INDUSTRIAL FUMIGATION AGAINST INSECTS 



43 



At a temperature of 77° F., 8 ounces of paradichlorobenzene or 

 0.64 ounce of naphthalene is required to saturate the atmosphere in 

 1,000 cubic feet of space. Under ordinary storage conditions, how- 

 ever, it is advisable to use an excess of these fumigants in order to 

 counteract losses by absorption and leakage and to insure a con- 

 tinuously saturated atmosphere. 



When no attempt is made to hasten evaporation by the applica- 

 tion 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 evolved 

 but slowly from the 

 crystals, one applica- 

 t i o n may last for 

 several months. 



Aside from having 

 an irritating effect 

 upon the eyes, the va- 

 pors of naphthalene 

 and paradichloroben- 

 zene are apparently 

 not injurious to man 

 unless inhaled in 

 strong concentrations 

 for an extended pe- 

 riod. 



P a r a d i c h 1 o r o - 

 benzene crystalscan be 

 purchased for from 

 16 to 60 cents per 

 pound in small lots. 

 Naphthalene flakes 

 are quoted at 2y 2 to 

 10 cents per pound. 



DRIED FRUIT 



Figure 37. — Exterior view of commercial fur-storage vault 

 equipped for fumigation with ethylene dichloride-carbon 

 tetrachloride mixture. Note storage drum at right, 

 pump at left, and pressure tank in center connected 

 with various fumigating vaults, not shown, by pipe lines 

 on wall. 



Dried fruit is very 

 susceptible to insect 

 attack and must be 

 protected 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. 29 and 30), where the fire hazard can be guarded 

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

 tive. A dosage of 20 pounds per 1,000 cubic feet of space and an 

 exposure of 21 hours at a temperature of 70° F. or higher will give 



