BUREAU OF ENTOMOLOGY. 319 



of experimental models of this type of machine. The advantages 

 of the shaftless type over the shaft type of two-ro\v duster lie in the 

 fact of the lower center of gravity and the fact that it can be turned 

 in half the space required by the shaft type. It is also thought that 

 the cost of construction will be le.ss than that of the shaft duster. 



The mo.st severe outbreak of crambids ('' screw worms") on record 

 for this region occurred this year. Many tobacco fields had to be 

 almost completely reset twice. A large number of other fields were 

 so badly infested that two and even three lieavy replantings were 

 necessary. Two species were about equally concerned in the injury, 

 Cramhus caliginoselJii.<< and Arrolof'hvs popeaneUus. A poisoned 

 bait containing an attractant. the first direct remedy on record, was 

 found to give a control of 8^ to 89 per cent on caliginoseUus in some 

 experiments and a control of sO to 93 per cent in other experiments. 

 However, further experimentation is necessary before exact methods 

 of application should be advised. 



The work upon the life history of the tobacco flea-beetle at Quincy. 

 Fla.. mentioned in the last report, has shown ver\- satisfactory 

 progress. In addition to three generations in direct line, the number 

 of larval instars has also been determined and control work has been 

 continued and improved upon. The tobacco thrips were scarce again, 

 and notliing more than preliminary experiments with nicotine dusts 

 could be performed. 



A preliminary survey of the tobacco-insect problems of the Burley 

 tobacco belt has been made, and a great lack of adequate and eco- 

 nomical methods of control found. Arrangements have been made 

 for a few large-scale field experiments upon hornworm control in 

 this region. 



Sugar-cane and rice insects. — The tachinid parasite, introduced 

 from Cuba and released upon various plantations for the purpose of 

 controlling the sugar-cane borer, was found in the fall of 1921 on 18 

 plantations scattered throughout the sugar parishes of Louisiana. 

 Upon IT of these plantations it had endured one winter, and in one 

 place it had lived over two winters. It is expected that the parasite 

 will increase at these centers and gradually spread over the entire 

 sugar section. 



In addition to the Cuban parasite, specimens of a braconid para- 

 site brouofht to this countrv from southern France to control the 

 European corn borer were sent to the sugar-cane insect laboratory- at 

 Xew Orleans. It was not known whether they would attack the 

 sugar-cane moth borer, but they were found to do so readily and to 

 breed on it successfully. These parasites are at present being released 

 at onlv one plantation. Iiut it is planned to release them generally 

 if favorable results are obtained upon this plantation. 



Control work on the moth borer is not confined to parasite intro- 

 duction, but experiments are being conducted with various chemi- 

 cals to test their efficiency in killing the larvse in the seed cane after 

 plantifig. This work infludes tests with paradichlorobenzene, 

 which has given good results in control of the peach-tree borer. A 

 number of chemicals not previously used as insecticides are being 

 tested. 



A new lepidopterous larva, boring in sugar cane, has been found 

 along the ^lississippi coast, inspections having been made by an 

 agent of this bureau cooperating with the ^lississippi plant board. 



