26 CIRCULAR 4 2 2, U. S. DEPARTMENT OF AGRICULTURE 



CONTROL EXPERIMENTS OF 1932 



PRELIMINARY TESTS 



Experiments in warehouses infested by the tobacco moth were car- 

 ried out in 1930 and 1931 which showed that if this pest is to be 

 held under control by atmospheric fumigation, a program of periodic 

 fumigations must be devised. The experiments showed that it was 

 rarely possible to obtain complete control of the tobacco moth from 

 one fumigation at atmospheric pressure, regardless of the dosage of 

 fumigant applied. A series of experiments was then outlined to 

 fumigate 3,318,000 cubic feet of storage space (figs. 12 and 13) in 

 which tobaccos were stored valued at approximately $10,000,000. The 

 infested warehouses were divided by brick fire walls into sections each 

 containing about 200,000 cubic feet, and one sprav nozzle was installed 

 for each 30,000 cubic feet. 



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Figure 18. — A gasproof tar paper used for sealing the entire window space in a tobacco 



warehouse. 



LIGHT-TRAP INDICATORS 



On April 11, 1932, light traps, in which a sticky fly paper was used, 

 were placed in the warehouses. Each of these traps consisted of a 

 fabricated board 16 inches long, 10 inches wide, and three-eighths of 

 an inch thick, on which a sheet- of sticky fly paper was fastened with 

 thumbtacks. They were suspended at an angle of 45° about 6 inches 

 below electric lights (fig. 21). One such trap indicator was installed 

 for about each 97,000 cubic feet of storage space. The tobacco moth 

 was not positively phototropic to a high degree, but the catches of 

 moths on these indicators served very satisfactorily as a guide in 

 scheduling the periodic fumigations. 



