INDUSTRIAL FUMIGATION AGAINST INSECTS 



47 



excess of these fumigants in order to counteract losses by absorption 

 and leakage and to insure a continuously saturated atmosphere. In 

 experimental work it has been found that a dosage of 1 pound of either 

 flake naphthalene or paradichlorobenzene to each 100 cubic feet of 

 space will cause fabric pests to cease feeding and to die after prolonged 

 storage in tight rooms. 



When no attempt is made to hasten evaporation by the application 

 of heat, the vapors of naphthalene and paradichlorobenzene are not so 

 quickly toxic to insects as are the liquid fumigants. Their chief value 

 lies in the continuous protection that they afford. Since vapors are 



Figure 35. — Rug-storage vault in which rugs are protected against fabric pests 

 by vapors of paradichlorobenzene or flake naphthalene. 



evolved but slowly from the crystals, one application may last for 

 several months. 



Light concentrations of the vapors of naphthalene and paradi- 

 chlorobenzene have an irritating effect on the eyes and respiratory 

 tract, making a person who has been exposed to them more susceptible 

 to colds and other respiratory ailments. Higher concentrations are 

 toxic and must be avoided. 



Dried Fruit 



Dried fruit is very susceptible to insect attack and must be pro- 

 tected from infestation at all times. Growers and packers usually 

 find it necessary to fumigate dried fruit before it is stored, and for 

 this purpose should equip themselves with fumigation chambers or 

 fumigable storage bins (fig. 3). The fumigation of dried fruits un- 

 der rubberized tarpaulins is reasonably effective. The fruit can be 

 fumigated and then placed in an insect-tight storage section, or it 

 can be placed directly in storage bins that are so constructed that 

 they can be fumigated from time to time as needed. Any type of 

 construction that is gastight is suitable for storage bins. 



On ranches (figs. 25 and 26), where the fire hazard can be guarded 

 against, carbon disulfide can be used. It is both cheap and effec- 



