INSECTS INJURIOUS TO STORED GRAINS 187 



Application. It may be applied directly to the infested grain 

 or seed without injury to its edibleness or viability by spraying 

 with an ordinary watering-can having a fine rose nozzle. In 

 moderately tight bins it is more effective, however, as it evaporates 

 more slowly and diffuses more evenly, if placed in shallow dishes 

 or pans, or on bits of cloth or cotton waste distributed about on 

 the surface of the grain or infested material. The liquid volatil- 

 izes rapidly, and, being heavier than air, descends and permeates 

 the mass of grain, killing all insects and other vermin present. 

 The bin should then be covered with boards, canvas, or blankets, 

 and allowed to remain at least twenty-four hours. If to be used 

 for seed, it should not be left for over thirty-six hours; but if not, 

 leave it forty-eight hours, which will do it no injury for food 

 After treating keep the grain covered to prevent reinfestation. 



Amount to Use. It was formerly recommended that the bisul- 

 fide be applied at the rate of 1 to 3 pounds to 100 bushels of grain 

 or 1000 cubic feet of open space. Recent experiments, however, 

 have shown the total inadequacy of this dosage. Experiments 

 made by Hinds and Hunter* show that the effectiveness of the 

 gas is in direct proportion to the temperature. Below 60 F. the 

 fumigation is ineffective and inadvisable. A dosage which will 

 kill practically all the weevil at 67 to 70 will kill but 60 to 70 per 

 cent at 60 to 65. They recommend the use of 5 pounds per 

 1000 cubic feet where the room or bin is quite tight and the tem- 

 perature is 70 or above. For open rooms and lower tempera- 

 tures, the dosage must be largely increased and may not be profit- 

 able. The above estimates are based upon the grain being in a 

 cubical shape; if it is spread out shallow, more bisulfide will be 

 necessary. 



Caution. " Certain precautions should always be observed. 

 The vapor of carbon bisulfide is deadly to all forms of animal 

 life if inhaled in sufficient quantity, but there is no danger in 

 inhaling a small amount. The vapor is highly inflammable, 

 but with proper care that no fire of any kind, as, for example, 

 a lighted cigar, lantern, or light of any kind, be brought into 

 the vicinity until the fumes have entirely passed away, no trouble 

 will be experienced." 



Hydrocyanic Acid Gas. Mills and storehouses which needed 



* Hinds and Hunter, Journal of Economic Entomology, Vol. Ill, p. 47: 

 R. I. Smith, Bulletin 203, N. C. Agr. Exp. Sta. 



