28 CIRCULAR S6 9, U. S. DEPARTMENT OF AGRICULTURE 



FUMIGANTS AND DOSAGE 



Several fumigants may lie used in vacuum fumigation of tobacco. 



Hydrogen cyanide is popular, particularly for cigarette tobaccos. 

 It is seldom applied on cigar tobaccos just prior to manufacture or on 

 cigars, because the odor may persist for several weeks. 



A 1 : 9 mixture of ethylene oxide and carbon dioxide is often used 

 for cigars and cigar tobaccos. Although it does not leave any objec- 

 tionable odor, it is not always effective, especially at temperatures 

 below 60 c F. 



Methyl bromide has been employed to a limited extent and is a good 

 insecticide, but obnoxious odors have developed in tobacco fumigated 

 with it. Furthermore, handling of tobacco fumigated with methyl 

 bromide may be very dangerous for several days after fumigation, 

 small quantities of absorbed gas being given off by the bales of tobacco. 



A 1 : 1 mixture of acrylonitrile and carbon tetrachloride has recently 

 become known as a tobacco fumigant. This gas is less dangerous than 

 methyl bromide or hydrogen cyanide, leaves no objectionable odor, is 

 an effective insecticide, and has not been known to injure tobacco. 

 However, it creates a fire hazard. 



Much tobacco is fumigated in vacuum during the fall, winter, and 

 spring, when the temperature of tobacco is below 70 c F. At such 

 temperatures it is necessary to increase the dosage of fumigant and 

 the results are erratic, perhaps because the insects are less active and 

 therefore more resistant. 



Exposure of infested tobacco to vacuum alone for practical lengths 

 of time is relatively ineffective in controlling stored-tobacco pests. 

 Tests showed that continuous exposure to a high vacuum ( above l >n 

 inches ) for 3 days killed all stages of the tobacco moth and all stages 

 of the cigarette beetle except the egg. An exposure of 10 days was 

 required to destroy the eggs of the beetle. However, even a 3-day 

 exposure is impractical under most conditions. 



The following dosages of fumigants are recommended for the 

 vacuum fumigation of tobacco at an exposure of 3 to 4 hours : 



Fumigant and type of>bacco: Poun(1s » er 1 - 000 cllVw * eet at ~ 



Hydrogen cyanide: ■"" *"■ or above 35° to 69° P. 



Flue-cured 4 a 



Turkish 4 5 



Cigar filler or binder 4 5 



Cigar wrapper 5 



Ethylene oxide-carbon dioxide: 



Cigar filler or binder 60 



Cigar wrapper 65 



Cigars 4o 



Acrylonitrile-carbon tetrachloride : 



Flue-cured 4 5 



Turkish 4 5 



Cigar filler or binder 4 5 



CONTROL IN TOBACCO FACTORIES 

 Preventing Infestation 



An important source of factory infestation has always been the 

 flight of cigarette beetles from storage warehouses nearby. The 

 various processe; — stemming, blending, bulking, handling, and manu- 



