Circular No. 173. Issued May 27, 1913. 



United States Department of Agriculture, 



BUREAU OF ENTOMOLOGY. 

 L. O. HOWARD, Entomologist and Chief of Bureau. 



ARSENATE OF LEAD AS AN INSECTICIDE AGAINST THE 

 TOBACCO HORNWORMS. 



By A. C. Morgan and D. C. Pabman, 



Entomological Assistants. 



INTRODUCTORY. 



During the past five years the Bureau of Entomology has been 

 conducting an investigation of tobacco insects in Tennessee and 

 Kentucky and in some of the adjoining States. In Tennessee the 

 bureau has been very materially assisted by Prof. H. A. Morgan, 

 director of the Tennessee Agricultural Experiment Station. 



In the dark-tobacco districts of Kentucky and Tennessee tobacco 

 homworms are the ever-present and most serious problem of the 

 tobacco grower. Ten to twelve years ago, when labor was plentiful, 

 cheap, and efficient, "hand-worming" was found to be economical 

 and effective in combating this pest. However, during the last six or 

 eight years hand-worming has become too costly, because of the 

 great scarcity of labor, and too inefficient, and the growers have been 

 forced to employ an insecticide. At the time insecticides were first 

 used Paris green was found to be the safest and most efficient. Nev- 

 ertheless, there has always been complaint of frequent serious burn- 

 ing of tobacco as a result of its use. To find a safe and effective 

 insecticide has been one of the main lines of investigation by the 

 writers during the past five years. Di-plumbic arsenate of lead has 

 been found to meet the requirements. In the further discussion of 

 this subject the use and action of Paris green will be rather thor- 

 oughly discussed in connection with the use and action of arsenate 

 of lead, for the reason that since the insecticidal results of the use of 

 Paris green are so well known it will be easier to explain the value 

 of arsenate of lead if it be compared with this well-known poison. 

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