8 FUMIGATION FOR THP] CITRUS WHITE FLY. 



During the last few years certain nurserymen in Florida have made 

 use of fumigation against the white fly with good success, treating, 

 for the most part, small-sized trees. Other parties have tested fumi- 

 gation on trees of all sizes, but, for lack of adequate equipment or of 

 a knowledge of the most economical methods of procedure and dosage 

 requirements, have not continued. 



In January and February, 1907, the writer, aided by Mr. Stephen 

 Strong, formerly horticultural commissioner of Los Angeles County, 

 Cal., specially appointed in this Bureau as fumigation expert, and 

 Mr. A. C. Morgan, special field agent, temporarily transferred from the 

 cotton boll weevil investigations, conducted careful experiments in 

 Orange County, Fla., in order that fumigation for the white fly might 

 be placed upon a practical basis. Modern California methods as 

 adapted to all sizes of trees were employed and the principal results 

 are embodied in the present bulletin. 



In December, 1907, and January, February, and March, 1908, 

 fumigation experiments were continued by the Bureau of Entomology 

 on a larger scale, testing the conclusions drawn from the work of the 

 j^revious winter and extending the investigation to cover the ground 

 more thoroughly. In this work the writer was assisted throughout 

 the season by Messrs. W. W. Yothers and E. A. Back, and during the 

 month of January Mr. II . S. Woglum was also engaged in the work. 

 Altogether nearly 4,000 trees have been fumigated in Florida in 

 this experimental work, under the immediate supervision of the 

 agents of the Bureau of Entomology. It is too early to include in 

 this bulletin more than the general results of the past winter's experi- 

 mental work, but the text has been made to conform to these 

 results as far as worked out. 



There remain many details concerning the fumigation process which 

 have demanded investigation, and at the present writing these are 

 receiving attention by agents of this Bureau who are conducting an 

 exhaustive study of the matter in California. The present bulletin 

 aims to give the results of experiments in fumigation for the white fly 

 and such information and recommendations as are of immediate 

 value to those who may contemplate the adoption of fumigation as 

 a practice, or who may desire first to secure a small equipment in order 

 to become familiar with the methods of procedure. The directions 

 given herein are believed to be sufficiently detailed to enable any 

 orange grower to conduct fumigation, after a few preliminary tests, 

 without the assistance of experienced hands. The recently discovered 

 occurrence of the wlute fly in California increases the importance of 

 definite information concerning the requirements as to dosage. 



A new system for the estimation of dosage is recommended herein, 

 as it is believed that the usual method of judging concerning the dosage 

 requirements for scale-insects can not give the uniformity of results 

 which should be obtained in using this remedy against the white fly. 



