UNITED STATES DEPARTMENT OF AGRICULTURE 



J\Jy^mfU 



% BULLETIN No. 731 



Contribution from the Bureau of Entomology, 

 L. O. HOWARD, Chief. 



Washington, D. C. 



July 19, 1918 



RECENT EXPERIMENTAL WORK ON POISONING 

 COTTON-BOLL WEEVILS. 1 



By B. R. Co ad, 



Entomological Assistant, Southern Field-Crop Insect Investigations, Bureau of 



Entomology. 



CONTENTS. 



Page. 



Early attempts at poisoning the weevil : 1 



The water-drinking habit of the weevil and 



its hearing on poisoning 2 



The poisoning tests of 1915 2 



Poisoning experiments in 1916 3 



Experiments in 1917 6 



Laboratory and other experiments 10 



Importance of moisture in poisoning 11 



Page. 



Relative effectiveness of different arsenicals. . 11 



Density of the poison 12 



Time of applications 13 



Machinery for applying the poison 1-1 



Amount of poison per application 14 



Number of applications 14 



Cost of treatment 15 



Necessity for further experimental work 15 



EARLY ATTEMPTS AT POISONING THE WEEVIL. 



Practically since the advent of the Mexican cotton-boll weevil 

 innumerable attempts have been made to control this pest by the 

 use of poisons. The results, however, were always discouraging. 

 The best that could be secured apparently was a very slight degree 

 of control which would seldom pay for the expense of treatment. 

 As a result it was generally conceded- that the weevil could not be 

 poisoned profitably under cotton-field conditions. This was attrib- 

 uted to the fact that the weevil derived its food from deep punc- 

 tures which it made into the cotton squares and bolls, thus 

 ingesting very little of the external plant tissues upon which the 

 poison would be found. On account of this feeding habit of the 

 weevil the idea prevailed that the only possible method of poisoning 

 would be one which would so distribute the poison on the plant that 

 small amounts would be eaten during the process of starting the punc- 

 tures through the external tissues. For this reason all experiments 

 were aimed toward getting a poison which could be driven inside the 



i In the development of power machinery for applying the poison Mr. Elmer Johnson, of the Bureau of 

 Public Roads, has been of inestimable assistance. 

 70524°— 18— Bull. 731 1 



