THE TOBACCO BEETLE. 17 



ALTERNATIONS OF HEAT AND COLD. 



Experiments made with infested tobacco indicate that the effective- 

 ness of cold in killing different stages of the beetle can be increased 

 by alternations of heat and cold. Sudden and extreme changes in 

 temperature seem more destructive to the beetles than longer ex- 

 posures to moderate cold. This method is applicable also to cold- 

 storage treatment of infested tobacco. 



EFFECT OF HEAT ON DIFFERENT STAGES OF THE TOBACCO BEETLE. 



It has been found that adults of the tobacco beetle become inactive 

 after a few minutes' exposure to heat above 117° F., but recover 

 unless, for a considerable length of time, the temperature is kept 

 higher than 120°. An exposure of one hour at temperatures between 

 140° and 150° proved effective in killing all stages of the beetle. The 

 time required for treatment depends upon the quantity and charac- 

 ter,bf the mateci^l. A temperature of from 125° to 140° F., con- 

 tinued for a few hours, or of 150° for a short time, has been found 

 effective under ordinary conditions. 



EFFECT OF HEAT DURING THE PROCESS OF MANUFACTURE. 



" ..Tests made in tobacco factories have shown that the temperatures 

 reached during certain processes of manufacture are sufficiently high 

 to sterilize the tobacco quickly and effectively as it passes through 

 the driers.^ Reinfestation of the finished product depends on the 

 methods of packing.'handling, and storing. 



THE USE OF STEAM IN STERILIZING TOBACCO. 



While steam furnishes, under some circumstances, an effective and 

 convenient means of sterilizing empty storage rooms or ware- 

 houses, numerous difficulties prevent its use in sterilizing infested 

 tobacco. If leaf tob-icco is exposed to steam at high temperatures 

 for any length of time it becomes more brittle, the texture of the leaf 

 and the aroma are changed as the natural oils are drawn out, and the 

 color becomes darker. Notwithstanding the general prejudice against 

 steaming, however, there seems to be considerable evidence that mild 

 steaming may be employed to advantage in treating certain classes of 

 cigar tpbacco, and the process is said to have been used to a consid- 

 erable extent. A convenient method of steaming cigar tobacco in 

 revolving drums, with the steam under pressure of about four atmos- 

 pheres, is said to have been used successfully in the Philippines.^ In 



^ Several tests sho^^ed that a temperature of about 180° F. was reached. 

 'The rhilippine Journal of Science, v. 8, no. 1, 1913. 



