THE BOLL WEEVIL — LOFTIN 283 



carpel lining offer some resistance to weevil puncture, but no varieties 

 have been found with bolls that weevils cannot pierce. 



DEVELOPMENT OP INSECTICIDAL CONTIiOL 



The insecticides and methods of application available to entomolo- 

 gists 50 years ago were very limited. Most of the insecticides then in 

 use were applied as sprays with crude machinery and gave poor or no 

 weevil control. Early tests showed that paris green, which had re- 

 cently come into use, killed some of the adults, but the control was 

 not sufficient to materially increase yields. Lead arsenate in paste 

 form was later found to kill some of the weevils but could be applied 

 only as a spray, which was not very practicable for cotton. Various 

 other materials were likewise found of little value, and for 20 years 

 the search for an effective insecticide for the boll weevil was unsuc- 

 cessful. In 1908 Wilmon Newell, entomologist of the Louisiana Crop 

 Commission, stimulated new interest in insecticidal control by intro- 

 ducing lead arsenate in powder form for dusting cotton for boll-weevil 

 control. This dust gave better weevil control than any material pre- 

 viously tested, but the results were erratic and it was never exten- 

 sively used. However, his work was responsible for the development 

 and later extensive use of insecticides in dust form for many insects. 

 The next important step in insecticidal control of weevils came in 

 1916, when B. R. Coad, of the Bureau of Entomology, found that 

 keeping the cotton plants thoroughly covered with an arsenical dust 

 throughout the growing season would kill adult weevils and that 

 calcium arsenate was the most effective of the many materials tested. 

 Calcium arsenate was then a new material that had been tested in a 

 limited way for fruit and shade-tree insects but was not available in 

 commercial quantities. Extensive experiments were started to im- 

 prove its chemical and physical properties and methods of application 

 for weevil control. In the 1917 experiments the increase in yields 

 from fields dusted with calcium arsenate were so outstanding that in 

 1918, 35,000 acres of cotton were dusted under Bureau of Entomology 

 supervision. Specifications were developed and manufacturers were 

 aided in making calcium arsenate to meet the rapidly increasing de- 

 mands. Much of the early calcium arsenate was of poor dusting 

 quality and caused serious burning of the plants, and much effort was 

 expended by the Bureau and State experiment stations during the fol- 

 lowing years in overcoming these defects. Grower response was imme- 

 diate, and over 3 million pounds of calcium arsenate were used for 

 weevil control in 1919, 10 million pounds in 1920, and 60 to 70 million 

 pounds have been manufactured annually during recent years. 



