BUREAU OF ENTOMOLOGY. 627 



TOBACCO INSECT IflVKSTIGATIONS. 



The principnl work on tobacco insects consisted of investigations 

 of means of control of the so-called hornworms and demonstrations 

 based thereon, the demonstration of methods of control of the to- 

 bacco wireworm in Virginia, a study of the control of the cigarette 

 beetle, and a preliminary investigation of the causation of the so- 

 called mosaic disease of tobacco by insects. The main work of the 

 investigations was conducted at Clarksville, Tenn., while the work 

 on the wireworm was centered largely at Appomattox, Va. 



The principal work on the hornworm was designed to furnish sat- 

 isfactory means of control by chemicals. A large number of arsen- 

 ical preparations were tested. In several instances these prepara- 

 tions were made up especially for the bureau by manufacturing chem- 

 ists. It was fully determined and demonstrated on a small scale that 

 arsenate of lead is an almost perfect remedy for the hornworm. This 

 discovery will eventually cause the discontinuance of the use of Paris 

 green, which, though generally used, has been found to do damage to 

 the tobacco that has not been appreciated. In this work indications 

 were obtained that poisons even more satisfactory than arsenate of 

 lead may be found as the result of future investigations. 



The demonstrational work, which was necessarily conducted on a 

 small scale on account of the shortage of funds, was well received by 

 the planters and will undoubtedly result in the adoption of greatly 

 improved methods. 



The work on the cigarette beetle revealed the fact that the pest is 

 of considerably more importance than has been supposed. It was 

 possible to utilize only a small portion of the time of one agent on 

 this work. As opportunities arose, however, experiments wdth differ- 

 ent fumigants and in attracting the beetles by various means in the 

 warehouses were instituted. 



The work on the tobacco wireworm in Virginia was restricted 

 largely to the investigation of means of direct control and demonstra- 

 tions. All experiments and observations have shown that the most 

 effective control consists of freeing land from such weeds as are the 

 natural food plants of the insects. It was found that this could be 

 brought about by several methods. One of them is a proper rotation 

 of crops; another, the summer plowing of the fields; and another, 

 the use of lime. In the experiments with lime it was found that 

 sheep sorrel, one of the plants upon which the wireworm breeds in 

 great abundance, would not grow where even a comparatively small 

 amount of the substance had been applied. The lime also had a re- 

 markable effect in decreasing the number of other natural food plants* 

 of the wireworm. These results will form a foundation for a system 

 of control that will be well adapted to the conditions in the tobacco 

 regions of Virginia, A large number of experiments with insecti- 

 cides against the wireworm were conducted, but without satisfactory 

 outcome. 



SUGAR-CANE INSECT INVESTIGATIONS. 



The work of the investigation of sugar-cane insects dealt largely 

 with th*e borer, which is by far tlie most important enemy of the crop 

 in the United States. It has been supposed that this species attacks 



