FUMIGATION FOR THE CITRUS WHITE FLY, AS ADAPTED 
TO FLORIDA CONDITIONS. 
INTRODUCTION. 
The discovery of tlio value of hydrocyanic-acid gas as an insecticide 
against citrus pests is properly considered one of the most important 
advances in economic entomology. This gas was first used by Mr. D. 
W. Coquillett, who in 1SSG was detailed by Dr. C. V. Kiley, the Ento- 
mologist of the U. S. Department of Agriculture, to experiment with 
insecticides against the cottony cushion scale (Icerya purchasi Mask.) 
in California. The process was afterwards brought to its present de- 
gree of usefulness through the extensive experiments of Mr. Coquillett, 
and is now generally recognized in the citrus-growing sections of 
California as the most practicable and efficient method of controlling 
the black, red, and purple scales. It is now used in combating citrus 
scales in South Africa, New South Wales, and elsewhere, with results 
so satisfactory that wherever it has once been tested it has proved its 
superiority over all other methods. 
In the eastern part of the United States Prof. H. A. Morgan 
conducted experiments with hydrocyanic -acid gas against citrus 
scales in southern Louisiana during the winter of 1892-93. Messrs. 
W. T. Swingle and II. J. Webber, of the Department of Agriculture, 
were the first to use this treatment against the white fly in Florida, 
conducting their experiments in February, 1894. In the winter of 
1900-1 901 , Prof. II. A. Gossard, then entomologist at the Agricultural 
Experiment Station of Florida, aided during a portion of his experi- 
ments by Prof. C. W. Wood worth, of the Agricultural Experiment 
Station of the University of California, undertook some experimental 
fumigation work against the white fly. The results were sufficiently 
satisfactory to lead Professor Gossard to the conclusion that the 
efficiency of this treatment against the white fly is such that if a 
fumigated grove were segregated from all others, one fumigation would 
render it so nearly clean that it would need no additional treatment 
for two or three years. It was predicted that a process that has been 
found so valuable in other parts of the world is certain eventually 
to come into favor in Florida. 
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