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CIRCULAR 8 6 9, U. S. DEPARTMENT OF AGRICULTURE 



One type of closed warehouse, the idea for which was developed 

 by the Stored Tobacco Insect Laboratory of this Bureau, has been 

 adopted by several firms. The walls are of sheet metal over a wooden 

 frame. The joints of the metal are locked and sealed with a calking 

 compound. Ventilators and doors close against gaskets, so that the 

 storage can be quickly and easily sealed for fumigation. Such a 

 building is shown in figure li. A similar, but more substantial, ware- 

 house can be constructed of cinder block, cement block, or brick. 



i 



Figure 14. — A metal-clad, closed-type tobacco warehouse, especially designed to 

 facilitate fumigation. Note the ventilators on the side and roof. 



SPACE SPRAYS 



Pyrethrum-oil sprays are more effective against the tobacco moth 

 in closed-type warehouses than in open storages. The systematic 

 use of space sprays against the adult moths as a preventive measure 

 has proved more efficient and cheaper than fumigation in protecting 

 the tobacco from damage by this insect. Sprays also aid in holding 

 down a cigarette beetle infestation and may decrease the number of 

 fumigations required. In some infested warehouses spraying has 

 given satisfactory control of the cigarette beetle. However, spray 

 does not penetrate the tobacco and kill the young stages of the insects, 

 whereas fumigant does. Against well-established infestations spray- 

 ing is no substitute for atmospheric fumigation. The adult moths 

 and most of the adult beetles emerge from the tobacco to mate in the 

 open, where they can be killed with spray. Unfortunately a small pro- 

 portion of beetles do not emerge, and in heavy infestations this num- 

 ber is sufficient to keep the infestation going. 



The recommendations for the use of pyrethrum-oil spray in open- 

 type warehouses apply also to closed-type storages. 



WAREHOUSE FUMIGATION 



For effective control of insert> by warehouse fumigation, the build- 

 ing must be adequately sealed. All openings in the walls, floors, and 



