12 BULLETIlSr 783, U. S. DEPABTMEN-T OF AGEICULTXJKE, 



A steam pressure of from 75 to 100 pounds may be employed advan- 

 tageously. Since bags of compact material are heated to the center 

 with difficulty, so far as possible they should be separated before 

 treatment to facilitate uniform heating, for insects and their larvae 

 become more active upon the application of the heat and may work 

 their way to the center of the bags in their efforts to escape it. 



Better results may be obtained by providing the radiators with 

 water traps or vents. 



Rice and cacao beans should not be exposed to a temperature above 

 130° F. for more than one hour, as excessive splitting takes place in 

 rice, especially if bleached, and, owing to the excessively oily nature 

 of cacao beans, they may become rancid. 



Germination in the case of some seeds, such as peanuts, is not af- 

 fected even by an exposure of six hours to a temperature as high as 

 140° F., but it is best to be on the safe side in the treatment of com- 

 modities affected by this moth until we have had more experience 

 along this line. It should be added that a temperature of 140° F. is 

 fatal to most forms of insect life in a short time — ^larvae, pupse, and- 

 adults. The Indian-meal moth, it has been learned by experiment in 

 the Bureau of Entomology, dies in less than half an hour when so 

 exposed. 



FUMIGATION METHODS. 



HYDROCYANIC-ACID GAS. 



For the fumigation of buildings and other structures inhabited by 

 the rice moth, the hydrocyanic-acid gas process is the most useful. 

 Indeed, it is now the standard remedy for practically all insects 

 affecting stored products. It has been in use for this purpose for 

 about 20 years and most progressive millers are familiar with the 

 method of application. Information in regard to hydrocyanic-acid 

 gas fumigation has been furnished by the Bureau of Entomology in 

 various bulletins and other publications. In the earlier ones the use 

 of cyanid of potash or potassium cyanid was advised, but owing to 

 conditions brought about by the war it is now impossible to secure 

 this chemical, and as a result cyanid of soda or sodium cyanid is 

 being used, and while somewhat expensive, is much cheaper than the 

 corresponding potash salt. The formula is as follows : 



Sodium cyanid avoirdupois ounce 1 



Sulpliuric acid fluid ounces — 1^ 



Water do 3 



Information in regard to this method is furnished in Farmers' 

 Bulletin 699, " Hydrocyanic- acid Gas Against Household Insects." 

 While this, as the title shows, is especially for dwellings, the methods 

 advised can be adapted readily to mills and storehouses. 



