188 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



treatment were formerly fumigated with carbon bisulfide, which 

 is still employed to a considerable extent, but this has been 

 largely replaced by fumigation with hydrocyanic acid gas, which 

 obviates the risk from fire. Directions for the use of this gas 

 should be obtained from the entomologist of the State Experiment 

 Station or from the Bureau of Entomology of the U. S. Depart- 

 ment of Agriculture. 



Sulfur Fumes. Professor R. I. Smith (1. c.) has made experi- 

 ments with sulfur dioxid, produced by burning sulfur slightly wet 

 with alcohol, and finds that it will effectively kill grain insects 

 but injures the germinating power of the grain. " It was found that 

 the fumes produced by burning 2J pounds of sulfur either in a 

 moist or dry atmosphere of 1000 cubic feet space, for twenty 

 hours, would kill all exposed adult insects and practically all the 

 young stages in the grain, but that this also destroyed its germinat- 

 ing power. . . While this treatment cannot be recommended 

 for general fumigation, there is no doubt of its being the easiest 

 and cheapest method of fumigating corn cribs, granaries and 

 similar places whenever they are being cleaned out and freed 

 of insects in preparation for the reception of more grain." 



Heat. The heating of grain was one of the earliest means 

 known of combating grain insects, but has been little used in this 

 country. Recently, however, Prof. Geo. A. Dean of the Kansas 

 Agricultural Experiment Station,* has shown that by super- 

 heating mills they may be rid of insect pests much more quickly 

 and cheaply than by fumigation, and with no risk from fire, or 

 from cyanide poisoning. His experiments show that if the 

 temperature surrounding an insect be maintained above 120 F., 

 with a normal amount of moisture, that in a very few minutes it 

 will be killed. This has become one of the most popular methods 

 of cleaning mills and may be used for small quantities of grain 

 where there are facilities for heating it or placing it in a super- 

 heated room, but probably carbon bisulfide fumigation will be 

 found more practicable for small amounts. 



* Geo. A. Dean, Journal of Economic Entomology, Vol. IV, p. 142 and 

 Bulletin 189, Kansas Agr. Expt. Station. 



