Storage Problems 



The tobacco industry, in general, has storage space available for a normal 

 inventory of leaf tobacco and of tobacco products. In some cases, however, com- 

 mercial storage space adapted for the handling of this commodity is used. ' Even 

 if the storage buildings are operated by the owner of the commodity, shipping 

 and sampling bring about the necessity for moving the tobacco into sections other 

 than those in which it was originally stored. Because of placing the tobacco in 

 these sections not previously fumigated, a considerable amount of sealing work 

 is necessitated, and as this must be done in a limited period of time, adequate 

 preparation in advance is often impossible. For this reason any development 

 that reduces the amount of labor required and speeds up the preparations for 

 fumigation is of considerable importance and aids in producing better results in 

 insect control. 



Sealing Methods 



Very little has been written on the subject of sealing closed-type tobacco-storage 

 warehouses for fumigation in connection with the control of insects. In an early 

 publication, the Bureau of Entomology and Plant Quarantine covered in some 

 detail the sealing of warehouse buildings. This information was later sum- 

 marized in Circular No. 635, Control of Insects Attacking Stored Tobacco and 

 Tobacco Products. In this publication, methods and materials currently used in 

 this type of work are briefly described. Recent studies of commercial fumigation 

 indicate the importance of adequate sealing and the need for an improvement 

 in methods and materials used in this work. 



Tobacco Insects and Their Control 



The Richmond Stored Tobacco Insect Laboratory (Bureau of Entomology 

 and Plant Quarantine) states that from South Carolina northward both the 

 tobacco moth (Ephestia elutella (Hbn.)) and the cigarette beetie (Lasioderma 

 serricorne (F.)) normally have from two to four generations a year. The time 

 of emergence of adults varies in relation to the climatic conditions existing in the 

 storage area throughout the continental United States. In controlling these in- 

 sects, it is recommended that fumigation immediately follow the peak of emer- 

 gence. This time is determined from catches obtained in suction light traps, 

 installed as shown in figure 2. The average life cycle of these insects is from 50 

 to 60 days. 



It is essential, therefore, that sealing in warehouses must be maintained for 

 periods up to 7 months in each year. As the cost is high, it is desirable that the 

 type of sealing used be durable and easy to patch at the beginning of the next 

 fumigation season. 



Fumigation and Sealing Problems 



Hydrogen cyanide (HCN), a fumigant recommended by the Department and 

 used extensively throughout the tobacco industry, is slighdy lighter than air. Any 

 very small aperture resulting from inadequate sealing will permit leakage which 

 will reduce the concentration of gas in the building. As the insects to be destroyed 

 are usually not active at temperatures below 60 ° F. and as fumigants are gen- 

 erally more effective at temperatures above this point, the retention of heat within 

 the building is not an important point. Leakage of gas caused by high winds 

 or other detrimental atmospheric conditions presents a much greater problem due 

 to the effect on the distribution and density of gas within the building. 



