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CIRCULAR 3 6 9, TJ. S. DEPARTMENT OF AGRICULTURE 



held in closed storage, fumigation with hydrocyanic acid gas is the 

 most effective means of preventing further loss from insect attack, 

 One fumigation a season should be sufficient to control the tobacco 

 beetle unless additional infested stocks are moved into the storage sec- 

 tion after the fumigation. If the tobacco moth is present, it will prob- 

 ably be necessary to fumigate 2 or 3 times during a season. Where 

 only one fumigation is given, a dosage of 1 pound of liquid hydro- 

 cyanic acid or its equivalent should be used per 1.000 cubic feet of 

 space, but if more than one is to be given, a dosage of 8 ounces is suffi- 

 cient. If possible, an exposure of from 48 to 72 hours should be given 

 in each instance. 



Figure 40. — Tobacco in bales and stacked as closely as shown here cannot be fumigated 

 satisfactorily by ordinary atmospheric fumigation. The bales should either be more 

 loosely stacked or removed to vacuum chambers for fumigation. 



For the fumigation of tobacco factories a dosage of 8 ounces of 

 liquid hydrocyanic acid or its equivalent per 1.000 cubic feet for a 

 period of 21 hours is sufficient. 



In order to keep down infestation in tobacco factories, many firms 

 make a practice of fumigating all incoming tobacco in airtight 

 vaults. For this purpose hydrocyanic acid in a dosage of 10 ounces 

 of liquid hydrocyanic acid or its equivalent, ethylene oxide at the 

 rate of 2 ^pounds, ethylene oxide-carbon dioxide mixture at 20 

 pounds, or carbon disulphide at 10 pounds, per 1,000 cubic feet of 

 space should be used for a period of from 48 to 72 hours. Carbon 

 disulphide should not be used unless the vault is isolated from the 

 rest of the buildings and the fire hazard can be controlled. The 

 fumio-ation of an entire tobacco Avarehouse with carbon disulphide 

 is a dangerous procedure and is not recommended. 



