UNITED STATES DEPARTMENT OF AGRICULTURE 



DEPARTMENT BULLETIN NO. 1223 



Washington, D. C. T July 10, 1924 



THE EUROPEAN ELM SCALE IN THE WEST. 1 



By Frank B. Herbert," Scientific Assistant, Forest Insect Investigations, 

 Bureau of Entomologn. 



CONTENTS. 



Page. 



Introduction 1 



Importance ^_ 1 



History 2 



Synonymy 2 



Distribution and spread 3 



Injury 5 



Food plants 6 



Descriptions 6 



Life history and habits 9 



Seasonal history 11 



Natural enemies 12 



Control experiments 13 



Recommendations for control 15 



Summary ' IT 



Literature cited 18 



INTRODUCTION. 



The European elm scale, Gossy-paria spuria (Modeer), has long 

 been known in Europe and the Eastern United States as a serious 

 enemy of the elm. It was first discovered in the West in 1893, when 

 E. M. Ehrhorn found it infesting elms on the Stanford University 

 campus, Palo Alto, Calif. Prompt measures of eradication were 

 attempted, but were not entirely successful. Since that time it has 

 spread from this or other sources until it is now quite widely dis- 

 tributed throughout the West. It is becoming of considerable impor- 

 tance as a shade-tree pest owing to its distribution and to its par- 

 ticularly aggressive habits in newly infested localities. 



IMPORTANCE. 



The elm is probably the most popular shade tree in America. It 

 attains good size, produces a luxurious amount of green foliage, and 

 is planted throughout the United States and elsewhere in dooryards, 

 along streets, and in parks for shade and ornament. In the East 



1 Acknowledgments are due to- Dr. A. D. Hopkins, Forest Entomologist ; H. E. Burke, 

 Specialist in Forest Entomology; Harold Morrison, Coccidologist ; and otbers, for helpful 

 suggestions arid observations ; to W. S. Fisher, Specialist in Forest Coleoptera. for identi- 

 fication of the coccinellid predators : to S. B. Doten, Director and Entomologist of the 

 Nevada Agricultural Experiment Station, and to Frank N. Wallace, State Entomolcgist of 

 Indiana, for the use of a number of illustrations used in this publication. 



2 Resigned June 30, 1920. 



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