FUMIGATION METHODS 



CHAPTER I 

 ECONOMIC USE OF HYDROCYANIC ACID GAS 



T"HHK discovery of the value of hydrocyanic acid 

 gas as an insecticide was due to the presence 

 of the cottony cushion scale in the citrous 

 orchards of California. This insect was un- 

 wittingly introduced into California from Australia. 

 For a time it seemed certain that the pest would ruin 

 the orange and lemon industry in spite of the con- 

 certed efforts of the most intelligent horticulturists to 

 combat it. Despairingly, the growers appealed, as a 

 last resort, to the United States Department of Agri- 

 culture for aid. The matter was taken up by the 

 Division of Entomology, and two assistants were 

 detailed by Dr. C. V. Riley, then Entomologist, to 

 undertake the study of methods for the control of the 

 insect. These assistants were D. W. Coquillett and 

 A. Koebele. To Mr. Coquillett belongs the credit of 

 first discovering the value of hydrocyanic acid gas, 

 now so extensively used, for the destruction of insects 

 and other animal pests. 



In addition to the detailed account of the gas treat- 

 ment given by Mr. Coquillett, in the report of the 



