58 CIRCULAR 3 6 9, U. S. DEPARTMENT OF AGRICULTURE 



1 pound of liquid hydrocyanic acid or its equivalent per 1,000 cubic 

 feet of space with an exposure of 24 hours will suffice for this pur- 

 pose. The warehouse should be prepared for fumigation in accord- 

 ance with the instructions given on page 6. 



VAULT FUMIGATION FOR FLOUR OR CEREAL MILL 



For the treatment of used bags, returned goods, or small lots of 

 infested flour or cereals, a fumigation vault is almost essential. The 

 vault can be of any of the types discussed on page 29. If possible, it 

 should be located in a building separate from the main mill, so that 

 used bags or returned goods can be fumigated before being taken 

 into the main building. 



Used bags can be fumigated successfully with any of the materials 

 recommended for vault fumigation, and at the same dosages. 



Bagged flour is fumigated with difficulty, owing to the excessive 

 absorption of the gas by the outer layers of flour. In vault fumi- 

 gations, when the vault is loaded to 25 percent of its capacity or 

 more, the dosage should be based on the weight of the flour to be 

 treated. A dosage of 12 ounces of liquid hydrocyanic acid or its 

 equivalent per ton of flour should be used for an exposure of from 

 24 to 48 hours if the temperature of the flour is 80° F. or above. 



For the fumigation of bagged feed or other milled cereals intended 

 for animal feeds, methyl bromide can be used at a dosage of 1 pound 

 for the first ton plus 2 ounces for each additional ton. 



VACUUM FUMIGATION OF FLOUR PRODUCTS 



For the vacuum fumigation of flour products at temperatures 

 above 70° F., it is recommended that 2 ounces of liquid hydrocyanic 

 acid per ton be used for an exposure of 3 hours with an absolute 

 pressure of 2 inches or less. The ethylene oxide-carbon dioxide 

 mixture can also be used successfully under the same conditions with 

 the following exposures and dosages: 3 hours, 10 pounds per ton; 6 

 hours, 4 pounds per ton; 12 hours, 3 pounds per ton. In all cases 

 the gas should be circulated for 15 minutes after it is introduced. 



For animal feeds, 4 pounds of methyl bromide per 1,000 cubic feet 

 of space for 3 hours or 3 pounds for 15 hours in filled vaults is 

 satisfactory. 



Rice 12 



Rice is grown and stored in the South, where it is subject to the 

 attack of many of the worst insect pests of stored cereals. It can, 

 however, be successfully fumigated with a wide variety of materials. 



For atmospheric fumigation the following dosages of materials 

 can be used per 1,000 cubic feet of space : Liquid hydrocyanic acid 

 or its equivalent, iy 2 pounds; chloropicrin, 2 pounds; methyl bromide, 

 1 pound ; ethylene dichloride-carbon tetrachloride mixture, 20 pounds : 

 or ethylene oxide-carbon dioxide mixture, 20 pounds. These dosages 

 are based on an exposure of 24 hours with the temperature of the rice 

 70° F. or above. 



Vacuum fumigation is particularly useful in the treatment of rice, 



12 Detailed information on the fumigation of stored rice will be found in TJ. S. Department 

 of Agriculture Farmers' Bulletin 1906, Insect Pests of Stored Rice and Their Control. 



