10 MISSOURI AGRICULTURAL EXPERIMENT STATION BULLETIN 177 



It was in 1898 that it was first suggested that hydrocyanic-acid gas 

 could be used in mills, elevators and warehouses for the destruction of in- 

 jurious insects. 



Use up to the present time. Since the discovery of hydrocyanic-acid 

 gas as an insecticide it has been used in a number of different ways. 



1. To fumigate citrus trees infested with all sorts of scale insects. 



2. To fumigate deciduous fruit trees, including nursery stock, for the 

 destruction of San Jose scale. 



2. To fumigate deciduous fruit trees, including nursery stock, for the 

 destruction of San Jose scale. 



3. To fumigate greenhouses for the destruction of white fly, red spider 

 and other pests on greenhouse plants. 



4. To fumigate warehouses, elevators, mills and other buildings for the 

 destruction of various insect pests. 



Apparatus for fumigating car load lots: A tight oil canvas is placed 

 over the frames. The hydrocyanic acid gas is generated in a tank and con- 

 ducted through a pipe to the enclosure 



5. To fumigate dwelling houses, railroad coaches, street cars, hotels 

 and similar places for the destruction of lice, bedbugs, clothes moths and 

 household pests. 



The use of hydrocyanic-acid gas as a fumigating material is becoming 

 more extensive and the United States Department of Agriculture and all of 

 the state experiment stations recommend it. 



Method of using. The most general method practiced at the present 

 time in using hydrocyanic-acid gas is as follows: 



One fluid ounce of sulphuric acid having a specific gravity of at least 

 1.83 is poured into an earthenware crock, wooden bucket or tub, containing 

 3 fluid ounces of water. Into this mixture 1 ounce, by weight, of fused 

 cyanide of potassium, 98-99 per cent pure, is added. The above amounts are 

 used for every 100 cubic feet of space. In fumigating tender growing 

 plants, the above formula is too strong and has to be weakened. For dor- 

 mant trees, mills, elevators and the like the 1-1-3 formula is recommended 

 by both the United States Department of Agriculture and practically all of 

 the state experiment stations. 



In fumigating nursery stock an air tight box or house is necessary. 



