^ HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 
lottesville, Va. The same year it was first used in the treatment of 
nursery stock, and its development along this line has been so great 
and important that to-day in many States the fumigation of decidu- 
ous stock before it is planted is required by law. The use of hydro- 
cyanic-acid gas against insects affecting greenhouse plants has been 
successfully carried on for a number of years. Among the other 
important uses to which this gas has been successfully put are the 
treatment of mills, various other buildings, and stored products 
infested with insects. The ease with which this gas may be generated 
as well as its destructive power, greater than that of any other known 
insecticide, leads the writer to believe that as soon as the various 
uses to which this gas may be put have been thoroughly investigated 
and placed on a stable basis the future development of hydrocyanic- 
acid-gas fumigation will be quite as important and extensive as has 
been its past development. 
RECENT RENEWAL OF INTEREST IN FUMIGATION IN 
CALIFORNIA. 
The hydrocyanic-acid-gas treatment of citrus trees continued to 
become more widely used and to hold general favor with the fruit 
growers of southern California until about 1901, when the distillate 
spray was introduced. The treatment of trees with distillate was 
much cheaper than with hydrocyanic- acid gas. This fact, together 
with the fact that the distillate treatment was indorsed by many of 
the more prominent horticultural authorities and fruit growers led to 
its widespread use during the next few years. Simultaneously the 
introduction from South Africa of Scutellista cyanea Motschulsky, the 
parasite of the black scale (Saissetia olese Bern.), and its subsequent 
splendid showing led many people to abandon treating their orchards 
in the hope that this beneficial insect would hold the black scale in 
check. 
By 1903-1905 it had become very evident that the distillate spray 
had not only failed to keep the scales under control, but that its con- 
tinued use in many cases produced an injurious effect upon the tree 
itself. The Scutellista also had failed to control the black scale, 
although even a conservative must admit that its work has been of 
a most praiseworthy type. Spraying rapidly sank into disuse during 
1905 and 1906, until at the present time it has almost entirely given 
way to fumigation. The experience of the prominent fruit growers 
with the distillate spray has thoroughly satisfied them of the great 
superiority of the hydrocyanic-acid-gas treatment to that with a 
spray for scale insects on citrus trees. 
In the winter of 1903-4, Dr. G. Harold Powell, then of the Bureau of 
Plant Industry, United States Department of Agriculture, com- 
menced an investigatiop of the decay of oranges while in transit 
