398 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



diseases. This work, carried out in cooperation with the Bureau of 

 Plant Industry, has been successful and the results have been 

 brought together for a publication on the subject. Two new oil 

 emulsions have been tested which give much promise as treatments 

 not onh^ for insects attacking citrus, but also for those attacking 

 deciduous trees. Experiments in the use of dusts for the control 

 of the orange rust mite have been completed and the results have 

 been published in the local horticultural press. A j^aper giving 

 results of several years' study of the rust mite is in course of prepara- 

 tion and will prove of much value to citrus growers. Further data 

 on the biology of the Florida red scale have been accumulated and 

 it is believed that these studies will soon permit of a complete 

 account of this very important citrus pest. 



The continued importance of the citrus thrips in California led 

 to the establishment of a laboratory at Lindsay in cooperation 

 with the Tulare County Citrus Growers' Exchange for a special 

 investigation of this insect. Attention is being given to the biology 

 and ecology of the citrus thrips, and extensive experimental work 

 in the jfield with various spra}^ materials is being done to test their 

 relative efficacy. Since this station was established in March, 1923, 

 there has not been sufficient time for definite results in the biologic 

 or field experimental work. The indications are that spray ma- 

 terials in general use on citrus will, when applied in the proper 

 manner and at the proper time, be effective in the control of the citrus 

 thrips. Spraying for the thrips, however, must be considered in 

 conjunction with spraying for other insects, such as the Citricola 

 scale. Since the cost of spraying amounts to about $10 to $15 per 

 acre for a single application, and since probably two applications 

 for both scale and thrips control are about the maximum that can 

 profitably be given, special attention will be directed to the develop- 

 ment of economical and effective methods for the control of the 

 two pests by one and the same treatment. Further experiments 

 with nicotine dusts for the control of the thrips confirm earlier 

 conclusions that this was not effective. 



Fruit flies in Hawaii, — The investigations and control of fruit 

 flies in Hawaii have been continued in cooperation with the Federal 

 Horticultural Board. The plant quarantine regulations of the 

 board require the inspection of fruits and vegetables for shipment 

 to the mainland, and supervision over plantations and packing 

 sheds is maintained. In connection with this work 2,330 shipments 

 of fruits and vegetables for export to the United States have been 

 inspected and 670 packages, mostly bunches of bananas, were re- 

 jected as unfit for shipment. The number of packages certified 

 for shipment was as follows: 215,555 bunches of bananas, 11,304 

 crates of pineapples, 5,659 crates of taro, 389 bags of coconuts, 

 149 crates of ginger root. As heretofore, daily records of parasitism 

 of the Mediterranean fruit fly, Ceratitis capitata^ by the four in- 

 troduced parasites haA'e been made, as well as the amount of infes- 

 tation by the fruit fly in different host plants. Much progress 

 has been made in the life history studies of three bruchids, Bnwhus 

 prowpis^ Mylahris sallaei^ and CaryoboTu^ gonagra^ all of which 

 attack the seed pods of the algaroba, Prosopis julifoi''a. Several 

 parasites attack these bruchids, four species of which were in- 

 froflnrpd into the island from Texas. These parasites are being 



