REPORT OF THE SECRETARY. 117 



WORK IN THE ORANGE AND LEMON GROVES OF CALIFORNIA AND 



FLORIDA. 



One important investigation of the Bureau was completed with the 

 close of the last fiscal year, namely, the study of the problem of 

 hydrocyanic-acid gas fumigation in California directed against cer- 

 tain scale insects on citrus trees. The problem was attacked from 

 all points of view, with the prime idea of increasing the efficiency of 

 the process, which had previously been carried on in a wasteful and 

 unscientific w^ay, and of reducing its cost. It has been shown as a 

 result that the extremely satisfactory increase in the efficiency of 

 the process, brought about by the careful experimental work carried 

 on, has in itself greatly reduced the cost, since one treatment under 

 present methods is as lasting in its effects as three or four distinct 

 treatments under old methods. A practical man in southern Cali- 

 fornia, himself a large gainer through the results of this investigation, 

 and who closely watched the Bureau's experts at their work, informs 

 the Department that at least S250,000 has been saved to his 

 region. 



The work on the white fly in Florida has been carried on, and the 

 principal efforts of the year have been with insecticides and spra3dng 

 methods as adapted to Florida conditions. It has been found that 

 by careful application of l^nowledge gained by studies of the life 

 history of the white Ay the cost can be reduced to two-thirds during 

 late spring, while other experiments have shown that the cost can 

 safely be reduced about one-half during the summer months on 

 account of the greater susceptibility of the insect in the conditions 

 in which it is to be found at that season. All efforts to adapt native 

 parasites of allied insects to the citrus white fly having failed, and 

 Congress having authorized a search for the foreign parasites of this 

 destructive species, an expert agent has been sent abroad upon this 

 important search and at latest advices was in India, which has been 

 supposed by naturalists to be the original home of the white fly. 



In my last annual report I called attention to a new insect enemy 

 of the orange, in the shape of a thrips, which punctures the rind of the 

 fruit, making it scabby and reducing its value. The same insect 

 also injures the young leaves. An investigation of this insect has 

 been carried out through the year, and large-scale experiments have 

 been made with various sprays, some of which have been found to be 

 successful. Unfortunately there is a series of generations of the 

 insect throughout the year, which renders two or three spray appli- 

 cations necessary. The Bureau has especially introduced spraying 

 methods, and a large number of power sprayers have been purchased 

 and extensive operations begun under the advice and immediate 



