OF WASHINGTON. 123 



it is in Florida, however, is shown by the fact that during the 

 dry season in Florida it receives a very notable check, and even 

 the most protracted Florida drought is characterized by condi- 

 tions of much greater moisture than the normal summer climate 

 of southern California. 



The fumigation project for southern California, under the 

 field direction of Mr. R. S. Woglum, has been undertaken by 

 the Bureau of Entomology in response to urgent demands from 

 horticultural commissioners of the principal citrus-fruit pro- 

 ducing counties of California and of many prominent growers. 

 From a million and a half to two million dollars are spent 

 every year in southern California in fumigating citrus trees, 

 and while the process has been in successful operation for 

 twenty years, it has never been scientifically investigated, and 

 imperfect results or direct injuries to trees are sometimes ex- 

 perienced, the reasons for which are not fully understood. 

 The purpose of the investigation of the Bureau is to standard- 

 ize the process ; in other words, to put it on an exact basis, 

 and increase its efficiency and limit its cost. The scope of 

 the work will cover (i) an investigation of the subject of 

 dosage, or the amount of gas necessary for the destruction of 

 different scale insects ; (2) the physiological effect on trees and 

 fruit; (3) the mechanical equipment, tents, and the methods 

 of handling them, and (4) life history and other studies of 

 the different insects involved. 



In recent fumigation a possible physiological effect on the 

 trees and fruit has been noted ; in other words, the gas has 

 seemed to show a distinct stimulating effect on the tree, re- 

 sulting in more abundant setting of fruit the year following 

 treatment. This result does not seem to have come from a 

 checking of the vitality of the tree which is shown in the case 

 noted ; on the contrary, a greater vigor in general appearance 

 as well as in the increased yield of fruit, and if true, this 

 stimulating effect will have a very important bearing on the 

 whole subject of fumigation. 



The white-fly work in Florida, under the direction of Dr. 

 A. W. Morrill, was found to be in a most satisfactory state of 

 progress. The life history of the species has been worked 

 out in the greatest detail by Doctor Morrill and Mr. E. A. 

 Back, and means of control are under elaborate investigation. 

 These are notably such natural means of control as the fun- 

 gous diseases and parasites, and the artificial control by fumi- 

 gation and insecticides. 



Fumigation seems to be the most promising means of arti- 

 ficial control. The conditions for fumigation for this pest in 



