4 FUMIGATION INVESTIGATIONS IN CALIFORNIA. 
the moister coastal strip; for different seasons of the year: and for the 
different growing conditions of the tree, as whether in fresh leafage, or 
in bloom, or with different stages of the developing fruit. 
(2) Physiological effect on the tree and fruit. There is some evi- 
dence to show that the gas may have a stimulating effect on the tree. 
(3) Mechanical equipment. An important economical considera- 
tion in gassing is the employment of the most suitable tent cloths, and 
their treatment to give durability and imperviousness; also, the best 
mechanical means of hoisting tents over the trees. To be determined 
under this heading also are the most economical methods of generating 
the gas, and an indication of the quality of chemicals best suited for 
the purpose. 
In connection with this experimental work the scale species them- 
selves are being given a careful study in the field to determine their 
exact life history as a basis for the intelligent application of the 
remedy. 
This investigation was started in July, 1907, under the field charge 
of Mr. R. S. Woglum, who first made himself thoroughly familiar 
with the problem by a personal examination of conditions throughout 
the citrus-growing regions of southern California. The direct work 
of investigation began as soon as the fumigation season opened, and 
later Mr. Frederick Maskew was employed to assist in the work. The 
experimental work as planned has been conducted on a commercial 
scale, so that the conditions and results will be those normal to the 
ordinary care of citrus groves. To carry out all the lines of experi- 
ment indicated above, and the subsidiary ones which have developed 
in the course of the investigation, takes a good deal of time, and will 
probably occupy two or three years with the money and force now- 
available. Nevertheless, very considerable progress has been made, 
and the preliminary report herewith submitted covers the general 
features of fumigation procedure. 
Improved methods have been devised, and these are being very 
rapidly adopted throughout southern California. These improved 
methods make it possible to do much more uniform work and greatly 
simplify the method of estimating the proper dosage. Full advantage 
has been taken of the fumigation work conducted in Florida again-t 
the white fly under the field direction of Dr. A. W. Morrill, and the 
Morrill system of marking tents for the ready determination of dosage 
has been introduced, with modifications, into California. 
C. L. Maklatt. 
Entomologist and Acting Chief of Bureau in Absence of Chief. 
