E. Patterson, and, in fact, the entire technical personnel of the Bureau's western 

 forest-insect laboratories have contributed parts in their respective specialties. This 

 rnanual is restricted to the insects of the western forests, although the general discus- 

 sion and control methods are in a large measure applicable to any part of the United 

 States. It is planned to follow this with another manual covering the eastern forests. — 

 F. C. Craighead, in charge, Division of Forest Insect Investigations. 



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