IV. INSECTS." 
UNITED STATES DEPARTMENT OF AGRICULTURE 
FARMERS’ 
BULLETIN 
Wasuincton, D.C. 674 Jury 8, 1915. 
Contribution from the Bureau of Entomology, L. O. Howard, Chief. 
CONTROL OF THE CITRUS THRIPS IN CALIFORNIA 
AND ARIZONA. 
By J. R. Horton, Scientific Assistant, Tropical and Subtropical Fruit Insect Investi- 
gations. 
INTRODUCTION. 
The citrus thrips,’ a minute orange-yellow insect, has in the past 
few years caused extensive damage to citrus fruits in the San Joaquin 
Valley of California and also occasioned considerable injury in 
southern California and Arizona orange groves. 
The nature and extent of the injury caused by this insect and its 
life history and habits were carefully studied, and extensive experi- 
ments for its control were conducted by the writer during the period 
from 1910 to 1912. It is the purpose of the present paper to give 
briefly the practical control measures resulting from these studies. 
INJURY. 
The citrus thrips is a sucking insect feeding on the plant juices 
of the leaves, the fruit rind, and the bark of tender stems, in much 
the same manner as the mosquito draws its food from its victims. 
For this reason the insect can not be killed by stomach poisons 
sprayed on the plant, but must be controlled by sprays that kill 
by contact. 
The injury caused by the citrus thrips begins with the seedling 
orange tree. The leaves are scarred and distorted, and to a certain 
extent the stock is devitalized. When the seed stock is budded and 
the foliage of the seedling trimmed off, the thrips attacks the bud. 
Nursery buds will make a fine, luxuriant growth of 2 or 3 feet in a 
1( Euthrips) Scirtothrips citri Moulton; order Thysanoptera, family Thripide. 
Notre.—This bulletin is of interest to the citrus growers of the Pacific coast and the Southwest. 
92706°—Bull. 674—15 
