U. S. D. A., B. E. Rul. 99. Part I. D. F. I. I., March »!, 1911. 



PAPERS ON INSECTS INJURIOUS TO CITRUS AND OTHER SUBTROPICAL 



FRUITS. 



THE ORANGE THRIPS: A REPORT OF PROGRESS FOR 

 THE YEARS 1909 AND 1910. 



By P. K. JoNKS and .J. li. Horton." 

 Agents aiul Exiierts, Deciduous Fruit Insect Investigations. 



INTRODUCTION. 



The orange thrips {Euthrips citri Moulton), a small, yellow, active 

 insect belono-ino- to the order Thysanoptern (popularly known as 

 thrips), scars the fruit and curls and distorts the leaves of the orange. 

 At the present time its control constitutes the chief insect prob- 

 lem confronting the citrus growers of the San Joaquin Valley 

 orange belt of California, which winds along the Sierra Nevada foot- 

 hills, from east of Fresno to south of Delano. This insect, the work 

 of which was first noticed 15 or 16 years ago, has increased in num- 

 bers with the growth of the citrus industry and recently has assumed 

 serious economic importance. 



At the urgent request of a number of orange growers of Tulare 

 County, an investigation of the insect was begun the latter part of 

 April, 1909. The present paper is a preliminary report of the results 

 obtained during the seasons 1009 and 1910. 



Tlie writers Avish to acknowledge the financial assistance of the 

 Tulare County board of supervisors, the Lindsay Citrus Growers' 

 Protective League, and the Tulare County Fruit Fxchange; they 

 desire to acknowledge the kindness of Messrs. P. M. Baier, Harry 

 Postlethwaite, and R. H. Shoemaker in allowing the Bureau of Ento- 



''The investigation of the orange thrips by members of the force engaged iu 

 studies of deciduous-fruit insects appeared desirable, because these men were 

 familiar with a closely related species — the pear Ihrips — which is very destruc- 

 tive to prunes, pears, clierries, etc., in the San Francisco Hay region. However, 

 in order to keep together the articles dealing with insects damaging citrus and 

 other subtropical fruits, the present paper is published in a series of articles 

 dealing with insects of that class. — A. L. Quaintance, in Charge of Deciduous 

 Fruit Insect Investigations. 



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