BUREAU OF ENTOMOLOGY. 625 



WORK ON INSECTS INJURIOUS TO SOUTHERN FIELD CROPS. 



The work on insects injurious to southern field crops dealt with six 

 specific lines of investigation, as follows: (1) Cotton-boll weevil; 

 (2) tobacco insects; (3) sugar-cane insects; (4) the Argentine ant; 

 (5) rice insects; (6) the cotton red spider. In addition several mis- 

 cellaneous problems received attention. The work of this section 

 has been carried on as before under the supervision of Mr. W. D. 

 Hunter. 



THE COnON-BOLL WEEVIL. 



The work on the cotton-boll weevil problem consisted of the testing 

 of control measures, both direct and indirect, such as the encourage- 

 ment of parasitic enemies; the determination of the status of the 

 insect from time to time throughout its range; the mapping of the 

 new territory invaded; and various incidental matters. 



The experiments in practical control were conducted largely in the 

 Mississippi-Yazoo Delta, where a laboratory was maintained through- 

 out the season. On typical plantations in this region extensive series 

 of tests were instituted to determine the value of hand picking the 

 early appearing weevils and the infested squares. Some years ago 

 the practice was tested thoroughly in Texas, with the result that it 

 appeared to be extremely doubtful whether the benefit to the crop 

 would ever offset the expense involved. In Louisiana and Missis- 

 sippi, with conditions quite different from those in Texas, the prac- 

 tice may be found to be more feasible. The experiments of the sea- 

 son dealt with pickings beginning at different dates in the spring, 

 continuing to different dates in the summer, and with different time 

 intervals between the pickings. The work was designed to deter- 

 mine at what date the work could be begun to advantage and when it 

 should be discontinued, and also whether a period of 5, 7, or 10 days 

 between the pickings would be the most advantageous. The experi- 

 ments were conducted under practical conditions on different planta- 

 tions and supplied a large amount of data. The work of the season, 

 taken in connection with results obtained previously and others that 

 will be secured, will show accurately what may be done by this prac- 

 tice under different conditions of season and plantation management. 



The experiments to detemiine whether the burial of the cotton 

 stalks or the infested squares can be depended upon to take the place 

 of the burning of the stalks were continued. As in the square-pick- 

 ing experiments, this work was conducted on several plantations in 

 the heavily infested territory. It was found that within certain 

 limits approximately the same results as follow from burning of the 

 plants could be obtained by deep plowing. This was noticeably the 

 case in plowing under the infested squares at the time the weevils 

 become so numerous as to destroy all of the fruit as it formed. The 

 value of the process depends upon local conditions of soil and rain- 

 fall. The results of the season's work add considerable definiteness 

 to the information that has been available hitherto and promise to 

 show one method whereby the loss of organic matter incident to the 

 burning of the stalks may be avoided. 



Experiments in poisoning the boll weevil by means of powdered 

 arsenate of lead and other areenicals were conducted on several plan- 



70481"— AQB 1912 40. 



