4 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 
parties, including contractors, associations, county horticultural 
commissions, and private individuals, owned approximately 5,150 
tents on June 1, 1910, the date on which the securing of these data 
was completed. 
In order to ascertain the extent to which fumigation is now prac- 
ticed, as well as the tax which this procedure annually places on 
citrus fruit growers, a careful canvass of the different parties operating 
tents has been made. This canvass has resulted in showing that 
approximately 36,000 acres were treated during the year from July, 
1909, to July, 1910. Many fumigators gave the number of trees 
which they treated; others the acreage alone. The average orchard 
will approximate 90 trees to the acre, and in those cases in which 
estimates were returned in acreage alone, this number has been 
considered to comprise an acre. Wherever not known, the cost of 
fumigating a tree has been placed at 30 cents, which price ap- 
proximates very closely the cost of fumigating the average-sized 
citrus tree in California. Calculated on this basis, the cost of fumiga- 
tion of the citrus orchards of southern California during the season 
1909—1910 approximated 81,000,000. 
THE VARIOUS SYSTEMS OF FUMIGATION. 
Each of the citrus-fruit-producing counties of southern California 
has a board of horticultural commissioners consisting of three mem- 
bers whose duties are to supervise the destruction of insect pests, 
plant diseases, and noxious weeds within their respective counties. 
In the three greatest citrus-fruit-producing counties— Los Angeles, 
Riverside, and San Bernardino — numerous inspectors are also 
employed to assist in carrying on this important work. As a matter 
of convenience the counties are usually divided into three districts, 
each of which is supervised by one of the commissioners. If inspectors 
are employed, usually each is allotted a limited portion of one of 
these districts, and is held responsible for the proper control of pests 
therein. He advises when the trees shall be fumigated, and, after 
arranging for the execution of the work, is supposed to see that it is 
properly carried out. There are several different systems under 
which the work may be done. 
BY CONTRACT. 
The larger part of fumigation is carried out under the contract 
system. Individuals or firms that possess complete equipment for 
commercial fumigation and practice fumigation as a business, enter 
into an agreement with the grower, who desires to have his orchard 
treated, to do the work for a certain sum. The rate is seldom uni- 
form but varies with such factors as the character of the ground, t he- 
acreage, and the size and arrangement of trees. Usually the cyanid 
