U. S. T). A., B. E. Bui. 68, Part I (Revised). D. F. I. I. Scptembt-r 'JO, 1909. 



PAPERS ON DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



THE PEAR THRIPS. 



(Euthnps pyn Daniel.) 



By DUDLKY MOULTOK. 



Engaged in Deciduous Fruit Insert Investigations. 

 INTRODUCTION. 



This paper brings too;ether the resiihs of an invest ijjat ion of the 

 Ufe history, habits, natural enemies, and methods of control of the 

 pear thrips (Euthrips pyri Daniel), a pest of deciduous fruit trees in the 

 San Francisco Bay region of California. The investigation was under- 

 taken at the request of the Santa Clara County board of supervisors, 

 who furnished the funds and liberally granted necessary facilities 

 for a thorough and scientific study, and was carried out in tlie Santa 

 Clara Valley, where the thrips seemed to be at its worst. The investi- 

 gation extended through a period of fifteen months, from February, 

 1904, to April, 1905." 



The writer offers this paper rather as an introduction for future work 

 than as a completed account, and it is intended especially for the fruit 

 grower, that he may understand the nature of the insect and its injurv\ 

 The alarm felt for the safety of the deciduous fruit industry, which 

 the pear thrips caused during 1904 and 1905, in the light of our pres- 

 ent knowledge need not again be experienced, and, altliough no effect- 

 ive means of control are jet offered, a knowledge of the life habits 

 should do much to clear away the uncertainty usually following the 

 first appearance of a destructive pest in any locality. 



OCCTTRRENCE AND DISTRIBUTION. 



The pear thrips is known to exist in the San Francisco Bay counties 

 and along the Sierra Nevada footliills, but it is not known how witlely 

 the pest is distributed outside of these localities. It is still a question 

 whether the insect is a native of California or an introduced form. 

 The pear thrips may have had some indigenous plant, such as the 



oThe writer wishes to acknowledge the work of Mr. Earl L. Morris and Mr. C. T. 

 Paine. He is indebted also to Prof. W. R. Dudley, head cf the department of sys- 

 tematic botany, and to Dr. G. H. Pierce, of the Leland Stanford Junior University, 

 for literature and helpful suggestions, and finally to Prof. Vernon L. Kellogg for his 

 ever helpful suggestions and encouragement. 



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