38 CIRCULAR 63 5, U. S. DEPARTMENT OF AGRICULTURE 



Although it is necessary to safeguard domestic tobaccos for export 

 during the storage period in this country, all lots of hogsheads or cases 

 suspected of containing infestation should be fumigated in vacuum 

 at the port, just prior to being loaded on the ship. This treatment at 

 the recommended dosage and exposure will kill all stages of the insects. 



ATMOSPHERIC CHAMBERS 



In many tobacco factories it is impracticable to install vacuum- 

 fumigation chambers, and the problems of factory fumigations are 

 handled satisfactorily in small atmospheric chambers. These vary 

 in volume and are constructed of the proper size to accommodate 

 the needs of the individual factory. 



Hydrocy anic acid is most often used in these chambers, and it may 

 be applied through copper pipes and nozzles in the same manner as 

 for large warehouses. This fumigant is applied also in the form of 

 sodium cyanide (fig. 21) or by means of discoids. The latter are 

 waferlike disks, made of wood pulp, in which liquid hydrocyanic 

 acid has been absorbed, each containing about one-half ounce of 

 hydrocyanic acid. These disks are packed and sealed in tin cans of 

 various sizes and marketed on the basis of the net contents of 

 hydrocyanic acid. 



Carbon disulfide may also be used effectively for the fumigation 

 of tobacco in small chambers. The dosage should be 10 pounds per 

 1.000 cubic feet of space with an exposure of 72 hours. Exposures 

 shorter than 72 hours are likely to produce unsatisfactory results. 

 The liquid carbon disulfide should be poured into shallow pans and 

 allowed to evaporate in the sealed chamber. This gas is highly in- 

 flammable and explosive in air mixtures and should be used only 

 under permit from fire insurance companies. The permit for the 

 use of this fumigant as endorsed by the Southeastern Under- 

 writers' Association is given on pages 30 and 31 of this circular. 



Calcium cyanide may be applied effectively in small chambers pro- 

 vided enough space is left between the stacked packages of tobacco 

 for spreading of the granular material. As stated on page 30 of this 

 circular, about 9 square feet of floor space are required to spread 

 1 pound of calcium cyanide properly. The dosage should be the 

 equivalent of 16 ounces of hydrocyanic acid per 1,000 cubic feet with 

 an exposure of 72 hours. This would require the use of 32 ounces 

 of high-grade granular calcium cyanide (50 to 55 percent of hydro- 

 cyanic acid) per 1,000 cubic feet. 



In the fumigation of tobacco in small chambers the bales should 

 have slats placed between them, and hogsheads and cases should not 

 be too closely stacked. This allows the gas to penetrate the tobacco 

 from all directions shortly after the start of the exposure. 



COST OF CONTROL METHODS 



Cost figures per unit weight of tobacco treated for insect control 

 are available for cigarette tobaccos only. In the periodic fumiga- 

 tion of closed warehouses with hydrocyanic acid gas the cost varies 

 somewhat according to the type of tobacco, whether flue-cured or Turk- 



