U. S. D. A., B. E. Bui. 80, Part IV. D. F. 1. 1., September 1, 



PAPERS ON DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



THE PEAR THRIPS AND ITS CONTROL.* 



(Euthrips pyri Daniel.) 



By Dudley Moulton, 



Engaged in Deciduous Fruit Insect Investigations. 



INTRODUCTION. 



Cultivation and spraying, the principal treatments involved in the 

 control of the pear thrips, are largely subject to suitable weather con- 

 ditions, and each, to be effective, must be accomplished at its proper 

 time. Other orchard work, such as irrigation, cultivation, pruning, 

 and spraying for other insect and fungous troubles, must therefore be 

 considered well beforehand and completed or so arranged that nothing 

 will interfere with the treatment for the thrips. It is highly impor- 

 tant that the individual orchardist should have everything in readiness 

 to treat his own orchard at exactly the right time. Preparedness for 

 and thoroughness in the work of spraying and in plowing, it will be 

 found, are the most important factors in the successful control of this 

 insect. 



DISTRIBUTION. 



The pear thrips is known to occur only in the central part of Cali- 

 fornia, and especially in localities in the general neighborhood of the 

 San Francisco Bay. Reports of its ravages have been received from 

 the Sierra Nevada foothills, near Newcastle and Auburn, and from the 



a The control of the pear thrips has been for several years the principal problem 

 confronting the growers of deciduous fruits in portions of central California. This 

 insect, on account of its mode of attack and habits, has presented unusual difficulties 

 in control. It is believed, however, that the investigations of the Bureau of Ento- 

 mology have now determined practical and efficient measures which, if carefully 

 followed out by orchardists, will insure its reduction below injurious numbers. The 

 investigation has involved a large amount of detailed study of the insects' behavior 

 on the trees and in the ground, and the testing of a large series of spray mixtures, fer- 

 tilizers, soil fumigants, etc. Mr. Moulton has been continuously engaged in the work 

 for the past three years, assisted a part of the time by Messrs. Charles T. Paine and P. R. 

 Jones. Beginning with the spring of 1909, Mr. S. W. Foster was charged with the 

 operations in Contra Costa County and northward, Mr. Fred Johnson collaborating dur- 

 ing the spring months. The present is the second report upon the pear thrips, the first, 

 published as Part I of Bulletin 68 of this Bureau, dealing largely with the insect's life 

 history and habits. — A. L. Quaintance. 



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