62 BULLETIN 737, U. S. DEPARTMENT OF AGRICULTURE. 



of imported cotton. This shows a degree of penetration beyond any- 

 thing likely to be found in the fumigation of hogsheads or bales 

 of leaf tobacco, or of cigars, or other classes of manufactured to- 

 bacco. The exposures found effective with vacuum apparatus in de- 

 stroying several other species of insects have not proved effective, 

 however, in destrojing all stages of the tobacco beetle. A series of 

 19 experiments with different amounts of sodium cyanid varying 

 from 1 ounce to 6 ounces per 100 cubic feet of space, with an expo- 

 sure of 1 hour and 45 minutes at a vacuum of about 25 inches ; and a 

 series of 14 experiments with 1, 3, and 6 ounces of sodium cyanid to 

 100 cubic feet of space, with an exposure of 2 hours and 30 minutes at 

 a vacuum of approximately 25 inches, did not show the process, 

 under the conditions specified above, to be more effective than fumi- 

 gation with the same dosages for 24 hours at normal air pressure. 1 

 All stages of the tobacco beetle were used in the experiments. These 

 were in baled cigar tobacco, in various classes of manufactured to- 

 bacco, and in pressed yeast cakes and tobacco refuse. The principal 

 advantage shown was the gain in time, as large quantities of manu- 

 factured tobacco can be quickly treated by the vacuum process. It 

 is thought that changes in the present method of vacuum fumiga- 

 tion will make the process better adapted to the treatment of to- 

 bacco. A repetition of treatment in the majority of instances will 

 be foimd necessary for complete sterilization. 



Fumigation with Carbon Disulphid. 



Carbon disulphid (CS 2 ) is quite generally used for the destruction 

 of the insect pests which infest grain, food products, etc., and has 

 been used extensively in control of the tobacco beetle. It is a color- 

 less liquid about one-fourth heavier than water, extremely volatile, 

 evaporating with great rapidity when exposed to the air. If the 

 temperature of the air is high and the evaporating surface large the 

 rate of evaporation is increased. In the liquid state it is inflammable, 

 but not explosive, and can be safely handled if the cans are kept per- 

 fectly tight and away from the fire. The vapor takes fire in the air 

 at about 200° F. under certain conditions. It is a violent and dan- 

 gerous explosive when mixed with air in the proportion of 1 volume 

 of vapor to approximately 14.3 volumes of air, in the presence of 

 fire of any kind, or at a temperature without flame of about 300° F. 

 The vapor is considerably heavier than atmospheric air. For this rea- 

 son carbon disulphid when used for fumigating should be placed at the 

 top of the fumigating compartment, if possible above the material to 

 be treated. Care must he taken not to inhale the fumes^ as the gas is 



An the above experiments the writer was assisted by Mr. H. L. Sanford, of the Federal 

 Horticultural Board, and by Mr. J. L. Webb, of the Bureau of Entomology. 



