FUMIGATION INVESTIGATIONS IN CALIFORNIA. 
INTRODUCTION. 
Early in July, 1907, the writer received a commission to investi- 
gate the use of hydrocyanic-acid gas in the control of insect pests 
of citrus trees in southern California. Acting under detailed instruc- 
tions from Mr. C. L. Marlatt, the Assistant Chief of the Bureau of 
Entomology of the United States Department of Agriculture, be 
spent the latter part of July and the following three mouths in a 
thorough field investigation to acquaint himself with the condi- 
tions of citrus culture throughout southern California, the distribu- 
tion of the different citrus pests and the damage caused by them, 
the existing methods for their control, and the status of fumigation 
as then practiced in the various citrus districts. During this period 
all the important citrus-producing sections south of Santa Barbara 
were visited, and local conditions were carefully examined. This 
work was greatly facilitated by the hearty cooperation of the differ- 
ent county horticultural commissioners, who gave their time 1 freely 
and greatly assisted the writer in becoming familiar with all the 
features of the problem in their respective counties. 
The writer desires to acknowledge his indebtedness to the many 
people who have assisted him during this investigation and facilitated 
the progress which has been made. To Mr. C. L. Marlatt, Assistant 
Chief of the Bureau of Entomology, he is especially indebted for 
valuable assistance and advice. It is also the writer's great pleasure 
to acknowledge his appreciation of the work of Mr. Frederick Maskew, 
who has most capably assisted him in the performance of many of 
his experiments. Mr. Maskew also prepared several of the illus- 
trations used. To the Hon. J. W. Jeffrey, State commissioner of hor- 
ticulture of California, credit is due not only for his activity in paving 
the way for this investigation but also for the able support given 
since field work was commenced. To Mr. William Wood, of Whittier, 
CaL, the writer acknowledges his indebtedness for assistance in intro- 
ducing the improved system of fumigation in the region adjacent to 
Whittier, as well as for practical advice with regard to citrus insects 
and their control, a subject about which he is especially well informed. 
This occasion is also taken to thank the various horticultural officers 
of southern California, packing-house managers, and the many citrus 
growers who have assisted and supported this investigation. 
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