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



rial was effectively sterilized when exposed for 24 hours in a part 

 of the building where a temperature of 137° F. was reached, and 

 all stages of the beetle were killed. 



The tests made show that under certain conditions steam may be 

 used to advantage in sterilizing empty warehouses, as much higher 

 temperatures could easily be obtained than were reached in the ex- 

 periments. Dry heat, secured by fitting the building or storage 

 room with sufficient radiating surface, would, of course, be the most 

 practical means of heating, as steam turned directly into a room 

 for some time might cause injury to the building by expansion of 

 beams from moisture and heat combined. 



Other experiments have shown that temperatures of from 130° to 

 150° F. result in the death of all stages of the tobacco beetle, and it 

 is probable that very little if any damage to most grades of tobacco 

 would follow. In cleaning storage rooms, etc., live steam or hot 

 water applied through a flexible pipe fitted with a nozzle can often 

 be used to advantage in destroying the insects in refuse or dust 

 in crevices in the floor or walls. 



The expense of steaming in the foregoing experiment for 24 hours 

 amounted to $15.20, as follows : 



Engineer, 2 days @ $4 per clay $8. 00 



Fireman, 2 days @ $1 per day 2.00 



Fuel i. 4.50 



Water .70 



The expense of fumigating the same space (108,000 cubic feet) 

 with hydrocyanic-acid gas would have amounted to about $75, or 

 with carbon disulphid $60, these estimates being based on prices of 

 chemicals used for fumigation at the time of the experiment. 



USE OF STEAM AS A MEANS OE STERILIZING INFESTED TOBACCO. 



Although steam furnishes, under some circumstances, an effective 

 and convenient method of sterilizing storerooms or warehouses there 

 are numerous difficulties which prevent its use in sterilizing infested 

 tobacco. Leaf tobacco becomes more brittle if exposed to steam at 

 high temperatures for any length of time, the texture and aroma 

 are changed, and the color becomes darker. In spite of the general 

 objection against steaming, however, there seems to be considerable 

 evidence that mild steaming may be used to advantage in treating 

 certain classes of cigar tobacco. In the application of steam the 

 principal requisite is that the tobacco does not become too wet, and 

 that unnecessarily high temperatures are avoided. 



A method of treating cigar tobacco in revolving steam drums 

 has been tested in the Philippines (77). Steam was applied for 20 

 minutes at a pressure of about 4 atmospheres, the temperature rang- 



