UNITED STATES DEPARTMENT OF AGRICULTURE 
+N; BULLETIN No. 731 ¥ 
Contribution from the Bureau of Entomology, 
PIF WefL. L. O. HOWARD, Chief. 
Washington, D. C. WV July 19, 1918 
RECENT EXPERIMENTAL WORK ON POISONING 
COTTON-BOLL WEEVILS.’ 
By B. R. Coan, 
Fintomological Assistant, Southern Field-Crop Insect Investigations, Bureau of 
Entomology. 
CONTENTS. 
Page. Page. 
Early attempts at poisoning the weevil...... 1 | Relative effectiveness of different arsenicals. 11 
The water-drinking habit of the weevil and DenSiiiynol-tMerp OlISOMese saa ae eee eee 12 
HUSH Galo OM WOISOMIN Sse sae aoe se ee = 27a oe NE OIA LCA OMS essen See eae eee 13 
MhHempoisoniMesvests Gill aee ses eke eee le 2 | Machinery for applying the poison..........- 14 
Rosoningsexperiments 1mdOlG S22 a .5. os - 3 | Amount of poison per application............ i4 
ID Sxperemoneraniss wo TONGS ee ss Ge ee oe sy Oe a eNTIMIbeEOhappiMCahlOnStss. 4444s ens. See 14 
Laboratery and other experiments....--.-.-- LOR ECostioi treatment ess cans eee ere ee ere 15 
Importance of moisture in poisoning. ........ 11 | 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 
1In 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 
