FUMIGATION FOR THE CITRUS WHITE FLY, AS ADAPTED 

 TO FLORIDA CONDITIONS. 



INTRODUCTION. 



The discovery of the 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 1886 was detailed by Dr. C. V. Riley, the Ento- 

 mologist of the U. S. Department of Agriculture, to experiment with 

 insecticides against the cottony cushion scale {leery a purcJiasi 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 H. 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 

 1900-1901, Prof. H. A. Gossard, then entomologist at the Agricultural 

 Experiment Station of Florida, aided during a portion of his experi- 

 ments by Prof. C. W. Woodworth, 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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