BIOLOGY OF TOBACCO MOTH AND ITS CONTROL 29 



moths was 7 for the weeks ended October 10 and 17. Although the 

 tobacco moth is not positively phototropic to a high degree, it has 

 been determined 4 that light traps of the type described above were 

 satisfactory for indicating the progress of emergence and the dates 

 for periodic fumigations. Since it has been recommended that fumi- 

 gations be carried out in warehouses when the average catch of 

 moths reaches 30 per week, all of the fumigations after June 1 were 





Figure 20. — Cylinders of hydrocyanic acid and air compressors used in connection with 

 the fumigation of warehouses for control of the tobacco moth in 1932. The copper 

 pipes entering the warehouse through the brick wall can be seen on the rear wall at 

 the right. 



conducted when moth infestations were probably below the point 

 of economic damage. It is believed, therefore, that the fumigation 

 made on June 28 could have been delayed and that three fumigations 

 during the season of 1932 would have sufficed to hold the tobacco 

 moth under control. 



FACTORS INFLUENCING RESULTS IN WAREHOUSE FUMIGATIONS 

 DOSAGE, TEMPERATURE, AND PERIOD OF EXPOSURE 



The dosage, temperature, and exposure were all found to be of im- 

 portance in obtaining satisfactory results in controlling the tobacco 

 moth by periodic fumigations at atmospheric pressure in closed to- 

 bacco warehouses. During experiments in 1930, 1931, and 1932, the 

 writers used dosages of hydrocyanic acid ranging from 1 to 24 

 ounces per 1,000 cubic feet of storage space. 4 It was concluded 



4 Reed, W. D., Livingstone, E. M., and Morrill, A. W., Jr. the fumigation of to- 

 bacco warehouses. U. S. Dept. Agr., Bur. Ent. and Plant Quarantine Circ. E-325, illus. 

 1934. [Mimeographed.] 



